Re: [PATCH v7 2/3] uacce: add uacce driver

From: Jonathan Cameron
Date: Mon Nov 11 2019 - 06:19:44 EST

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On Tue, 5 Nov 2019 15:43:31 +0800
zhangfei <zhangfei.gao@xxxxxxxxxx> wrote:

> Hi, Jonathan
>
> Thanks for the suggestions
>
> On 2019/11/1 äå1:13, Jonathan Cameron wrote:
> > On Tue, 29 Oct 2019 14:40:15 +0800
> > Zhangfei Gao <zhangfei.gao@xxxxxxxxxx> wrote:
> >
> >> From: Kenneth Lee <liguozhu@xxxxxxxxxxxxx>
> >>
> >> Uacce (Unified/User-space-access-intended Accelerator Framework) targets to
> >> provide Shared Virtual Addressing (SVA) between accelerators and processes.
> >> So accelerator can access any data structure of the main cpu.
> >> This differs from the data sharing between cpu and io device, which share
> >> data content rather than address.
> >> Since unified address, hardware and user space of process can share the
> >> same virtual address in the communication.
> >>
> >> Uacce create a chrdev for every registration, the queue is allocated to
> >> the process when the chrdev is opened. Then the process can access the
> >> hardware resource by interact with the queue file. By mmap the queue
> >> file space to user space, the process can directly put requests to the
> >> hardware without syscall to the kernel space.
> >>
> >> Signed-off-by: Kenneth Lee <liguozhu@xxxxxxxxxxxxx>
> >> Signed-off-by: Zaibo Xu <xuzaibo@xxxxxxxxxx>
> >> Signed-off-by: Zhou Wang <wangzhou1@xxxxxxxxxxxxx>
> >> Signed-off-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
> > Great, much more compact.
> >
> > I've not gone through this in detail yet but a few initial comments inline.
> >
> > Thanks,
> >
> > Jonathan
> >
> >> ---
> >> Documentation/ABI/testing/sysfs-driver-uacce | 53 +++
> >> drivers/misc/Kconfig | 1 +
> >> drivers/misc/Makefile | 1 +
> >> drivers/misc/uacce/Kconfig | 13 +
> >> drivers/misc/uacce/Makefile | 2 +
> >> drivers/misc/uacce/uacce.c | 574 +++++++++++++++++++++++++++
> >> include/linux/uacce.h | 163 ++++++++
> >> include/uapi/misc/uacce/uacce.h | 38 ++
> >> 8 files changed, 845 insertions(+)
> >> create mode 100644 Documentation/ABI/testing/sysfs-driver-uacce
> >> create mode 100644 drivers/misc/uacce/Kconfig
> >> create mode 100644 drivers/misc/uacce/Makefile
> >> create mode 100644 drivers/misc/uacce/uacce.c
> >> create mode 100644 include/linux/uacce.h
> >> create mode 100644 include/uapi/misc/uacce/uacce.h
> >>
> >> diff --git a/Documentation/ABI/testing/sysfs-driver-uacce b/Documentation/ABI/testing/sysfs-driver-uacce
> >> new file mode 100644
> >> index 0000000..35699dc
> >> --- /dev/null
> >> +++ b/Documentation/ABI/testing/sysfs-driver-uacce
> >> @@ -0,0 +1,53 @@
> >> +What: /sys/class/uacce/<dev_name>/id
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Id of the device.
> >> +
> >> +What: /sys/class/uacce/<dev_name>/api
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Api of the device, used by application to match the correct driver
> >> +
> >> +What: /sys/class/uacce/<dev_name>/flags
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Attributes of the device, see UACCE_DEV_xxx flag defined in uacce.h
> >> +
> >> +What: /sys/class/uacce/<dev_name>/available_instances
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Available instances left of the device
> >> +
> >> +What: /sys/class/uacce/<dev_name>/algorithms
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Algorithms supported by this accelerator
> > How are they separated? Userspace code needs to know that.
> > (comma, tab, newline?)
> Yes, will add "separated by new line"
> >
> >> +
> >> +What: /sys/class/uacce/<dev_name>/qfrt_mmio_size
> > qfrt is not the most obvious naming ever. Do we care beyond its
> > a region for this interface? region_mmio_size maybe?
> OK,
> >
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Page size of mmio region queue file
> > Size of page in this region, or number of pages in the region?
> Change to "Page numbers of mmio region queue file"

Number of pages used by queue in mmio region?

