Re: [PATCH RFC] fpga: add FPGA Bus device framework

[Alan Tull]

On Wed, Aug 2, 2017 at 7:19 AM, Wu Hao <hao.wu@xxxxxxxxx> wrote:
> This patch is a RFC patch which replaces the patch[1] which
> creates 'fpga-dev' class as container device. It introduces
> a 'fpga' bus type, and provides interfaces to create/destroy
> fpga bus devices. This fpga bus device only could be used as
> a container device, and no drivers needed for it.
>
> There is no interface change, so this patch could be used
> together with other patches of the original patch set[2].
>

I am wondering whether this could be added to fpga-bridge.c so that
fpga-bridge becomes the fpga bus and fpga bus devices are under it.
The reasons for doing this are discussed in the other thread.

> This following APIs are provided by FPGA Bus device framework:
> * fpga_dev_create
>   Create fpga bus device under the given parent device.
> * fpga_dev_destroy
>   Destroy fpga bus device

This is being used in such that each fpga-dev is a container for
platform devices rather than fpga devices.  That's not what I was
expecting. :)

Alan

>
> The following sysfs files are created:
> * /sys/bus/fpga/devices/<fpga.x>/name
>   Name of the fpga bus device.
>
> [1] http://marc.info/?l=linux-fpga&m=149844237209829&w=2
> [2] http://marc.info/?l=linux-fpga&m=149844232609819&w=2
>
> Signed-off-by: Wu Hao <hao.wu@xxxxxxxxx>
> ---
>  Documentation/ABI/testing/sysfs-bus-fpga |   5 ++
>  drivers/fpga/Kconfig                     |   6 ++
>  drivers/fpga/Makefile                    |   3 +
>  drivers/fpga/fpga-dev.c                  | 132 +++++++++++++++++++++++++++++++
>  include/linux/fpga/fpga-dev.h            |  31 ++++++++
>  5 files changed, 177 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-fpga
>  create mode 100644 drivers/fpga/fpga-dev.c
>  create mode 100644 include/linux/fpga/fpga-dev.h
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-fpga b/Documentation/ABI/testing/sysfs-bus-fpga
> new file mode 100644
> index 0000000..414e946
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-fpga
> @@ -0,0 +1,5 @@
> +What:          /sys/bus/fpga/devices/<fpga.x>/name
> +Date:          August 2017
> +KernelVersion: 4.13
> +Contact:       Wu Hao <hao.wu@xxxxxxxxx>
> +Description:   Name of FPGA bus device
> diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> index d89eb52..b97a90e 100644
> --- a/drivers/fpga/Kconfig
> +++ b/drivers/fpga/Kconfig
> @@ -12,6 +12,12 @@ config FPGA
>           manager drivers.
>
>  if FPGA
> +config FPGA_DEVICE
> +       tristate "FPGA Bus Device Framework"
> +       help
> +         Say Y here if you want support for FPGA Bus devices from the
> +         kernel. The FPGA Bus Device Framework adds a FPGA Bus type and
> +         provide interfaces to create FPGA devices on the bus.
>
>  config FPGA_REGION
>         tristate "FPGA Region"
> diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> index 08fc728..3eb254e 100644
> --- a/drivers/fpga/Makefile
> +++ b/drivers/fpga/Makefile
> @@ -5,6 +5,9 @@
>  # Core FPGA Manager Framework
>  obj-$(CONFIG_FPGA)                     += fpga-mgr.o
>
> +# FPGA Bus Device Framework
> +obj-$(CONFIG_FPGA_DEVICE)              += fpga-dev.o
> +
>  # FPGA Manager Drivers
>  obj-$(CONFIG_FPGA_MGR_ICE40_SPI)       += ice40-spi.o
>  obj-$(CONFIG_FPGA_MGR_SOCFPGA)         += socfpga.o
> diff --git a/drivers/fpga/fpga-dev.c b/drivers/fpga/fpga-dev.c
> new file mode 100644
> index 0000000..ddf67bb
> --- /dev/null
> +++ b/drivers/fpga/fpga-dev.c
> @@ -0,0 +1,132 @@
> +/*
> + * FPGA Bus Device Framework Driver
> + *
> + * Copyright (C) 2017 Intel Corporation, Inc.
> + *
> + * This work is licensed under the terms of the GNU GPL version 2. See
> + * the COPYING file in the top-level directory.
> + */
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/fpga/fpga-dev.h>
> +
> +static DEFINE_IDA(fpga_dev_ida);
> +static bool is_bus_registered;

I wouldn't think init will be called more than once.  Did you run into
a problem where it did?

