Re: [PATCH v3 01/11] stm class: Introduce an abstraction for System Trace Module devices

[Mathieu Poirier]

On 6 July 2015 at 04:08, Alexander Shishkin
<alexander.shishkin@xxxxxxxxxxxxxxx> wrote:
> A System Trace Module (STM) is a device exporting data in System Trace
> Protocol (STP) format as defined by MIPI STP standards. Examples of such
> devices are Intel Trace Hub and Coresight STM.
>
> This abstraction provides a unified interface for software trace sources
> to send their data over an STM device to a debug host. In order to do
> that, such a trace source needs to be assigned a pair of master/channel
> identifiers that all the data from this source will be tagged with. The
> STP decoder on the debug host side will use these master/channel tags to
> distinguish different trace streams from one another inside one STP
> stream.
>
> This abstraction provides a configfs-based policy management mechanism
> for dynamic allocation of these master/channel pairs based on trace
> source-supplied string identifier. It has the flexibility of being
> defined at runtime and at the same time (provided that the policy
> definition is aligned with the decoding end) consistency.
>
> For userspace trace sources, this abstraction provides write()-based and
> mmap()-based (if the underlying stm device allows this) output mechanism.
>
> For kernel-side trace sources, we provide "stm_source" device class that
> can be connected to an stm device at run time.
>
> Cc: linux-api@xxxxxxxxxxxxxxx
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> ---
>  Documentation/ABI/testing/configfs-stp-policy    |   48 +
>  Documentation/ABI/testing/sysfs-class-stm        |   14 +
>  Documentation/ABI/testing/sysfs-class-stm_source |   11 +
>  Documentation/ioctl/ioctl-number.txt             |    3 +
>  Documentation/trace/stm.txt                      |   80 ++
>  drivers/Kconfig                                  |    2 +
>  drivers/Makefile                                 |    1 +
>  drivers/hwtracing/stm/Kconfig                    |    8 +
>  drivers/hwtracing/stm/Makefile                   |    3 +
>  drivers/hwtracing/stm/core.c                     | 1029 ++++++++++++++++++++++
>  drivers/hwtracing/stm/policy.c                   |  529 +++++++++++
>  drivers/hwtracing/stm/stm.h                      |   87 ++
>  include/linux/stm.h                              |  126 +++
>  include/uapi/linux/stm.h                         |   50 ++
>  14 files changed, 1991 insertions(+)
>  create mode 100644 Documentation/ABI/testing/configfs-stp-policy
>  create mode 100644 Documentation/ABI/testing/sysfs-class-stm
>  create mode 100644 Documentation/ABI/testing/sysfs-class-stm_source
>  create mode 100644 Documentation/trace/stm.txt
>  create mode 100644 drivers/hwtracing/stm/Kconfig
>  create mode 100644 drivers/hwtracing/stm/Makefile
>  create mode 100644 drivers/hwtracing/stm/core.c
>  create mode 100644 drivers/hwtracing/stm/policy.c
>  create mode 100644 drivers/hwtracing/stm/stm.h
>  create mode 100644 include/linux/stm.h
>  create mode 100644 include/uapi/linux/stm.h
>
> diff --git a/Documentation/ABI/testing/configfs-stp-policy b/Documentation/ABI/testing/configfs-stp-policy
> new file mode 100644
> index 0000000000..421ce6825c
> --- /dev/null
> +++ b/Documentation/ABI/testing/configfs-stp-policy
> @@ -0,0 +1,48 @@
> +What:          /config/stp-policy
> +Date:          June 2015
> +KernelVersion: 4.3
> +Description:
> +               This group contains policies mandating Master/Channel allocation
> +               for software sources wishing to send trace data over an STM
> +               device.
> +
> +What:          /config/stp-policy/<device>.<policy>
> +Date:          June 2015
> +KernelVersion: 4.3
> +Description:
> +               This group is the root of a policy; its name is a concatenation
> +               of an stm device name to which this policy applies and an
> +               arbitrary string. If <device> part doesn't match an existing
> +               stm device, mkdir will fail with ENODEV; if that device already
> +               has a policy assigned to it, mkdir will fail with EBUSY.
> +
> +What:          /config/stp-policy/<device>.<policy>/device
> +Date:          June 2015
> +KernelVersion: 4.3
> +Description:
> +               STM device to which this policy applies, read only. Same as the
> +               <device> component of its parent directory.
> +
> +What:          /config/stp-policy/<device>.<policy>/<node>
> +Date:          June 2015
> +KernelVersion: 4.3
> +Description:
> +               Policy node is a string identifier that software clients will
> +               use to request a master/channel to be allocated and assigned to
> +               them.
> +
> +What:          /config/stp-policy/<device>.<policy>/<node>/masters
> +Date:          June 2015
> +KernelVersion: 4.3
> +Description:
> +               Range of masters from which to allocate for users of this node.
> +               Write two numbers: the first master and the last master number.
> +
> +What:          /config/stp-policy/<device>.<policy>/<node>/channels
> +Date:          June 2015
> +KernelVersion: 4.3
> +Description:
> +               Range of channels from which to allocate for users of this node.
> +               Write two numbers: the first channel and the last channel
> +               number.
> +
> diff --git a/Documentation/ABI/testing/sysfs-class-stm b/Documentation/ABI/testing/sysfs-class-stm
> new file mode 100644
> index 0000000000..c9aa4f3fc9
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-stm
> @@ -0,0 +1,14 @@
> +What:          /sys/class/stm/<stm>/masters
> +Date:          June 2015
> +KernelVersion: 4.3
> +Contact:       Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> +Description:
> +               Shows first and last available to software master numbers on
> +               this STM device.
> +
> +What:          /sys/class/stm/<stm>/channels
> +Date:          June 2015
> +KernelVersion: 4.3
> +Contact:       Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> +Description:
> +               Shows the number of channels per master on this STM device.
> diff --git a/Documentation/ABI/testing/sysfs-class-stm_source b/Documentation/ABI/testing/sysfs-class-stm_source
> new file mode 100644
> index 0000000000..57b8dd39bb
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-stm_source
> @@ -0,0 +1,11 @@
> +What:          /sys/class/stm_source/<stm_source>/stm_source_link
> +Date:          June 2015
> +KernelVersion: 4.3
> +Contact:       Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> +Description:
> +               stm_source device linkage to stm device, where its tracing data
> +               is directed. Reads return an existing connection or "<none>" if
> +               this stm_source is not connected to any stm device yet.
> +               Write an existing (registered) stm device's name here to
> +               connect that device. If a device is already connected to this
> +               stm_source, it will first be disconnected.
> diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
> index 611c52267d..7fa29b4ece 100644
> --- a/Documentation/ioctl/ioctl-number.txt
> +++ b/Documentation/ioctl/ioctl-number.txt
> @@ -81,6 +81,9 @@ Code  Seq#(hex)       Include File            Comments
>  0x22   all     scsi/sg.h
>  '#'    00-3F   IEEE 1394 Subsystem     Block for the entire subsystem
>  '$'    00-0F   linux/perf_counter.h, linux/perf_event.h
> +'%'    00-0F   include/uapi/linux/stm.h
> +                                       System Trace Module subsystem
> +                                       <mailto:alexander.shishkin@xxxxxxxxxxxxxxx>
>  '&'    00-07   drivers/firewire/nosy-user.h
>  '1'    00-1F   <linux/timepps.h>       PPS kit from Ulrich Windl
>                                         <ftp://ftp.de.kernel.org/pub/linux/daemons/ntp/PPS/>
> diff --git a/Documentation/trace/stm.txt b/Documentation/trace/stm.txt
> new file mode 100644
> index 0000000000..e140f2e8d7
> --- /dev/null
> +++ b/Documentation/trace/stm.txt
> @@ -0,0 +1,80 @@
> +System Trace Module
> +===================
> +
> +System Trace Module (STM) is a device described in MIPI STP specs as
> +STP trace stream generator. STP (System Trace Protocol) is a trace
> +protocol multiplexing data from multiple trace sources, each one of
> +which is assigned a unique pair of master and channel. While some of
> +these masters and channels are statically allocated to certain
> +hardware trace sources, others are available to software. Software
> +trace sources are usually free to pick for themselves any
> +master/channel combination from this pool.
> +
> +On the receiving end of this STP stream (the decoder side), trace
> +sources can only be identified by master/channel combination, so in
> +order for the decoder to be able to make sense of the trace that
> +involves multiple trace sources, it needs to be able to map those
> +master/channel pairs to the trace sources that it understands.
> +
> +For instance, it is helpful to know that syslog messages come on
> +master 7 channel 15, while arbitrary user applications can use masters
> +48 to 63 and channels 0 to 127.