> >
> >> +
> >> +What: /sys/class/uacce/<dev_name>/qfrt_dus_size
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Page size of dus region queue file
> >> +
> >> +What: /sys/class/uacce/<dev_name>/numa_distance
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Distance of device node to cpu node
> > I wonder if we should be doing this in here. There are other standard
> > ways of obtaining this for the device. Follow parent and check node_id
> > there then use the /sys/bus/node path to find out the distances.
> Could you clarify more about this method.
> The purpose here is cpu searching the nearest device(zip) doing work.
> Does user application know which node it is running and compare distance?

Exactly. The parent device will typically be a pci device. The parent
link will point somewhere like

/sys/bus/pci/devices/000:00:10.0/

Under that directory is a numa_node file which will give you which node
the device is assigned to.

Using that number (N) read

/sys/bus/node/devices/nodeN/distance

Which should be the same as what you have from this interface.
It also provides access to info on latency and bandwidth etc
if HMAT is provided - so more info to make a decision than your
new interface here provides.

> >> +
> >> +What: /sys/class/uacce/<dev_name>/node_id
> >> +Date: Oct 2019
> >> +KernelVersion: 5.5
> >> +Contact: linux-accelerators@xxxxxxxxxxxxxxxx
> >> +Description: Id of the numa node
> >> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> >> index c55b637..929feb0 100644
> >> --- a/drivers/misc/Kconfig
> >> +++ b/drivers/misc/Kconfig
> >> @@ -481,4 +481,5 @@ source "drivers/misc/cxl/Kconfig"
> >> source "drivers/misc/ocxl/Kconfig"
> >> source "drivers/misc/cardreader/Kconfig"
> >> source "drivers/misc/habanalabs/Kconfig"
> >> +source "drivers/misc/uacce/Kconfig"
> >> endmenu
> >> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> >> index c1860d3..9abf292 100644
> >> --- a/drivers/misc/Makefile
> >> +++ b/drivers/misc/Makefile
> >> @@ -56,4 +56,5 @@ obj-$(CONFIG_OCXL) += ocxl/
> >> obj-y += cardreader/
> >> obj-$(CONFIG_PVPANIC) += pvpanic.o
> >> obj-$(CONFIG_HABANA_AI) += habanalabs/
> >> +obj-$(CONFIG_UACCE) += uacce/
> >> obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o
> >> diff --git a/drivers/misc/uacce/Kconfig b/drivers/misc/uacce/Kconfig
> >> new file mode 100644
> >> index 0000000..5e39b60
> >> --- /dev/null
> >> +++ b/drivers/misc/uacce/Kconfig
> >> @@ -0,0 +1,13 @@
> >> +config UACCE
> >> + tristate "Accelerator Framework for User Land"
> >> + depends on IOMMU_API
> >> + help
> >> + UACCE provides interface for the user process to access the hardware
> >> + without interaction with the kernel space in data path.
> >> +
> >> + The user-space interface is described in
> >> + include/uapi/misc/uacce/uacce.h
> >> +
> >> + See Documentation/misc-devices/uacce.rst for more details.
> >> +
> >> + If you don't know what to do here, say N.
> > Pessimist :) Everyone should want uacce so don't put them off. Having said
> > that perhaps for now it should be hidden and enabled on a driver by driver
