[PATCH 0/6] drm,fbdev: Use fbdev's I/O helpers

[Sui Jingfeng]

Hi,


The whole patch set is tested with fbdev of IGT, on LoongArch with
drm/radeon and efifb driver. Test results say SUCCESS.


On 2023/4/25 22:28, Thomas Zimmermann wrote:
> Make fbdev's built-in helpers for reading and writing I/O and system
> memory available to DRM. Replace DRM's internal helpers.
>
> The first patch resolves a bug that's been in the fbdev code for
> more than 15 years. Makes the read/write helpers work successfully
> with the IGT tests.
>
> Patches 2 to 4 streamline fbdev's file-I/O code and remove a few
> duplicate checks.
>
> Patch 5 moves the default-I/O code into the new helpers fb_cfb_read()
> and fb_cfb_write(); patch 6 uses them in DRM. This allows us to remove
> quite a bit of code from DRM's internal fbdev helpers.
>
> Tested with i915 and simpledrm.
>
> The next step here is to remove the drm_fb_helper_{cfb,sys}_*()
> entirely. They where mostly introduced because fbdev doesn't protect
> it's public interfaces with an CONFIG_FB preprocessor guards. But all
> of DRM driver's fbdev emulation won't be build without CONFIG_FB, so
> this is not an issue in practice. Removing the DRM wrappers will
> further simplify the DRM code.
>
> Thomas Zimmermann (6):
>    fbdev: Return number of bytes read or written
>    fbdev: Use screen_buffer in fb_sys_{read,write}()
>    fbdev: Don't re-validate info->state in fb_ops implementations
>    fbdev: Validate info->screen_{base,buffer} in fb_ops implementations
>    fbdev: Move CFB read and write code into helper functions
>    drm/fb-helper: Use fb_{cfb,sys}_{read, write}()
>
>   drivers/gpu/drm/drm_fb_helper.c        | 174 +------------------------
>   drivers/video/fbdev/cobalt_lcdfb.c     |   6 +
>   drivers/video/fbdev/core/Makefile      |   2 +-
>   drivers/video/fbdev/core/fb_cfb_fops.c | 126 ++++++++++++++++++
>   drivers/video/fbdev/core/fb_sys_fops.c |  36 ++---
>   drivers/video/fbdev/core/fbmem.c       | 111 +---------------
>   drivers/video/fbdev/sm712fb.c          |  10 +-
>   include/linux/fb.h                     |  10 ++
>   8 files changed, 173 insertions(+), 302 deletions(-)
>   create mode 100644 drivers/video/fbdev/core/fb_cfb_fops.c
>