> +
> +To solve this mapping problem, stm class provides a policy management
> +mechanism via configfs, that allows defining rules that map string
> +identifiers to ranges of masters and channels. If these rules (policy)
> +are consistent with what decoder expects, it will be able to properly
> +process the trace data.
> +
> +This policy is a tree structure containing rules (policy_node) that
> +have a name (string identifier) and a range of masters and channels
> +associated with it, located in "stp-policy" subsystem directory in
> +configfs. The topmost directory's name (the policy) is formatted as
> +the STM device name to which this policy applies and and arbitrary
> +string identifier separated by a stop. From the examle above, a rule
> +may look like this:
> +
> +$ ls /config/stp-policy/dummy_stm.my-policy/user
> +channels masters
> +$ cat /config/stp-policy/dummy_stm.my-policy/user/masters
> +48 63
> +$ cat /config/stp-policy/dummy_stm.my-policy/user/channels
> +0 127
> +
> +which means that the master allocation pool for this rule consists of
> +masters 48 through 63 and channel allocation pool has channels 0
> +through 127 in it. Now, any producer (trace source) identifying itself
> +with "user" identification string will be allocated a master and
> +channel from within these ranges.
> +
> +These rules can be nested, for example, one can define a rule "dummy"
> +under "user" directory from the example above and this new rule will
> +be used for trace sources with the id string of "user/dummy".
> +
> +Trace sources have to open the stm class device's node and write their
> +trace data into its file descriptor. In order to identify themselves
> +to the policy, they need to do a STP_POLICY_ID_SET ioctl on this file
> +descriptor providing their id string. Otherwise, they will be
> +automatically allocated a master/channel pair upon first write to this
> +file descriptor according to the "default" rule of the policy, if such
> +exists.
> +
> +Some STM devices may allow direct mapping of the channel mmio regions
> +to userspace for zero-copy writing. One mappable page (in terms of
> +mmu) will usually contain multiple channels' mmios, so the user will
> +need to allocate that many channels to themselves (via the
> +aforementioned ioctl() call) to be able to do this. That is, if your
> +stm device's channel mmio region is 64 bytes and hardware page size is
> +4096 bytes, after a successful STP_POLICY_ID_SET ioctl() call with
> +width==64, you should be able to mmap() one page on this file
> +descriptor and obtain direct access to an mmio region for 64 channels.
> +
> +For kernel-based trace sources, there is "stm_source" device
> +class. Devices of this class can be connected and disconnected to/from
> +stm devices at runtime via a sysfs attribute.
> +
> +Examples of STM devices are Intel Trace Hub [1] and Coresight STM
> +[2].
> +
> +[1] https://software.intel.com/sites/default/files/managed/d3/3c/intel-th-developer-manual.pdf
> +[2] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0444b/index.html
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index 6e973b8e3a..96efe4522c 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -184,4 +184,6 @@ source "drivers/android/Kconfig"
>
>  source "drivers/nvdimm/Kconfig"
>
> +source "drivers/hwtracing/stm/Kconfig"
> +
>  endmenu
> diff --git a/drivers/Makefile b/drivers/Makefile
> index b64b49f6e0..6647bc923f 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -164,4 +164,5 @@ obj-$(CONFIG_MCB)           += mcb/
>  obj-$(CONFIG_RAS)              += ras/
>  obj-$(CONFIG_THUNDERBOLT)      += thunderbolt/
>  obj-$(CONFIG_CORESIGHT)                += hwtracing/coresight/
> +obj-$(CONFIG_STM)              += hwtracing/stm/
>  obj-$(CONFIG_ANDROID)          += android/
> diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig
> new file mode 100644
> index 0000000000..90ed327461
> --- /dev/null
> +++ b/drivers/hwtracing/stm/Kconfig
> @@ -0,0 +1,8 @@
> +config STM
> +       tristate "System Trace Module devices"
> +       help
> +         A System Trace Module (STM) is a device exporting data in System
> +         Trace Protocol (STP) format as defined by MIPI STP standards.
> +         Examples of such devices are Intel Trace Hub and Coresight STM.
> +
> +         Say Y here to enable System Trace Module device support.
> diff --git a/drivers/hwtracing/stm/Makefile b/drivers/hwtracing/stm/Makefile
> new file mode 100644
> index 0000000000..adec701649
> --- /dev/null
> +++ b/drivers/hwtracing/stm/Makefile
> @@ -0,0 +1,3 @@
> +obj-$(CONFIG_STM)      += stm_core.o
> +
> +stm_core-y             := core.o policy.o
> diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
> new file mode 100644
> index 0000000000..b79c42c625
> --- /dev/null
> +++ b/drivers/hwtracing/stm/core.c
> @@ -0,0 +1,1029 @@
> +/*
> + * System Trace Module (STM) infrastructure
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * STM class implements generic infrastructure for  System Trace Module devices
> + * as defined in MIPI STPv2 specification.
> + */
> +
> +#include <linux/uaccess.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/compat.h>
> +#include <linux/kdev_t.h>
> +#include <linux/srcu.h>
> +#include <linux/slab.h>
> +#include <linux/stm.h>
> +#include <linux/fs.h>
> +#include <linux/mm.h>
> +#include "stm.h"
> +
> +#include <uapi/linux/stm.h>
> +
> +static unsigned int stm_core_up;
> +
> +/*
> + * The SRCU here makes sure that STM device doesn't disappear from under a
> + * stm_source_write() caller, which may want to have as little overhead as
> + * possible.
> + */
> +static struct srcu_struct stm_source_srcu;
> +
> +static ssize_t masters_show(struct device *dev,
> +                           struct device_attribute *attr,
> +                           char *buf)
> +{
> +       struct stm_device *stm = to_stm_device(dev);
> +       int ret;
> +
> +       ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);
> +
> +       return ret;
> +}
> +
> +static DEVICE_ATTR_RO(masters);
> +
> +static ssize_t channels_show(struct device *dev,
> +                            struct device_attribute *attr,
> +                            char *buf)
> +{
> +       struct stm_device *stm = to_stm_device(dev);
> +       int ret;
> +
> +       ret = sprintf(buf, "%u\n", stm->data->sw_nchannels);
> +
> +       return ret;
> +}
> +
> +static DEVICE_ATTR_RO(channels);
> +
> +static struct attribute *stm_attrs[] = {
> +       &dev_attr_masters.attr,
> +       &dev_attr_channels.attr,
> +       NULL,
> +};
> +
> +ATTRIBUTE_GROUPS(stm);
> +
> +static struct class stm_class = {
> +       .name           = "stm",
> +       .dev_groups     = stm_groups,
> +};
> +
> +static int stm_dev_match(struct device *dev, const void *data)
> +{
> +       const char *name = data;
> +
> +       return sysfs_streq(name, dev_name(dev));
> +}
> +
> +/**
> + * stm_find_device() - find stm device by name
> + * @buf:       character buffer containing the name
> + *
> + * This is called when either policy gets assigned to an stm device or an
> + * stm_source device gets linked to an stm device.
> + *
> + * This grabs device's reference (get_device()) and module reference, both
> + * of which the calling path needs to make sure to drop with stm_put_device().
> + *
> + * Return:     stm device pointer or null if lookup failed.
> + */
> +struct stm_device *stm_find_device(const char *buf)
> +{
> +       struct stm_device *stm;
> +       struct device *dev;
> +
> +       if (!stm_core_up)
> +               return NULL;
> +
> +       dev = class_find_device(&stm_class, NULL, buf, stm_dev_match);
> +       if (!dev)
> +               return NULL;
> +
> +       stm = to_stm_device(dev);
> +       if (!try_module_get(stm->owner)) {
> +               put_device(dev);
> +               return NULL;
> +       }
> +
> +       return stm;
> +}
> +
> +/**
> + * stm_put_device() - drop references on the stm device
> + * @stm:       stm device, previously acquired by stm_find_device()
> + *
> + * This drops the module reference and device reference taken by
> + * stm_find_device().
> + */
> +void stm_put_device(struct stm_device *stm)
> +{
> +       module_put(stm->owner);
> +       put_device(&stm->dev);
> +}
> +
> +/*
> + * Internally we only care about software-writable masters here, that is the
> + * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
> + * original master numbers to be visible externally, since they are the ones
> + * that will appear in the STP stream. Thus, the internal bookkeeping uses
> + * $master - stm_data->sw_start to reference master descriptors and such.