> > basis?
> >
> >> diff --git a/drivers/misc/uacce/Makefile b/drivers/misc/uacce/Makefile
> >> new file mode 100644
> >> index 0000000..5b4374e
> >> --- /dev/null
> >> +++ b/drivers/misc/uacce/Makefile
> >> @@ -0,0 +1,2 @@
> >> +# SPDX-License-Identifier: GPL-2.0-or-later
> >> +obj-$(CONFIG_UACCE) += uacce.o
> >> diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
> >> new file mode 100644
> >> index 0000000..2b6b038
> >> --- /dev/null
> >> +++ b/drivers/misc/uacce/uacce.c
> >> @@ -0,0 +1,574 @@
> >> +// SPDX-License-Identifier: GPL-2.0-or-later
> >> +#include <linux/compat.h>
> >> +#include <linux/dma-iommu.h>
> >> +#include <linux/module.h>
> >> +#include <linux/poll.h>
> >> +#include <linux/uacce.h>
> >> +
> >> +static struct class *uacce_class;
> >> +static dev_t uacce_devt;
> >> +static DEFINE_MUTEX(uacce_mutex);
> >> +static DEFINE_XARRAY_ALLOC(uacce_xa);
> >> +
> >> +static int uacce_start_queue(struct uacce_queue *q)
> >> +{
> >> + int ret = -EINVAL;
> >> +
> >> + mutex_lock(&uacce_mutex);
> >> +
> >> + if (q->state != UACCE_Q_INIT)
> >> + goto out_with_lock;
> >> +
> >> + if (q->uacce->ops->start_queue) {
> >> + ret = q->uacce->ops->start_queue(q);
> >> + if (ret < 0)
> >> + goto out_with_lock;
> >> + }
> >> +
> >> + q->state = UACCE_Q_STARTED;
> > out_with_lock:
> >> + mutex_unlock(&uacce_mutex);
> >> +
> > return ret;
> > Though need to handle ret a bit differently above...
> OK
> >
> > +static int uacce_fops_mmap(struct file *filep, struct vm_area_struct *vma)
> > +{
> > + struct uacce_queue *q = filep->private_data;
> > + struct uacce_device *uacce = q->uacce;
> > + struct uacce_qfile_region *qfr;
> > + enum uacce_qfrt type = 0;
> > + unsigned int flags = 0;
> > + int ret;
> > +
> > + if (vma->vm_pgoff < UACCE_QFRT_MAX)
> > + type = vma->vm_pgoff;
> > +
> > + vma->vm_flags |= VM_DONTCOPY | VM_DONTEXPAND | VM_WIPEONFORK;
> > + vma->vm_ops = &uacce_vm_ops;
> > + vma->vm_private_data = q;
> > +
> > + mutex_lock(&uacce_mutex);
> > +
> > + if (q->qfrs[type]) {
> > + ret = -EEXIST;
> > + goto out_with_lock;
> > + }
> > +
> > + switch (type) {
> > + case UACCE_QFRT_MMIO:
> > + flags = UACCE_QFRF_SELFMT;
> > + break;
> > +
> > + case UACCE_QFRT_DUS:
> > + if (uacce->flags & UACCE_DEV_SVA) {
> > + flags = UACCE_QFRF_SELFMT;
> > + break;
> > + }
> > + break;
> > +
> > + default:
> > + WARN_ON(&uacce->dev);
> > + break;
> > + }
> > +
> > + qfr = uacce_create_region(q, vma, type, flags);
> > + if (IS_ERR(qfr)) {
> > + ret = PTR_ERR(qfr);
> > + goto out_with_lock;
> > + }
> > + q->qfrs[type] = qfr;
> > +
> > Could put
> > out_with_lock:
> > here and return ret instead of 0.
> > You'll need to set ret to default to 0 in that
> > case though.
> OK
> >
> > +static ssize_t algorithms_show(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + struct uacce_device *uacce = to_uacce_device(dev);
> > +
> > + return sprintf(buf, "%s", uacce->algs);
> > Any risk algs won't have the \n?
> > I'd kind of expect it to be a null termated arrays to allow the core
> > to format it however it wants to.
> Yes, adding \n is better.