> +
> +static void fpga_dev_release(struct device *dev)
> +{
> +       struct fpga_dev *fdev = to_fpga_dev(dev);
> +
> +       ida_simple_remove(&fpga_dev_ida, fdev->dev.id);
> +       kfree(fdev);
> +}
> +
> +static const struct device_type fpga_dev_type = {
> +       .name           = "fpga_dev",
> +       .release        = fpga_dev_release,
> +};
> +
> +static ssize_t name_show(struct device *dev,
> +                        struct device_attribute *attr, char *buf)
> +{
> +       struct fpga_dev *fdev = to_fpga_dev(dev);
> +
> +       return sprintf(buf, "%s\n", fdev->name);
> +}
> +static DEVICE_ATTR_RO(name);
> +
> +static struct attribute *fpga_dev_attrs[] = {
> +       &dev_attr_name.attr,
> +       NULL,
> +};
> +ATTRIBUTE_GROUPS(fpga_dev);
> +
> +static struct bus_type fpga_bus_type = {
> +       .name           = "fpga",
> +};
> +
> +/**
> + * fpga_dev_create - create a fpga device on fpga bus
> + * @parent: parent device
> + * @name: fpga bus device name
> + *
> + * Return fpga_dev struct for success, error code otherwise.
> + */
> +struct fpga_dev *fpga_dev_create(struct device *parent, const char *name)
> +{
> +       struct fpga_dev *fdev;
> +       int id, ret = 0;
> +
> +       if (WARN_ON(!is_bus_registered))
> +               return ERR_PTR(-ENODEV);
> +
> +       if (!name || !strlen(name)) {
> +               dev_err(parent, "Attempt to register with no name!\n");
> +               return ERR_PTR(-EINVAL);
> +       }
> +
> +       fdev = kzalloc(sizeof(*fdev), GFP_KERNEL);
> +       if (!fdev)
> +               return ERR_PTR(-ENOMEM);
> +
> +       id = ida_simple_get(&fpga_dev_ida, 0, 0, GFP_KERNEL);
> +       if (id < 0) {
> +               ret = id;
> +               goto error_kfree;
> +       }
> +
> +       fdev->name = name;
> +
> +       device_initialize(&fdev->dev);
> +       fdev->dev.type = &fpga_dev_type;
> +       fdev->dev.bus = &fpga_bus_type;
> +       fdev->dev.groups = fpga_dev_groups;
> +       fdev->dev.parent = parent;
> +       fdev->dev.id = id;
> +
> +       ret = dev_set_name(&fdev->dev, "fpga.%d", id);
> +       if (ret)
> +               goto error_device;
> +
> +       ret = device_add(&fdev->dev);
> +       if (ret)
> +               goto error_device;
> +
> +       dev_dbg(fdev->dev.parent, "fpga bus device [%s] created\n", fdev->name);
> +
> +       return fdev;
> +
> +error_device:
> +       ida_simple_remove(&fpga_dev_ida, id);
> +error_kfree:
> +       kfree(fdev);
> +
> +       return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(fpga_dev_create);
> +
> +static int __init fpga_bus_init(void)
> +{
> +       int ret;
> +
> +       pr_info("FPGA Bus Device Framework\n");
> +
> +       ret = bus_register(&fpga_bus_type);
> +       if (ret)
> +               return ret;
> +
> +       is_bus_registered = true;
> +       return 0;
> +}
> +
> +static void __exit fpga_bus_exit(void)
> +{
> +       bus_unregister(&fpga_bus_type);
> +}
> +
> +MODULE_DESCRIPTION("FPGA Bus Device Framework");
> +MODULE_LICENSE("GPL v2");
> +
> +subsys_initcall(fpga_bus_init);
> +module_exit(fpga_bus_exit);
> diff --git a/include/linux/fpga/fpga-dev.h b/include/linux/fpga/fpga-dev.h
> new file mode 100644
> index 0000000..7f6deb4
> --- /dev/null
> +++ b/include/linux/fpga/fpga-dev.h
> @@ -0,0 +1,31 @@
> +/*
> + * FPGA Bus Device Framework driver Header
> + *
> + * Copyright (C) 2017 Intel Corporation, Inc.
> + *
> + * This work is licensed under the terms of the GNU GPL version 2. See
> + * the COPYING file in the top-level directory.
> + */
> +#ifndef _LINUX_FPGA_DEV_H
> +#define _LINUX_FPGA_DEV_H
> +
> +/**
> + * struct fpga_dev - fpga bus device structure
> + * @name: name of fpga bus device
> + * @dev: fpga bus device
> + */
> +struct fpga_dev {
> +       const char *name;
> +       struct device dev;
> +};
> +
> +#define to_fpga_dev(d) container_of(d, struct fpga_dev, dev)
> +
> +struct fpga_dev *fpga_dev_create(struct device *parent, const char *name);
> +
> +static inline void fpga_dev_destroy(struct fpga_dev *fdev)
> +{
> +       device_unregister(&fdev->dev);
> +}
> +
> +#endif
> --
> 1.8.3.1
>