> + */
> +
> +#define __stm_master(_s, _m)                           \
> +       ((_s)->masters[(_m) - (_s)->data->sw_start])
> +
> +static inline struct stp_master *
> +stm_master(struct stm_device *stm, unsigned int idx)
> +{
> +       if (idx < stm->data->sw_start || idx > stm->data->sw_end)
> +               return NULL;
> +
> +       return __stm_master(stm, idx);
> +}
> +
> +static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
> +{
> +       struct stp_master *master;
> +       size_t size;
> +
> +       size = ALIGN(stm->data->sw_nchannels, 8) / 8;
> +       size += sizeof(struct stp_master);
> +       master = kzalloc(size, GFP_ATOMIC);
> +       if (!master)
> +               return -ENOMEM;
> +
> +       master->nr_free = stm->data->sw_nchannels;
> +       __stm_master(stm, idx) = master;
> +
> +       return 0;
> +}
> +
> +static void stp_master_free(struct stm_device *stm, unsigned int idx)
> +{
> +       struct stp_master *master = stm_master(stm, idx);
> +
> +       if (!master)
> +               return;
> +
> +       __stm_master(stm, idx) = NULL;
> +       kfree(master);
> +}
> +
> +static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
> +{
> +       struct stp_master *master = stm_master(stm, output->master);
> +
> +       if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
> +               return;
> +
> +       bitmap_allocate_region(&master->chan_map[0], output->channel,
> +                              ilog2(output->nr_chans));
> +
> +       master->nr_free -= output->nr_chans;
> +}
> +
> +static void
> +stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
> +{
> +       struct stp_master *master = stm_master(stm, output->master);
> +
> +       bitmap_release_region(&master->chan_map[0], output->channel,
> +                             ilog2(output->nr_chans));
> +
> +       output->nr_chans = 0;
> +       master->nr_free += output->nr_chans;
> +}
> +
> +/*
> + * This is like bitmap_find_free_region(), except it can ignore @start bits
> + * at the beginning.
> + */
> +static int find_free_channels(unsigned long *bitmap, unsigned int start,
> +                             unsigned int end, unsigned int width)
> +{
> +       unsigned int pos;
> +       int i;
> +
> +       for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
> +               pos = find_next_zero_bit(bitmap, end + 1, pos);
> +               if (pos + width > end + 1)
> +                       break;
> +
> +               if (pos & (width - 1))
> +                       continue;
> +
> +               for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
> +                       ;
> +               if (i == width)
> +                       return pos;
> +       }
> +
> +       return -1;
> +}
> +
> +static unsigned int
> +stm_find_master_chan(struct stm_device *stm, unsigned int width,
> +                    unsigned int *mstart, unsigned int mend,
> +                    unsigned int *cstart, unsigned int cend)
> +{
> +       struct stp_master *master;
> +       unsigned int midx;
> +       int pos, err;
> +
> +       for (midx = *mstart; midx <= mend; midx++) {
> +               if (!stm_master(stm, midx)) {
> +                       err = stp_master_alloc(stm, midx);
> +                       if (err)
> +                               return err;
> +               }
> +
> +               master = stm_master(stm, midx);
> +
> +               if (!master->nr_free)
> +                       continue;
> +
> +               pos = find_free_channels(master->chan_map, *cstart, cend,
> +                                        width);
> +               if (pos < 0)
> +                       continue;
> +
> +               *mstart = midx;
> +               *cstart = pos;
> +               return 0;
> +       }
> +
> +       return -ENOSPC;
> +}
> +
> +static int stm_output_assign(struct stm_device *stm, unsigned int width,
> +                            struct stp_policy_node *policy_node,
> +                            struct stm_output *output)
> +{
> +       unsigned int midx, cidx, mend, cend;
> +       int ret = -EINVAL;
> +
> +       if (width > stm->data->sw_nchannels)
> +               return -EINVAL;
> +
> +       if (policy_node) {
> +               stp_policy_node_get_ranges(policy_node,
> +                                          &midx, &mend, &cidx, &cend);
> +       } else {
> +               midx = stm->data->sw_start;
> +               cidx = 0;
> +               mend = stm->data->sw_end;
> +               cend = stm->data->sw_nchannels - 1;
> +       }
> +
> +       spin_lock(&stm->mc_lock);
> +       /* output is already assigned -- shouldn't happen */
> +       if (WARN_ON_ONCE(output->nr_chans))
> +               goto unlock;
> +
> +       ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
> +       if (ret)
> +               goto unlock;
> +
> +       output->master = midx;
> +       output->channel = cidx;
> +       output->nr_chans = width;
> +       stm_output_claim(stm, output);
> +       dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
> +
> +       ret = 0;
> +unlock:
> +       spin_unlock(&stm->mc_lock);
> +
> +       return ret;
> +}
> +
> +static void stm_output_free(struct stm_device *stm, struct stm_output *output)
> +{
> +       spin_lock(&stm->mc_lock);
> +       if (output->nr_chans)
> +               stm_output_disclaim(stm, output);
> +       spin_unlock(&stm->mc_lock);
> +}
> +
> +static int major_match(struct device *dev, const void *data)
> +{
> +       unsigned int major = *(unsigned int *)data;
> +
> +       return MAJOR(dev->devt) == major;
> +}
> +
> +static int stm_char_open(struct inode *inode, struct file *file)
> +{
> +       struct stm_file *stmf;
> +       struct device *dev;
> +       unsigned int major = imajor(inode);
> +       int err = -ENODEV;
> +
> +       dev = class_find_device(&stm_class, NULL, &major, major_match);
> +       if (!dev)
> +               return -ENODEV;
> +
> +       stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
> +       if (!stmf)
> +               return -ENOMEM;
> +
> +       stmf->stm = to_stm_device(dev);
> +
> +       if (!try_module_get(stmf->stm->owner))
> +               goto err_free;
> +
> +       file->private_data = stmf;
> +
> +       return nonseekable_open(inode, file);
> +
> +err_free:
> +       kfree(stmf);
> +
> +       return err;
> +}
> +
> +static int stm_char_release(struct inode *inode, struct file *file)
> +{
> +       struct stm_file *stmf = file->private_data;
> +
> +       stm_output_free(stmf->stm, &stmf->output);
> +       stm_put_device(stmf->stm);
> +       kfree(stmf);
> +
> +       return 0;
> +}
> +
> +static int stm_file_assign(struct stm_file *stmf, char *id, unsigned int width)
> +{
> +       struct stm_device *stm = stmf->stm;
> +       int ret;
> +
> +       stmf->policy_node = stp_policy_node_lookup(stm, id);
> +
> +       ret = stm_output_assign(stm, width, stmf->policy_node, &stmf->output);
> +
> +       if (stmf->policy_node)
> +               stp_policy_node_put(stmf->policy_node);
> +
> +       return ret;
> +}
> +
> +static void stm_write(struct stm_data *data, unsigned int master,
> +                     unsigned int channel, const char *buf, size_t count)
> +{
> +       unsigned int flags = STP_PACKET_TIMESTAMPED;
> +       const unsigned char *p = buf, nil = 0;
> +       size_t pos;
> +       ssize_t sz;
> +
> +       for (pos = 0, p = buf; count > pos; pos += sz, p += sz) {
> +               sz = min_t(unsigned int, count - pos, 8);
> +               sz = data->packet(data, master, channel, STP_PACKET_DATA, flags,
> +                                 sz, p);
> +               flags = 0;
> +       }
> +
> +       data->packet(data, master, channel, STP_PACKET_FLAG, 0, 0, &nil);
> +}
> +
> +static ssize_t stm_char_write(struct file *file, const char __user *buf,
> +                             size_t count, loff_t *ppos)
> +{
> +       struct stm_file *stmf = file->private_data;
> +       struct stm_device *stm = stmf->stm;
> +       char *kbuf;
> +       int err;
> +
> +       /*
> +        * if no m/c have been assigned to this writer up to this
> +        * point, use "default" policy entry
> +        */
> +       if (!stmf->output.nr_chans) {
> +               err = stm_file_assign(stmf, "default", 1);
> +               /*
> +                * EBUSY means that somebody else just assigned this
> +                * output, which is just fine for write()
> +                */
> +               if (err && err != -EBUSY)
> +                       return err;
> +       }
> +