This may then add a bonus new line if you have multiple lines already in
the string. Probably doesn't do much harm, but it's not ideal.

> >
> >> +}
> >> +
> >> +static ssize_t qfrt_mmio_size_show(struct device *dev,
> >> + struct device_attribute *attr, char *buf)
> >> +{
> >> + struct uacce_device *uacce = to_uacce_device(dev);
> >> +
> >> + return sprintf(buf, "%lu\n",
> >> + uacce->qf_pg_size[UACCE_QFRT_MMIO] << PAGE_SHIFT);
> >> +}
> >> +
> >> +static ssize_t qfrt_dus_size_show(struct device *dev,
> >> + struct device_attribute *attr, char *buf)
> >> +{
> >> + struct uacce_device *uacce = to_uacce_device(dev);
> >> +
> >> + return sprintf(buf, "%lu\n",
> >> + uacce->qf_pg_size[UACCE_QFRT_DUS] << PAGE_SHIFT);
> >> +}
> >> +
> >> +static DEVICE_ATTR_RO(id);
> >> +static DEVICE_ATTR_RO(api);
> >> +static DEVICE_ATTR_RO(numa_distance);
> >> +static DEVICE_ATTR_RO(node_id);
> >> +static DEVICE_ATTR_RO(flags);
> >> +static DEVICE_ATTR_RO(available_instances);
> >> +static DEVICE_ATTR_RO(algorithms);
> >> +static DEVICE_ATTR_RO(qfrt_mmio_size);
> >> +static DEVICE_ATTR_RO(qfrt_dus_size);
> >> +
> >> +static struct attribute *uacce_dev_attrs[] = {
> >> + &dev_attr_id.attr,
> >> + &dev_attr_api.attr,
> >> + &dev_attr_node_id.attr,
> >> + &dev_attr_numa_distance.attr,
> >> + &dev_attr_flags.attr,
> >> + &dev_attr_available_instances.attr,
> >> + &dev_attr_algorithms.attr,
> >> + &dev_attr_qfrt_mmio_size.attr,
> >> + &dev_attr_qfrt_dus_size.attr,
> >> + NULL,
> >> +};
> >> +ATTRIBUTE_GROUPS(uacce_dev);
> >> +
> >> +static void uacce_release(struct device *dev)
> >> +{
> >> + struct uacce_device *uacce = to_uacce_device(dev);
> >> +
> >> + kfree(uacce);
> >> +}
> >> +
> >> +/**
> >> + * uacce_register - register an accelerator
> > This isn't quite correct kernel-doc. Please run the
> > generation script over it and fix any warnings.
> >
> > uacce_register() - register an accelerator
> Sure, will add (), though no warning reported from ./scripts/kernel-doc

I checked that one for another review yesterday. Seems the kernel
suggested kernel-doc style isn't actually enforced and the brackets
are optional for functions. It assumes anything it hasn't identified
as something else must be a function hence this is the one case where
careful matching doesn't apply (unlike struct, enum etc).

