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

[Thomas Zimmermann]

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

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2.40.0