> +       kbuf = kmalloc(count + 1, GFP_KERNEL);
> +       if (!kbuf)
> +               return -ENOMEM;
> +
> +       err = copy_from_user(kbuf, buf, count);
> +       if (err) {
> +               kfree(kbuf);
> +               return -EFAULT;
> +       }
> +
> +       stm_write(stm->data, stmf->output.master, stmf->output.channel, kbuf,
> +                 count);
> +
> +       kfree(kbuf);
> +
> +       return count;
> +}
> +
> +static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> +       struct stm_file *stmf = file->private_data;
> +       struct stm_device *stm = stmf->stm;
> +       unsigned long size, phys;
> +
> +       if (!stm->data->mmio_addr)
> +               return -EOPNOTSUPP;
> +
> +       if (vma->vm_pgoff)
> +               return -EINVAL;
> +
> +       size = vma->vm_end - vma->vm_start;
> +
> +       if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
> +               return -EINVAL;
> +
> +       phys = stm->data->mmio_addr(stm->data, stmf->output.master,
> +                                   stmf->output.channel,
> +                                   stmf->output.nr_chans);
> +
> +       if (!phys)
> +               return -EINVAL;
> +
> +       vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> +       vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
> +       vm_iomap_memory(vma, phys, size);
> +
> +       return 0;
> +}
> +
> +static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
> +{
> +       struct stm_device *stm = stmf->stm;
> +       struct stp_policy_id *id;
> +       int ret = -EINVAL;
> +       u32 size;
> +
> +       if (stmf->output.nr_chans)
> +               return -EBUSY;
> +
> +       if (copy_from_user(&size, arg, sizeof(size)))
> +               return -EFAULT;
> +
> +       if (size >= PATH_MAX + sizeof(*id))
> +               return -EINVAL;
> +
> +       /*
> +        * size + 1 to make sure the .id string at the bottom is terminated,
> +        * which is also why memdup_user() is not useful here
> +        */
> +       id = kzalloc(size + 1, GFP_KERNEL);
> +       if (!id)
> +               return -ENOMEM;
> +
> +       if (copy_from_user(id, arg, size)) {
> +               ret = -EFAULT;
> +               goto err_free;
> +       }
> +
> +       if (id->__reserved_0 || id->__reserved_1)
> +               goto err_free;
> +
> +       if (id->width < 1 ||
> +           id->width > PAGE_SIZE / stm->data->sw_mmiosz)
> +               goto err_free;
> +
> +       ret = stm_file_assign(stmf, id->id, id->width);
> +       if (ret)
> +               goto err_free;
> +
> +       ret = 0;
> +
> +       if (stm->data->link)
> +               ret = stm->data->link(stm->data, stmf->output.master,
> +                                     stmf->output.channel);
> +
> +       if (ret) {
> +               stm_output_free(stmf->stm, &stmf->output);
> +               stm_put_device(stmf->stm);
> +       }
> +
> +err_free:
> +       kfree(id);
> +
> +       return ret;
> +}
> +
> +static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
> +{
> +       struct stp_policy_id id = {
> +               .size           = sizeof(id),
> +               .master         = stmf->output.master,
> +               .channel        = stmf->output.channel,
> +               .width          = stmf->output.nr_chans,
> +               .__reserved_0   = 0,
> +               .__reserved_1   = 0,
> +       };
> +
> +       return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
> +}
> +
> +static long
> +stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> +       struct stm_file *stmf = file->private_data;
> +       struct stm_data *stm_data = stmf->stm->data;
> +       int err = -ENOTTY;
> +       u64 options;
> +
> +       switch (cmd) {
> +       case STP_POLICY_ID_SET:
> +               err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
> +               if (err)
> +                       return err;
> +
> +               return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
> +
> +       case STP_POLICY_ID_GET:
> +               return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
> +
> +       case STP_SET_OPTIONS:
> +               if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
> +                       return -EFAULT;
> +
> +               if (stm_data->set_options)
> +                       err = stm_data->set_options(stm_data,
> +                                                   stmf->output.master,
> +                                                   stmf->output.channel,
> +                                                   stmf->output.nr_chans,
> +                                                   options);
> +
> +               break;
> +       default:
> +               break;
> +       }
> +
> +       return err;
> +}
> +
> +#ifdef CONFIG_COMPAT
> +static long
> +stm_char_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> +       return stm_char_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
> +}
> +#else
> +#define stm_char_compat_ioctl  NULL
> +#endif
> +
> +static const struct file_operations stm_fops = {
> +       .open           = stm_char_open,
> +       .release        = stm_char_release,
> +       .write          = stm_char_write,
> +       .mmap           = stm_char_mmap,
> +       .unlocked_ioctl = stm_char_ioctl,
> +       .compat_ioctl   = stm_char_compat_ioctl,
> +       .llseek         = no_llseek,
> +};
> +
> +static void stm_device_release(struct device *dev)
> +{
> +       struct stm_device *stm = to_stm_device(dev);
> +
> +       kfree(stm);
> +}
> +
> +int stm_register_device(struct device *parent, struct stm_data *stm_data,
> +                       struct module *owner)
> +{
> +       struct stm_device *stm;
> +       unsigned int nmasters;
> +       int err = -ENOMEM;
> +
> +       if (!stm_core_up)
> +               return -EPROBE_DEFER;
> +
> +       if (!stm_data->packet || !stm_data->sw_nchannels)
> +               return -EINVAL;
> +
> +       nmasters = stm_data->sw_end - stm_data->sw_start;
> +       stm = kzalloc(sizeof(*stm) + nmasters * sizeof(void *), GFP_KERNEL);
> +       if (!stm)
> +               return -ENOMEM;
> +
> +       stm->major = register_chrdev(0, stm_data->name, &stm_fops);
> +       if (stm->major < 0)
> +               goto err_free;
> +
> +       device_initialize(&stm->dev);
> +       stm->dev.devt = MKDEV(stm->major, 0);
> +       stm->dev.class = &stm_class;
> +       stm->dev.parent = parent;
> +       stm->dev.release = stm_device_release;
> +
> +       err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
> +       if (err)
> +               goto err_device;
> +
> +       err = device_add(&stm->dev);
> +       if (err)
> +               goto err_device;
> +
> +       spin_lock_init(&stm->link_lock);
> +       INIT_LIST_HEAD(&stm->link_list);
> +
> +       spin_lock_init(&stm->mc_lock);
> +       mutex_init(&stm->policy_mutex);
> +       stm->sw_nmasters = nmasters;
> +       stm->owner = owner;
> +       stm->data = stm_data;
> +       stm_data->stm = stm;
> +
> +       return 0;
> +
> +err_device:
> +       put_device(&stm->dev);
> +err_free:
> +       kfree(stm);
> +
> +       return err;
> +}
> +EXPORT_SYMBOL_GPL(stm_register_device);
> +
> +static void __stm_source_link_drop(struct stm_source_device *src,
> +                                  struct stm_device *stm);
> +
> +void stm_unregister_device(struct stm_data *stm_data)
> +{
> +       struct stm_device *stm = stm_data->stm;
> +       struct stm_source_device *src, *iter;
> +       int i;
> +
> +       spin_lock(&stm->link_lock);
> +       list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
> +               __stm_source_link_drop(src, stm);
> +       }
> +       spin_unlock(&stm->link_lock);
> +
> +       synchronize_srcu(&stm_source_srcu);
> +
> +       unregister_chrdev(stm->major, stm_data->name);
> +
> +       mutex_lock(&stm->policy_mutex);
> +       if (stm->policy)
> +               stp_policy_unbind(stm->policy);
> +       mutex_unlock(&stm->policy_mutex);
> +
> +       for (i = 0; i < stm->sw_nmasters; i++)
> +               stp_master_free(stm, i);
> +
> +       device_unregister(&stm->dev);
> +       stm_data->stm = NULL;
> +}
> +EXPORT_SYMBOL_GPL(stm_unregister_device);
> +
> +/**
> + * stm_source_link_add() - connect an stm_source device to an stm device
> + * @src:       stm_source device
> + * @stm:       stm device
> + *
> + * This function establishes a link from stm_source to an stm device so that
> + * the former can send out trace data to the latter.
> + *
> + * Return:     0 on success, -errno otherwise.