> >
> >> + * @parent: pointer of uacce parent device
> >> + * @interface: pointer of uacce_interface for register
> >> + */
> >> +struct uacce_device *uacce_register(struct device *parent,
> >> + struct uacce_interface *interface)
> >> +{
> >> + unsigned int flags = interface->flags;
> >> + struct uacce_device *uacce;
> >> + int ret;
> >> +
> >> + uacce = kzalloc(sizeof(struct uacce_device), GFP_KERNEL);
> >> + if (!uacce)
> >> + return ERR_PTR(-ENOMEM);
> >> +
> >> + if (flags & UACCE_DEV_SVA) {
> >> + ret = iommu_dev_enable_feature(parent, IOMMU_DEV_FEAT_SVA);
> >> + if (ret)
> >> + flags &= ~UACCE_DEV_SVA;
> >> + }
> >> +
> >> + uacce->pdev = parent;
> >> + uacce->flags = flags;
> >> + uacce->ops = interface->ops;
> >> +
> >> + ret = xa_alloc(&uacce_xa, &uacce->dev_id, uacce, xa_limit_32b,
> >> + GFP_KERNEL);
> >> + if (ret < 0)
> >> + goto err_with_uacce;
> >> +
> >> + uacce->cdev = cdev_alloc();
> > If we can embed this (see below) then use cdev_init instead.
> >
> >> + if (!uacce->cdev) {
> >> + ret = -ENOMEM;
> >> + goto err_with_xa;
> >> + }
> >> +
> >> + INIT_LIST_HEAD(&uacce->qs);
> >> + mutex_init(&uacce->q_lock);
> >> + uacce->cdev->ops = &uacce_fops;
> >> + uacce->cdev->owner = THIS_MODULE;
> >> + device_initialize(&uacce->dev);
> >> + uacce->dev.devt = MKDEV(MAJOR(uacce_devt), uacce->dev_id);
> >> + uacce->dev.class = uacce_class;
> >> + uacce->dev.groups = uacce_dev_groups;
> >> + uacce->dev.parent = uacce->pdev;
> >> + uacce->dev.release = uacce_release;
> >> + dev_set_name(&uacce->dev, "%s-%d", interface->name, uacce->dev_id);
> >> + ret = cdev_device_add(uacce->cdev, &uacce->dev);
> >> + if (ret)
> >> + goto err_with_xa;
> >> +
> >> + return uacce;
> >> +
> >> +err_with_xa:
> >> + if (uacce->cdev)
> >> + cdev_del(uacce->cdev);
> > Why not use a separate label to handle the above rather than checking if
> > it's set?
> ok,
> >
> >> + xa_erase(&uacce_xa, uacce->dev_id);
> >> +err_with_uacce:
> >> + if (flags & UACCE_DEV_SVA)
> >> + iommu_dev_disable_feature(uacce->pdev, IOMMU_DEV_FEAT_SVA);
> >> + kfree(uacce);
> >> + return ERR_PTR(ret);
> >> +}
> >> +EXPORT_SYMBOL_GPL(uacce_register);
> >> +
> >> +/**
> >> + * uacce_unregister - unregisters an accelerator
> >> + * @uacce: the accelerator to unregister
> >> + */
> >> +void uacce_unregister(struct uacce_device *uacce)
> >> +{
> >> + if (!uacce)
> >> + return;
> >> +
> > I'd like to see a comment here on why we are doing things not unwinding
> > actions from uacce_register.
> OK will add comments.
> Here is "ensure no open queue remains"
> >> + mutex_lock(&uacce->q_lock);
> >> + if (!list_empty(&uacce->qs)) {
> >> + struct uacce_queue *q;
> >> +
> >> + list_for_each_entry(q, &uacce->qs, list) {
> >> + uacce_put_queue(q);
> >> + if (uacce->flags & UACCE_DEV_SVA)
> >> + iommu_sva_unbind_device(q->handle);
> >> + }
> >> + }
> >> + mutex_unlock(&uacce->q_lock);
> >> +
> > For these next parts which are the unwind of uacce_register, why are they not
> > in the reverse order of what is happening in there (where possible given
> > device lifespan). That is why do we not disable the iommu feature much later?
> First close all queues, then disable sva feature.
> >
> >> + if (uacce->flags & UACCE_DEV_SVA)
> >> + iommu_dev_disable_feature(uacce->pdev, IOMMU_DEV_FEAT_SVA);
> >> +
> >> + cdev_device_del(uacce->cdev, &uacce->dev);
> >> + xa_erase(&uacce_xa, uacce->dev_id);
> >> + put_device(&uacce->dev);
> >> +}
> >> +EXPORT_SYMBOL_GPL(uacce_unregister);
> >> +
> >> +static int __init uacce_init(void)
> >> +{
> >> + int ret;
> >> +
> >> + uacce_class = class_create(THIS_MODULE, UACCE_NAME);
> >> + if (IS_ERR(uacce_class))
> >> + return PTR_ERR(uacce_class);
> >> +
> >> + ret = alloc_chrdev_region(&uacce_devt, 0, MINORMASK, UACCE_NAME);
> >> + if (ret) {
> >> + class_destroy(uacce_class);
> >> + return ret;
> > drop the return ret out of these brackets. i.e.
> >
> > if (ret)
> > class_destroy(uacce_class)
> >
> > return ret;
> sure, thanks
> >
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static __exit void uacce_exit(void)
> >> +{
> >> + unregister_chrdev_region(uacce_devt, MINORMASK);
> >> + class_destroy(uacce_class);
> >> +}
> >> +
> >> +subsys_initcall(uacce_init);
> >> +module_exit(uacce_exit);
> >> +
> >> +MODULE_LICENSE("GPL");
> >> +MODULE_AUTHOR("Hisilicon Tech. Co., Ltd.");
> >> +MODULE_DESCRIPTION("Accelerator interface for Userland applications");
> >> diff --git a/include/linux/uacce.h b/include/linux/uacce.h
> >> new file mode 100644
> >> index 0000000..04c8643
> >> --- /dev/null
> >> +++ b/include/linux/uacce.h
> >> @@ -0,0 +1,163 @@
> >> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> >> +#ifndef _LINUX_UACCE_H
> >> +#define _LINUX_UACCE_H
> >> +
> >> +#include <linux/cdev.h>
> >> +#include <uapi/misc/uacce/uacce.h>
> >> +
> >> +#define UACCE_NAME "uacce"
> >> +#define UACCE_QFRT_MAX 16
> > What does QFRT stand for?
> change to UACCE_MAX_REGION

