On Tue, 13 Jun 2023, Thomas Zimmermann wrote:
> Add the new config option FB_DEVICE. If enabled, fbdev provides
> traditional userspace interfaces in devfs, sysfs and procfs, such
> as /dev/fb0 or /proc/fb.
>
> Modern Linux distrobutions have adopted DRM drivers for graphics
> output and use fbdev only for the kernel's framebuffer console.
> Userspace has also moved on, with no new fbdev code being written
> and existing support being removed.
>
> OTOH, fbdev provides userspace a way of accessing kernel or I/O
> memory, which might compromise the system's security. See the recent
> commit c8687694bb1f ("drm/fbdev-generic: prohibit potential
> out-of-bounds access") for an example. Disabling fbdev userspace
> interfaces is therefore a useful feature to limit unnecessary
> exposure of fbdev code to processes of low privilegues.
>
> Patches 1 to 31 fix various bugs and issues in fbdev-related code.
> In most cases the code uses the fbdev device where it should use
> the Linux hardware device or something else. Most of these patches
> fix existing problems and should therefore be considered in any case.
>
> Patches 32 to 37 refactor the fbdev core code. The patches move
> support for backlights, sysfs, procfs and devfs into separate files
> and hide it behind simple interfaces. These changes will allow to
> easily build the userspace support conditionally.
>
> Patch 38 introduces the config option FB_DEVICE and adapts the fbdev
> core to support it. The field struct fb_info.dev is now optional,
> hence the name of the config option.
>
> Tested on simpledrm and i915, including the device handover.
>
> Future directions: With the support for disabling fbdev userspace
> interfaces in place, it will be possible to make most fbdev drivers'
> file-I/O code in struct fb_ops optional as well.
>
> v3:
> * add missing file fb_chrdev.c
> * fix typo in Kconfig help (Daniel)
> v2:
> * fix fsl-diu-fb and sh7760fb
> * split backlight patches
> * set 'default y' for FB_CONFIG
> * minor fixes and corrections
>
> Thomas Zimmermann (38):
> backlight/bd6107: Compare against struct fb_info.device
> backlight/bd6107: Rename struct bd6107_platform_data.fbdev to 'dev'
> backlight/gpio_backlight: Compare against struct fb_info.device
> backlight/gpio_backlight: Rename field 'fbdev' to 'dev'
> backlight/lv5207lp: Compare against struct fb_info.device
> backlight/lv5207lp: Rename struct lv5207lp_platform_data.fbdev to
> 'dev'
> fbdev/atyfb: Reorder backlight and framebuffer init/cleanup
> fbdev/atyfb: Use hardware device as backlight parent
> fbdev/aty128fb: Reorder backlight and framebuffer init/cleanup
> fbdev/aty128fb: Use hardware device as backlight parent
> fbdev/broadsheetfb: Call device_remove_file() with hardware device
> fbdev/ep93xx-fb: Alloc DMA memory from hardware device
> fbdev/ep93xx-fb: Output messages with fb_info() and fb_err()
> fbdev/ep93xx-fb: Do not assign to struct fb_info.dev
> fbdev/fsl-diu-fb: Output messages with fb_*() helpers
> fbdev/mb862xxfb: Output messages with fb_dbg()
> fbdev/metronomefb: Use hardware device for dev_err()
> fbdev/nvidiafb: Reorder backlight and framebuffer init/cleanup
> fbdev/nvidiafb: Use hardware device as backlight parent
> fbdev/pxa168fb: Do not assign to struct fb_info.dev
> fbdev/radeonfb: Reorder backlight and framebuffer cleanup
> fbdev/radeonfb: Use hardware device as backlight parent
> fbdev/rivafb: Reorder backlight and framebuffer init/cleanup
> fbdev/rivafb: Use hardware device as backlight parent
> fbdev/sh7760fb: Use fb_dbg() in sh7760fb_get_color_info()
> fbdev/sh7760fb: Output messages with fb_dbg()
> fbdev/sh7760fb: Alloc DMA memory from hardware device
> fbdev/sh7760fb: Use hardware device with dev_() output during probe
> fbdev/sm501fb: Output message with fb_err()
> fbdev/smscufx: Detect registered fb_info from refcount
> fbdev/tdfxfb: Set i2c adapter parent to hardware device
> fbdev/core: Pass Linux device to pm_vt_switch_*() functions
> fbdev/core: Move framebuffer and backlight helpers into separate files
> fbdev/core: Add fb_device_{create,destroy}()
> fbdev/core: Move procfs code to separate file
> fbdev/core: Move file-I/O code into separate file
> fbdev/core: Rework fb init code
> fbdev: Make support for userspace interfaces configurable
>
> Documentation/gpu/todo.rst | 13 +
> arch/sh/boards/mach-ecovec24/setup.c | 2 +-
> arch/sh/boards/mach-kfr2r09/setup.c | 2 +-
> drivers/staging/fbtft/Kconfig | 1 +
> drivers/video/backlight/bd6107.c | 2 +-
> drivers/video/backlight/gpio_backlight.c | 6 +-
> drivers/video/backlight/lv5207lp.c | 2 +-
Acked-by: Lee Jones <lee@xxxxxxxxxx>
--
Lee Jones [李琼斯]