> + */
> +static int stm_source_link_add(struct stm_source_device *src,
> +                              struct stm_device *stm)
> +{
> +       char *id;
> +       int err;
> +
> +       spin_lock(&stm->link_lock);
> +       spin_lock(&src->link_lock);
> +
> +       /* src->link is dereferenced under stm_source_srcu but not the list */
> +       rcu_assign_pointer(src->link, stm);
> +       list_add_tail(&src->link_entry, &stm->link_list);
> +
> +       spin_unlock(&src->link_lock);
> +       spin_unlock(&stm->link_lock);
> +
> +       id = kstrdup(src->data->name, GFP_KERNEL);
> +       if (id) {
> +               src->policy_node =
> +                       stp_policy_node_lookup(stm, id);
> +
> +               kfree(id);
> +       }
> +
> +       err = stm_output_assign(stm, src->data->nr_chans,
> +                               src->policy_node, &src->output);
> +
> +       if (src->policy_node)
> +               stp_policy_node_put(src->policy_node);
> +
> +       if (err)
> +               goto fail_detach;
> +
> +       /* this is to notify the STM device that a new link has been made */
> +       if (stm->data->link)
> +               err = stm->data->link(stm->data, src->output.master,
> +                                     src->output.channel);
> +
> +       if (err)
> +               goto fail_free_output;
> +
> +       /* this is to let the source carry out all necessary preparations */
> +       if (src->data->link)
> +               src->data->link(src->data);
> +
> +       return 0;
> +
> +fail_free_output:
> +       stm_output_free(stm, &src->output);
> +       stm_put_device(stm);
> +
> +fail_detach:
> +       spin_lock(&stm->link_lock);
> +       spin_lock(&src->link_lock);
> +
> +       rcu_assign_pointer(src->link, NULL);
> +       list_del_init(&src->link_entry);
> +
> +       spin_unlock(&src->link_lock);
> +       spin_unlock(&stm->link_lock);
> +
> +       return err;
> +}
> +
> +/**
> + * __stm_source_link_drop() - detach stm_source from an stm device
> + * @src:       stm_source device
> + * @stm:       stm device
> + *
> + * If @stm is @src::link, disconnect them from one another and put the
> + * reference on the @stm device.
> + *
> + * Caller must hold stm::link_lock.
> + */
> +static void __stm_source_link_drop(struct stm_source_device *src,
> +                                  struct stm_device *stm)
> +{
> +       spin_lock(&src->link_lock);
> +       if (WARN_ON_ONCE(src->link != stm)) {
> +               spin_unlock(&src->link_lock);
> +               return;
> +       }
> +
> +       stm_output_free(src->link, &src->output);
> +       /* caller must hold stm::link_lock */
> +       list_del_init(&src->link_entry);
> +       /* matches stm_find_device() from stm_source_link_store() */
> +       stm_put_device(src->link);
> +       rcu_assign_pointer(src->link, NULL);
> +
> +       spin_unlock(&src->link_lock);
> +}
> +
> +/**
> + * stm_source_link_drop() - detach stm_source from its stm device
> + * @src:       stm_source device
> + *
> + * Unlinking means disconnecting from source's STM device; after this
> + * writes will be unsuccessful until it is linked to a new STM device.
> + *
> + * This will happen on "stm_source_link" sysfs attribute write to undo
> + * the existing link (if any), or on linked STM device's de-registration.
> + */
> +static void stm_source_link_drop(struct stm_source_device *src)
> +{
> +       struct stm_device *stm;
> +       int idx;
> +
> +       idx = srcu_read_lock(&stm_source_srcu);
> +       stm = srcu_dereference(src->link, &stm_source_srcu);
> +
> +       if (stm) {
> +               if (src->data->unlink)
> +                       src->data->unlink(src->data);
> +
> +               spin_lock(&stm->link_lock);
> +               __stm_source_link_drop(src, stm);
> +               spin_unlock(&stm->link_lock);
> +       }
> +
> +       srcu_read_unlock(&stm_source_srcu, idx);
> +}
> +
> +static ssize_t stm_source_link_show(struct device *dev,
> +                                   struct device_attribute *attr,
> +                                   char *buf)
> +{
> +       struct stm_source_device *src = to_stm_source_device(dev);
> +       struct stm_device *stm;
> +       int idx, ret;
> +
> +       idx = srcu_read_lock(&stm_source_srcu);
> +       stm = srcu_dereference(src->link, &stm_source_srcu);
> +       ret = sprintf(buf, "%s\n",
> +                     stm ? dev_name(&stm->dev) : "<none>");
> +       srcu_read_unlock(&stm_source_srcu, idx);
> +
> +       return ret;
> +}
> +
> +static ssize_t stm_source_link_store(struct device *dev,
> +                                    struct device_attribute *attr,
> +                                    const char *buf, size_t count)
> +{
> +       struct stm_source_device *src = to_stm_source_device(dev);
> +       struct stm_device *link;
> +       int err;
> +
> +       stm_source_link_drop(src);
> +
> +       link = stm_find_device(buf);
> +       if (!link)
> +               return -EINVAL;
> +
> +       err = stm_source_link_add(src, link);
> +       if (err)
> +               stm_put_device(link);
> +
> +       return err ? : count;
> +}
> +
> +static DEVICE_ATTR_RW(stm_source_link);
> +
> +static struct attribute *stm_source_attrs[] = {
> +       &dev_attr_stm_source_link.attr,
> +       NULL,
> +};
> +
> +ATTRIBUTE_GROUPS(stm_source);
> +
> +static struct class stm_source_class = {
> +       .name           = "stm_source",
> +       .dev_groups     = stm_source_groups,
> +};
> +
> +static void stm_source_device_release(struct device *dev)
> +{
> +       struct stm_source_device *src = to_stm_source_device(dev);
> +
> +       kfree(src);
> +}
> +
> +/**
> + * stm_source_register_device() - register an stm_source device
> + * @parent:    parent device
> + * @data:      device description structure
> + *
> + * This will create a device of stm_source class that can write
> + * data to an stm device once linked.
> + *
> + * Return:     0 on success, -errno otherwise.
> + */
> +int stm_source_register_device(struct device *parent,
> +                              struct stm_source_data *data)
> +{
> +       struct stm_source_device *src;
> +       int err;
> +
> +       if (!stm_core_up)
> +               return -EPROBE_DEFER;
> +
> +       src = kzalloc(sizeof(*src), GFP_KERNEL);
> +       if (!src)
> +               return -ENOMEM;
> +
> +       device_initialize(&src->dev);
> +       src->dev.class = &stm_source_class;
> +       src->dev.parent = parent;
> +       src->dev.release = stm_source_device_release;
> +
> +       err = kobject_set_name(&src->dev.kobj, "%s", data->name);
> +       if (err)
> +               goto err;
> +
> +       err = device_add(&src->dev);
> +       if (err)
> +               goto err;
> +
> +       spin_lock_init(&src->link_lock);
> +       INIT_LIST_HEAD(&src->link_entry);
> +       src->data = data;
> +       data->src = src;
> +
> +       return 0;
> +
> +err:
> +       put_device(&src->dev);
> +       kfree(src);
> +
> +       return err;
> +}
> +EXPORT_SYMBOL_GPL(stm_source_register_device);
> +
> +/**
> + * stm_source_unregister_device() - unregister an stm_source device
> + * @data:      device description that was used to register the device
> + *
> + * This will remove a previously created stm_source device from the system.
> + */
> +void stm_source_unregister_device(struct stm_source_data *data)
> +{
> +       struct stm_source_device *src = data->src;
> +
> +       stm_source_link_drop(src);
> +
> +       device_destroy(&stm_source_class, src->dev.devt);
> +}
> +EXPORT_SYMBOL_GPL(stm_source_unregister_device);
> +
> +int stm_source_write(struct stm_source_data *data, unsigned int chan,
> +                    const char *buf, size_t count)
> +{
> +       struct stm_source_device *src = data->src;
> +       struct stm_device *stm;
> +       int idx;
> +
> +       if (!src->output.nr_chans)
> +               return -ENODEV;
> +
> +       if (chan >= src->output.nr_chans)
> +               return -EINVAL;
> +
> +       idx = srcu_read_lock(&stm_source_srcu);
> +
> +       stm = srcu_dereference(src->link, &stm_source_srcu);
> +       if (stm)
> +               stm_write(stm->data, src->output.master,
> +                         src->output.channel + chan,
> +                         buf, count);
> +       else
> +               count = -ENODEV;
> +
> +       srcu_read_unlock(&stm_source_srcu, idx);
> +
> +       return count;
> +}
> +EXPORT_SYMBOL_GPL(stm_source_write);
> +
> +static int __init stm_core_init(void)
> +{
> +       int err;
> +
> +       err = class_register(&stm_class);
> +       if (err)
> +               return err;
> +
> +       err = class_register(&stm_source_class);
> +       if (err)
> +               goto err_stm;
> +
> +       err = stp_configfs_init();
> +       if (err)
> +               goto err_src;
> +
> +       init_srcu_struct(&stm_source_srcu);
> +
> +       stm_core_up++;
> +
> +       return 0;
> +
> +err_src:
> +       class_unregister(&stm_source_class);
> +err_stm:
> +       class_unregister(&stm_class);
> +
> +       return err;
> +}
> +
> +module_init(stm_core_init);
> +
> +static void __exit stm_core_exit(void)
> +{
> +       cleanup_srcu_struct(&stm_source_srcu);
> +       class_unregister(&stm_source_class);
> +       class_unregister(&stm_class);
> +       stp_configfs_exit();
> +}
> +
> +module_exit(stm_core_exit);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("System Trace Module device class");
> +MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>");
> diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
> new file mode 100644
> index 0000000000..6498a9dbb7
> --- /dev/null
> +++ b/drivers/hwtracing/stm/policy.c
> @@ -0,0 +1,529 @@
> +/*
> + * System Trace Module (STM) master/channel allocation policy management
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * A master/channel allocation policy allows mapping string identifiers to
> + * master and channel ranges, where allocation can be done.