Much better

> >> +#define UACCE_MAX_NAME_SIZE 64
> >> +
> >> +struct uacce_queue;
> >> +struct uacce_device;
> >> +
> >> +/**
> >> + * enum uacce_qfr_flag: queue file flag:
> >> + * @UACCE_QFRF_SELFMT: self maintained qfr
> >> + */
> >> +enum uacce_qfr_flag {
> >> + UACCE_QFRF_SELFMT = BIT(0),
> >> +};
> > Same issue with enums for flags. Doesn't make much sense to me.
> > Only one value can be taken which doesn't make it a flag.
> >
> >> +
> >> +/**
> >> + * struct uacce_qfile_region - structure of queue file region
> >> + * @type: type of the qfr
> >> + * @flags: flags of qfr
> >> + * @prot: qfr protection flag
> >> + */
> >> +struct uacce_qfile_region {
> >> + enum uacce_qfrt type;
> >> + enum uacce_qfr_flag flags;
> >> + u32 prot;
> >> +};
> >> +
> >> +/**
> >> + * struct uacce_ops - uacce device operations
> >> + * @get_available_instances: get available instances left of the device
> >> + * @get_queue: get a queue from the device
> >> + * @put_queue: free a queue to the device
> >> + * @start_queue: make the queue start work after get_queue
> >> + * @stop_queue: make the queue stop work before put_queue
> >> + * @is_q_updated: check whether the task is finished
> >> + * @mask_notify: mask the task irq of queue
> >> + * @mmap: mmap addresses of queue to user space
> >> + * @reset: reset the uacce device
> >> + * @reset_queue: reset the queue
> >> + * @ioctl: ioctl for user space users of the queue
> >> + */
> >> +struct uacce_ops {
> >> + int (*get_available_instances)(struct uacce_device *uacce);
> >> + int (*get_queue)(struct uacce_device *uacce, unsigned long arg,
> >> + struct uacce_queue *q);
> >> + void (*put_queue)(struct uacce_queue *q);
> >> + int (*start_queue)(struct uacce_queue *q);
> >> + void (*stop_queue)(struct uacce_queue *q);
> >> + int (*is_q_updated)(struct uacce_queue *q);
> >> + void (*mask_notify)(struct uacce_queue *q, int event_mask);
> >> + int (*mmap)(struct uacce_queue *q, struct vm_area_struct *vma,
> >> + struct uacce_qfile_region *qfr);
> >> + int (*reset)(struct uacce_device *uacce);
> >> + int (*reset_queue)(struct uacce_queue *q);
> > Some of these aren't used on only existing driver. Introduce them only
> > in the series that uses them.
> OK
> >
> >> + long (*ioctl)(struct uacce_queue *q, unsigned int cmd,
> >> + unsigned long arg);
> >> +};
> >> +
> >> +/**
> >> + * struct uacce_interface
> > I think this needs a description for kernel doc (even if it's obvious!)
> > Could be wrong though.
> OK
> >
> >> + * @name: the uacce device name. Will show up in sysfs
> >> + * @flags: uacce device attributes
> >> + * @ops: pointer to the struct uacce_ops
> >> + *
> >> + * This structure is used for the uacce_register()
> >> + */
> >> +struct uacce_interface {
> >> + char name[UACCE_MAX_NAME_SIZE];
> >> + enum uacce_dev_flag flags;
> >> + struct uacce_ops *ops;
> >> +};
> >> +
> >> +enum uacce_q_state {
> >> + UACCE_Q_INIT,
> >> + UACCE_Q_STARTED,
> >> + UACCE_Q_ZOMBIE,
> >> +};
> >> +
> >> +/**
> >> + * struct uacce_queue
> >> + * @uacce: pointer to uacce
> >> + * @priv: private pointer
> >> + * @wait: wait queue head
> >> + * @pasid: pasid of the queue
> >> + * @pid: pid of the process using the queue
> >> + * @handle: iommu_sva handle return from iommu_sva_bind_device
> >> + * @list: queue list
> >> + * @qfrs: pointer of qfr regions
> >> + * @state: queue state machine
> >> + */
> >> +struct uacce_queue {
> >> + struct uacce_device *uacce;
> >> + void *priv;
> >> + wait_queue_head_t wait;
> >> + int pasid;
> >> + pid_t pid;
> >> + struct iommu_sva *handle;
> >> + struct list_head list;
> >> + struct uacce_qfile_region *qfrs[UACCE_QFRT_MAX];
> >> + enum uacce_q_state state;
> >> +};
> >> +
> >> +/**
> >> + * struct uacce_device
> >> + * @algs: supported algorithms
> >> + * @api_ver: api version
> >> + * @qf_pg_size: page size of the queue file regions
> >> + * @ops: pointer to the struct uacce_ops
> >> + * @pdev: pointer to the parent device
> >> + * @is_vf: whether virtual function
> >> + * @flags: uacce attributes
> >> + * @dev_id: id of the uacce device
> >> + * @prot: uacce protection flag
> >> + * @cdev: cdev of the uacce
> >> + * @dev: dev of the uacce
> >> + * @priv: private pointer of the uacce
> >> + * @qs: list head of queue->list
> >> + * @q_lock: lock for qs
> >> + */
> >> +struct uacce_device {
> >> + const char *algs;
> >> + const char *api_ver;
> >> + unsigned long qf_pg_size[UACCE_QFRT_MAX];
> >> + struct uacce_ops *ops;
> > Can we make this ops structure a point to a constant struct?
> > I'm guessing it'll be fixed for a given driver.
> OK
> >
> >> + struct device *pdev;
> > Perhaps just call it parent. pdev will be confusing with
> > pci devices.
> OK
> >
> >> + bool is_vf;
> >> + u32 flags;
> >> + u32 dev_id;
> >> + u32 prot;
> >> + struct cdev *cdev;
> > Can we embed the cdev structure rather than use a pointer
> > and separate allocation?
> NO, we can't.
> We originally embed the cdev structure, and Greg reminded us these two
> structure have different lifetime.
> https://lkml.org/lkml/2019/8/28/771