> + */
> +
> +#define pr_fmt(fmt)    KBUILD_MODNAME ": " fmt
> +
> +#include <linux/types.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/configfs.h>
> +#include <linux/slab.h>
> +#include <linux/stm.h>
> +#include "stm.h"
> +
> +/*
> + * STP Master/Channel allocation policy configfs layout.
> + */
> +
> +struct stp_policy {
> +       struct config_group     group;
> +       struct stm_device       *stm;
> +};
> +
> +struct stp_policy_node {
> +       struct config_group     group;
> +       struct stp_policy       *policy;
> +       unsigned int            first_master;
> +       unsigned int            last_master;
> +       unsigned int            first_channel;
> +       unsigned int            last_channel;
> +};
> +
> +static struct configfs_subsystem stp_policy_subsys;
> +
> +void stp_policy_node_get_ranges(struct stp_policy_node *policy_node,
> +                               unsigned int *mstart, unsigned int *mend,
> +                               unsigned int *cstart, unsigned int *cend)
> +{
> +       *mstart = policy_node->first_master;
> +       *mend   = policy_node->last_master;
> +       *cstart = policy_node->first_channel;
> +       *cend   = policy_node->last_channel;
> +}
> +
> +static inline char *stp_policy_node_name(struct stp_policy_node *policy_node)
> +{
> +       return policy_node->group.cg_item.ci_name ? : "<none>";
> +}
> +
> +static inline struct stp_policy *to_stp_policy(struct config_item *item)
> +{
> +       return item ?
> +               container_of(to_config_group(item), struct stp_policy, group) :
> +               NULL;
> +}
> +
> +static inline struct stp_policy_node *
> +to_stp_policy_node(struct config_item *item)
> +{
> +       return item ?
> +               container_of(to_config_group(item), struct stp_policy_node,
> +                            group) :
> +               NULL;
> +}
> +
> +static ssize_t stp_policy_node_masters_show(struct stp_policy_node *policy_node,
> +                                           char *page)
> +{
> +       ssize_t count;
> +
> +       count = sprintf(page, "%u %u\n", policy_node->first_master,
> +                       policy_node->last_master);
> +
> +       return count;
> +}
> +
> +static ssize_t
> +stp_policy_node_masters_store(struct stp_policy_node *policy_node,
> +                             const char *page, size_t count)
> +{
> +       unsigned int first, last;
> +       struct stm_device *stm;
> +       char *p = (char *)page;
> +       ssize_t ret = -ENODEV;
> +
> +       if (sscanf(p, "%u %u", &first, &last) != 2)
> +               return -EINVAL;
> +
> +       mutex_lock(&stp_policy_subsys.su_mutex);
> +       stm = policy_node->policy->stm;
> +       if (!stm)
> +               goto unlock;
> +
> +       /* must be within [sw_start..sw_end], which is an inclusive range */
> +       if (first > INT_MAX || last > INT_MAX || first > last ||
> +           first < stm->data->sw_start ||
> +           last > stm->data->sw_end) {
> +               ret = -ERANGE;
> +               goto unlock;
> +       }
> +
> +       ret = count;
> +       policy_node->first_master = first;
> +       policy_node->last_master = last;
> +
> +unlock:
> +       mutex_unlock(&stp_policy_subsys.su_mutex);
> +
> +       return ret;
> +}
> +
> +static ssize_t
> +stp_policy_node_channels_show(struct stp_policy_node *policy_node, char *page)
> +{
> +       ssize_t count;
> +
> +       count = sprintf(page, "%u %u\n", policy_node->first_channel,
> +                       policy_node->last_channel);
> +
> +       return count;
> +}
> +
> +static ssize_t
> +stp_policy_node_channels_store(struct stp_policy_node *policy_node,
> +                              const char *page, size_t count)
> +{
> +       unsigned int first, last;
> +       struct stm_device *stm;
> +       char *p = (char *)page;
> +       ssize_t ret = -ENODEV;
> +
> +       if (sscanf(p, "%u %u", &first, &last) != 2)
> +               return -EINVAL;
> +
> +       mutex_lock(&stp_policy_subsys.su_mutex);
> +       stm = policy_node->policy->stm;
> +       if (!stm)
> +               goto unlock;
> +
> +       if (first > INT_MAX || last > INT_MAX || first > last ||
> +           last >= stm->data->sw_nchannels) {
> +               ret = -ERANGE;
> +               goto unlock;
> +       }
> +
> +       ret = count;
> +       policy_node->first_channel = first;
> +       policy_node->last_channel = last;
> +
> +unlock:
> +       mutex_unlock(&stp_policy_subsys.su_mutex);
> +
> +       return ret;
> +}
> +
> +static void stp_policy_node_release(struct config_item *item)
> +{
> +       kfree(to_stp_policy_node(item));
> +}
> +
> +struct stp_policy_node_attribute {
> +       struct configfs_attribute       attr;
> +       ssize_t (*show)(struct stp_policy_node *, char *);
> +       ssize_t (*store)(struct stp_policy_node *, const char *, size_t);
> +};
> +
> +static ssize_t stp_policy_node_attr_show(struct config_item *item,
> +                                        struct configfs_attribute *attr,
> +                                        char *page)
> +{
> +       struct stp_policy_node *policy_node = to_stp_policy_node(item);
> +       struct stp_policy_node_attribute *pn_attr =
> +               container_of(attr, struct stp_policy_node_attribute, attr);
> +       ssize_t count = 0;
> +
> +       if (pn_attr->show)
> +               count = pn_attr->show(policy_node, page);
> +
> +       return count;
> +}
> +
> +static ssize_t stp_policy_node_attr_store(struct config_item *item,
> +                                         struct configfs_attribute *attr,
> +                                         const char *page, size_t len)
> +{
> +       struct stp_policy_node *policy_node = to_stp_policy_node(item);
> +       struct stp_policy_node_attribute *pn_attr =
> +               container_of(attr, struct stp_policy_node_attribute, attr);
> +       ssize_t count = -EINVAL;
> +
> +       if (pn_attr->store)
> +               count = pn_attr->store(policy_node, page, len);
> +
> +       return count;
> +}
> +
> +static struct configfs_item_operations stp_policy_node_item_ops = {
> +       .release                = stp_policy_node_release,
> +       .show_attribute         = stp_policy_node_attr_show,
> +       .store_attribute        = stp_policy_node_attr_store,
> +};
> +
> +static struct stp_policy_node_attribute stp_policy_node_attr_range = {
> +       .attr   = {
> +               .ca_owner = THIS_MODULE,
> +               .ca_name = "masters",
> +               .ca_mode = S_IRUGO | S_IWUSR,
> +       },
> +       .show   = stp_policy_node_masters_show,
> +       .store  = stp_policy_node_masters_store,
> +};
> +
> +static struct stp_policy_node_attribute stp_policy_node_attr_channels = {
> +       .attr   = {
> +               .ca_owner = THIS_MODULE,
> +               .ca_name = "channels",
> +               .ca_mode = S_IRUGO | S_IWUSR,
> +       },
> +       .show   = stp_policy_node_channels_show,
> +       .store  = stp_policy_node_channels_store,
> +};
> +
> +static struct configfs_attribute *stp_policy_node_attrs[] = {
> +       &stp_policy_node_attr_range.attr,
> +       &stp_policy_node_attr_channels.attr,
> +       NULL,
> +};
> +
> +static struct config_item_type stp_policy_type;
> +static struct config_item_type stp_policy_node_type;
> +
> +static struct config_group *
> +stp_policy_node_make(struct config_group *group, const char *name)
> +{
> +       struct stp_policy_node *policy_node, *parent_node;
> +       struct stp_policy *policy;
> +
> +       if (group->cg_item.ci_type == &stp_policy_type) {
> +               policy = container_of(group, struct stp_policy, group);
> +       } else {
> +               parent_node = container_of(group, struct stp_policy_node,
> +                                          group);
> +               policy = parent_node->policy;
> +       }
> +
> +       if (!policy->stm)
> +               return ERR_PTR(-ENODEV);
> +
> +       policy_node = kzalloc(sizeof(struct stp_policy_node), GFP_KERNEL);
> +       if (!policy_node)
> +               return ERR_PTR(-ENOMEM);
> +
> +       config_group_init_type_name(&policy_node->group, name,
> +                                   &stp_policy_node_type);
> +
> +       policy_node->policy = policy;
> +
> +       /* default values for the attributes */
> +       policy_node->first_master = policy->stm->data->sw_start;
> +       policy_node->last_master = policy->stm->data->sw_end;
> +       policy_node->first_channel = 0;
> +       policy_node->last_channel = policy->stm->data->sw_nchannels - 1;
> +
> +       return &policy_node->group;
> +}
> +
> +static void
> +stp_policy_node_drop(struct config_group *group, struct config_item *item)
> +{
> +       config_item_put(item);
> +}
> +
> +static struct configfs_group_operations stp_policy_node_group_ops = {
> +       .make_group     = stp_policy_node_make,
> +       .drop_item      = stp_policy_node_drop,
> +};
> +
> +static struct config_item_type stp_policy_node_type = {
> +       .ct_item_ops    = &stp_policy_node_item_ops,
> +       .ct_group_ops   = &stp_policy_node_group_ops,
> +       .ct_attrs       = stp_policy_node_attrs,
> +       .ct_owner       = THIS_MODULE,
> +};
> +
> +/*
> + * Root group: policies.