Ok. Fair enough.

> >> + struct device dev;
> >> + void *priv;
> >> + struct list_head qs;
> >> + struct mutex q_lock;
> >> +};
> >> +
> >> +#if IS_ENABLED(CONFIG_UACCE)
> >> +
> >> +struct uacce_device *uacce_register(struct device *parent,
> >> + struct uacce_interface *interface);
> >> +void uacce_unregister(struct uacce_device *uacce);
> >> +
> >> +#else /* CONFIG_UACCE */
> >> +
> >> +static inline
> >> +struct uacce_device *uacce_register(struct device *parent,
> >> + struct uacce_interface *interface)
> >> +{
> >> + return ERR_PTR(-ENODEV);
> >> +}
> >> +
> >> +static inline void uacce_unregister(struct uacce_device *uacce) {}
> >> +
> >> +#endif /* CONFIG_UACCE */
> >> +
> >> +#endif /* _LINUX_UACCE_H */
> >> diff --git a/include/uapi/misc/uacce/uacce.h b/include/uapi/misc/uacce/uacce.h
> >> new file mode 100644
> >> index 0000000..a4f9378
> >> --- /dev/null
> >> +++ b/include/uapi/misc/uacce/uacce.h
> >> @@ -0,0 +1,38 @@
> >> +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
> >> +#ifndef _UAPIUUACCE_H
> >> +#define _UAPIUUACCE_H
> >> +
> >> +#include <linux/types.h>
> >> +#include <linux/ioctl.h>
> >> +
> >> +/* UACCE_CMD_START_Q: Start the queue */
> >> +#define UACCE_CMD_START_Q _IO('W', 0)
> >> +
> >> +/**
> >> + * UACCE_CMD_PUT_Q:
> >> + * User actively stop queue and free queue resource immediately
> >> + * Optimization method since close fd may delay
> >> + */
> >> +#define UACCE_CMD_PUT_Q _IO('W', 1)
> >> +
> >> +/**
> >> + * enum uacce_dev_flag: Device flags:
> >> + * @UACCE_DEV_SVA: Shared Virtual Addresses
> >> + * Support PASID
> >> + * Support device page faults (PCI PRI or SMMU Stall)
> >> + */
> >> +enum uacce_dev_flag {
> >> + UACCE_DEV_SVA = BIT(0),
> > As mentioned in docs review, this doesn't look like an enum to me.
> > Just use #define for the bit and a suitable sized integer for any
> > calls using it.
> OK, but there are still more features in the future patch.
That's not the issue. An enum should (more or less) use concurrent values.

A = 0,
B = 1,
C = 2, etc
and an instance of it should only take one of them.

Once you are using it as values for a bitmap, the typing becomes irrelevant
as you can't really use it to enforce anything, so you should just use.

#define UACCE_DEV_SVA BIT(0)
#define UACCE_DEV_SOMETHING BIT(1) etc

>
> Thanks
>

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