> + */
> +static struct configfs_attribute stp_policy_attr_device = {
> +       .ca_owner = THIS_MODULE,
> +       .ca_name = "device",
> +       .ca_mode = S_IRUGO,
> +};
> +
> +static struct configfs_attribute *stp_policy_attrs[] = {
> +       &stp_policy_attr_device,
> +       NULL,
> +};
> +
> +static ssize_t stp_policy_attr_show(struct config_item *item,
> +                                   struct configfs_attribute *attr,
> +                                   char *page)
> +{
> +       struct stp_policy *policy = to_stp_policy(item);
> +       ssize_t count;
> +
> +       count = sprintf(page, "%s\n",
> +                       (policy && policy->stm) ?
> +                       policy->stm->data->name :
> +                       "<none>");
> +
> +       return count;
> +}
> +
> +void stp_policy_unbind(struct stp_policy *policy)
> +{
> +       struct stm_device *stm = policy->stm;
> +
> +       if (WARN_ON_ONCE(!policy->stm))
> +               return;
> +
> +       mutex_lock(&stm->policy_mutex);
> +       stm->policy = NULL;
> +       mutex_unlock(&stm->policy_mutex);
> +
> +       policy->stm = NULL;
> +
> +       stm_put_device(stm);
> +}
> +
> +static void stp_policy_release(struct config_item *item)
> +{
> +       struct stp_policy *policy = to_stp_policy(item);
> +
> +       stp_policy_unbind(policy);
> +       kfree(policy);
> +}
> +
> +static struct configfs_item_operations stp_policy_item_ops = {
> +       .release                = stp_policy_release,
> +       .show_attribute         = stp_policy_attr_show,
> +};
> +
> +static struct configfs_group_operations stp_policy_group_ops = {
> +       .make_group     = stp_policy_node_make,
> +};
> +
> +static struct config_item_type stp_policy_type = {
> +       .ct_item_ops    = &stp_policy_item_ops,
> +       .ct_group_ops   = &stp_policy_group_ops,
> +       .ct_attrs       = stp_policy_attrs,
> +       .ct_owner       = THIS_MODULE,
> +};
> +
> +static struct config_group *
> +stp_policies_make(struct config_group *group, const char *name)
> +{
> +       struct config_group *ret;
> +       struct stm_device *stm;
> +       char *devname, *p;
> +
> +       devname = kasprintf(GFP_KERNEL, "%s", name);
> +       if (!devname)
> +               return ERR_PTR(-ENOMEM);
> +
> +       /*
> +        * node must look like <device_name>.<policy_name>, where
> +        * <device_name> is the name of an existing stm device and
> +        * <policy_name> is an arbitrary string
> +        */
> +       p = strchr(devname, '.');
> +       if (!p) {
> +               kfree(devname);
> +               return ERR_PTR(-EINVAL);
> +       }
> +
> +       *p++ = '\0';
> +
> +       stm = stm_find_device(devname);
> +       kfree(devname);
> +
> +       if (!stm)
> +               return ERR_PTR(-ENODEV);
> +
> +       mutex_lock(&stm->policy_mutex);
> +       if (stm->policy) {
> +               ret = ERR_PTR(-EBUSY);
> +               goto unlock_policy;
> +       }
> +
> +       stm->policy = kzalloc(sizeof(*stm->policy), GFP_KERNEL);
> +       if (!stm->policy) {
> +               ret = ERR_PTR(-ENOMEM);
> +               goto unlock_policy;
> +       }
> +
> +       config_group_init_type_name(&stm->policy->group, name,
> +                                   &stp_policy_type);
> +       stm->policy->stm = stm;
> +
> +       ret = &stm->policy->group;
> +
> +unlock_policy:
> +       mutex_unlock(&stm->policy_mutex);
> +
> +       if (IS_ERR(ret))
> +               stm_put_device(stm);
> +
> +       return ret;
> +}
> +
> +static struct configfs_group_operations stp_policies_group_ops = {
> +       .make_group     = stp_policies_make,
> +};
> +
> +static struct config_item_type stp_policies_type = {
> +       .ct_group_ops   = &stp_policies_group_ops,
> +       .ct_owner       = THIS_MODULE,
> +};
> +
> +static struct configfs_subsystem stp_policy_subsys = {
> +       .su_group = {
> +               .cg_item = {
> +                       .ci_namebuf     = "stp-policy",
> +                       .ci_type        = &stp_policies_type,
> +               },
> +       },
> +};
> +
> +/*
> + * Lock the policy mutex from the outside
> + */
> +static struct stp_policy_node *
> +__stp_policy_node_lookup(struct stp_policy *policy, char *s)
> +{
> +       struct stp_policy_node *policy_node, *ret;
> +       struct list_head *head = &policy->group.cg_children;
> +       struct config_item *item;
> +       char *start, *end = s;
> +
> +       if (list_empty(head))
> +               return NULL;
> +
> +       /* return the first entry if everything else fails */
> +       item = list_entry(head->next, struct config_item, ci_entry);
> +       ret = to_stp_policy_node(item);
> +
> +next:
> +       for (;;) {
> +               start = strsep(&end, "/");
> +               if (!start)
> +                       break;
> +
> +               if (!*start)
> +                       continue;
> +
> +               list_for_each_entry(item, head, ci_entry) {
> +                       policy_node = to_stp_policy_node(item);
> +
> +                       if (!strcmp(start,
> +                                   policy_node->group.cg_item.ci_name)) {
> +                               ret = policy_node;
> +
> +                               if (!end)
> +                                       goto out;
> +
> +                               head = &policy_node->group.cg_children;
> +                               goto next;
> +                       }
> +               }
> +               break;
> +       }
> +
> +out:
> +       return ret;
> +}
> +
> +
> +struct stp_policy_node *
> +stp_policy_node_lookup(struct stm_device *stm, char *s)
> +{
> +       struct stp_policy_node *policy_node = NULL;
> +
> +       mutex_lock(&stp_policy_subsys.su_mutex);
> +
> +       mutex_lock(&stm->policy_mutex);
> +       if (stm->policy)
> +               policy_node = __stp_policy_node_lookup(stm->policy, s);
> +       mutex_unlock(&stm->policy_mutex);
> +
> +       if (policy_node)
> +               config_item_get(&policy_node->group.cg_item);
> +       mutex_unlock(&stp_policy_subsys.su_mutex);
> +
> +       return policy_node;
> +}
> +
> +void stp_policy_node_put(struct stp_policy_node *policy_node)
> +{
> +       config_item_put(&policy_node->group.cg_item);
> +}
> +
> +int __init stp_configfs_init(void)
> +{
> +       int err;
> +
> +       config_group_init(&stp_policy_subsys.su_group);
> +       mutex_init(&stp_policy_subsys.su_mutex);
> +       err = configfs_register_subsystem(&stp_policy_subsys);
> +
> +       return err;
> +}
> +
> +void __exit stp_configfs_exit(void)
> +{
> +       configfs_unregister_subsystem(&stp_policy_subsys);
> +}
> diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h
> new file mode 100644
> index 0000000000..cf33bf976a
> --- /dev/null
> +++ b/drivers/hwtracing/stm/stm.h
> @@ -0,0 +1,87 @@
> +/*
> + * System Trace Module (STM) infrastructure
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * STM class implements generic infrastructure for  System Trace Module devices
> + * as defined in MIPI STPv2 specification.
> + */
> +
> +#ifndef _STM_STM_H_
> +#define _STM_STM_H_
> +
> +struct stp_policy;
> +struct stp_policy_node;
> +
> +struct stp_policy_node *
> +stp_policy_node_lookup(struct stm_device *stm, char *s);
> +void stp_policy_node_put(struct stp_policy_node *policy_node);
> +void stp_policy_unbind(struct stp_policy *policy);
> +
> +void stp_policy_node_get_ranges(struct stp_policy_node *policy_node,
> +                               unsigned int *mstart, unsigned int *mend,
> +                               unsigned int *cstart, unsigned int *cend);
> +int stp_configfs_init(void);
> +void stp_configfs_exit(void);
> +
> +struct stp_master {
> +       unsigned int    nr_free;
> +       unsigned long   chan_map[0];
> +};
> +
> +struct stm_device {
> +       struct device           dev;
> +       struct module           *owner;
> +       struct stp_policy       *policy;
> +       struct mutex            policy_mutex;
> +       int                     major;
> +       unsigned int            sw_nmasters;
> +       struct stm_data         *data;
> +       spinlock_t              link_lock;
> +       struct list_head        link_list;
> +       /* master allocation */
> +       spinlock_t              mc_lock;
> +       struct stp_master       *masters[0];
> +};
> +
> +#define to_stm_device(_d)                              \
> +       container_of((_d), struct stm_device, dev)
> +
> +struct stm_output {
> +       unsigned int            master;
> +       unsigned int            channel;
> +       unsigned int            nr_chans;
> +};
> +
> +struct stm_file {
> +       struct stm_device       *stm;
> +       struct stp_policy_node  *policy_node;
> +       struct stm_output       output;
> +};
> +
> +struct stm_device *stm_find_device(const char *name);
> +void stm_put_device(struct stm_device *stm);
> +
> +struct stm_source_device {
> +       struct device           dev;
> +       struct stm_source_data  *data;
> +       spinlock_t              link_lock;
> +       struct stm_device       *link;
> +       struct list_head        link_entry;
> +       /* one output per stm_source device */
> +       struct stp_policy_node  *policy_node;
> +       struct stm_output       output;
> +};
> +
> +#define to_stm_source_device(_d)                               \
> +       container_of((_d), struct stm_source_device, dev)
> +
> +#endif /* _STM_STM_H_ */
> diff --git a/include/linux/stm.h b/include/linux/stm.h
> new file mode 100644
> index 0000000000..9d0083d364
> --- /dev/null
> +++ b/include/linux/stm.h
> @@ -0,0 +1,126 @@
> +/*
> + * System Trace Module (STM) infrastructure apis
> + * Copyright (C) 2014 Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + */
> +
> +#ifndef _STM_H_
> +#define _STM_H_
> +
> +#include <linux/device.h>
> +
> +/**
> + * enum stp_packet_type - STP packets that an STM driver sends
> + */
> +enum stp_packet_type {
> +       STP_PACKET_DATA = 0,
> +       STP_PACKET_FLAG,
> +       STP_PACKET_USER,
> +       STP_PACKET_MERR,
> +       STP_PACKET_GERR,
> +       STP_PACKET_TRIG,
> +       STP_PACKET_XSYNC,
> +};
> +
> +/**
> + * enum stp_packet_flags - STP packet modifiers
> + */
> +enum stp_packet_flags {
> +       STP_PACKET_MARKED       = 0x1,
> +       STP_PACKET_TIMESTAMPED  = 0x2,
> +};
> +
> +struct stp_policy;
> +
> +struct stm_device;
> +
> +/**
> + * struct stm_data - STM device description and callbacks
> + * @name:              device name
> + * @stm:               internal structure, only used by stm class code
> + * @sw_start:          first STP master available to software
> + * @sw_end:            last STP master available to software
> + * @sw_nchannels:      number of STP channels per master
> + * @sw_mmiosz:         size of one channel's IO space, for mmap, optional
> + * @packet:            callback that sends an STP packet
> + * @mmio_addr:         mmap callback, optional
> + * @link:              called when a new stm_source gets linked to us, optional
> + * @unlink:            likewise for unlinking, again optional
> + * @set_options:       set device-specific options on a channel
> + *
> + * Fill out this structure before calling stm_register_device() to create
> + * an STM device and stm_unregister_device() to destroy it. It will also be
> + * passed back to @packet(), @mmio_addr(), @link(), @unlink() and @set_options()
> + * callbacks.
> + *
> + * Normally, an STM device will have a range of masters available to software
> + * and the rest being statically assigned to various hardware trace sources.
> + * The former is defined by the the range [@sw_start..@sw_end] of the device
> + * description. That is, the lowest master that can be allocated to software
> + * writers is @sw_start and data from this writer will appear is @sw_start
> + * master in the STP stream.
> + */
> +struct stm_data {
> +       const char              *name;
> +       struct stm_device       *stm;
> +       unsigned int            sw_start;
> +       unsigned int            sw_end;
> +       unsigned int            sw_nchannels;
> +       unsigned int            sw_mmiosz;
> +       ssize_t                 (*packet)(struct stm_data *, unsigned int,
> +                                         unsigned int, unsigned int,
> +                                         unsigned int, unsigned int,
> +                                         const unsigned char *);
> +       phys_addr_t             (*mmio_addr)(struct stm_data *, unsigned int,
> +                                            unsigned int, unsigned int);
> +       int                     (*link)(struct stm_data *, unsigned int,
> +                                       unsigned int);
> +       void                    (*unlink)(struct stm_data *, unsigned int,
> +                                         unsigned int);
> +       long                    (*set_options)(struct stm_data *, unsigned int,
> +                                              unsigned int, unsigned int,
> +                                              unsigned long);
> +};
> +
> +int stm_register_device(struct device *parent, struct stm_data *stm_data,
> +                       struct module *owner);
> +void stm_unregister_device(struct stm_data *stm_data);
> +
> +struct stm_source_device;
> +
> +/**
> + * struct stm_source_data - STM source device description and callbacks
> + * @name:      device name, will be used for policy lookup
> + * @src:       internal structure, only used by stm class code
> + * @nr_chans:  number of channels to allocate
> + * @link:      called when this source gets linked to an STM device
> + * @unlink:    called when this source is about to get unlinked from its STM
> + *
> + * Fill in this structure before calling stm_source_register_device() to
> + * register a source device. Also pass it to unregister and write calls.
> + */
> +struct stm_source_data {
> +       const char              *name;
> +       struct stm_source_device *src;
> +       unsigned int            percpu;
> +       unsigned int            nr_chans;
> +       int                     (*link)(struct stm_source_data *data);
> +       void                    (*unlink)(struct stm_source_data *data);
> +};
> +
> +int stm_source_register_device(struct device *parent,
> +                              struct stm_source_data *data);
> +void stm_source_unregister_device(struct stm_source_data *data);
> +
> +int stm_source_write(struct stm_source_data *data, unsigned int chan,
> +                    const char *buf, size_t count);
> +
> +#endif /* _STM_H_ */
> diff --git a/include/uapi/linux/stm.h b/include/uapi/linux/stm.h
> new file mode 100644
> index 0000000000..626a8d3f63
> --- /dev/null
> +++ b/include/uapi/linux/stm.h
> @@ -0,0 +1,50 @@
> +/*
> + * System Trace Module (STM) userspace interfaces
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * STM class implements generic infrastructure for  System Trace Module devices
> + * as defined in MIPI STPv2 specification.
> + */
> +
> +#ifndef _UAPI_LINUX_STM_H
> +#define _UAPI_LINUX_STM_H
> +
> +#include <linux/types.h>
> +
> +/**
> + * struct stp_policy_id - identification for the STP policy
> + * @size:      size of the structure including real id[] length
> + * @master:    assigned master
> + * @channel:   first assigned channel
> + * @width:     number of requested channels
> + * @id:                identification string
> + *
> + * User must calculate the total size of the structure and put it into
> + * @size field, fill out the @id and desired @width. In return, kernel
> + * fills out @master, @channel and @width.
> + */
> +struct stp_policy_id {
> +       __u32           size;
> +       __u16           master;
> +       __u16           channel;
> +       __u16           width;
> +       /* padding */
> +       __u16           __reserved_0;
> +       __u32           __reserved_1;
> +       char            id[0];
> +};
> +
> +#define STP_POLICY_ID_SET      _IOWR('%', 0, struct stp_policy_id)
> +#define STP_POLICY_ID_GET      _IOR('%', 1, struct stp_policy_id)
> +#define STP_SET_OPTIONS                _IOW('%', 2, __u64)
> +
> +#endif /* _UAPI_LINUX_STM_H */
> --
> 2.1.4
>

Reviewed-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
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