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Some configurations of sysfb outputs require format conversion from framebuffer to scanout buffer. It is a driver bug if the conversion helper is missing, yet it might happen on odd scanout formats. The old code, based on drm_fb_blit(), only detects this situation during the commit's hardware update, which is too late to abort the update. Lookup the correct blit helper as part of the check phase. Then store it in the sysfb plane state. Allows for detection of a missing helper before the commit has started. Also avoids drm_fb_blit()'s large switch statement on each updated scanline. Only a single lookup has to be done. The lookup is in drm_sysfb_get_blit_func(), which only tracks formats supported by sysfb drivers. The lookup happens in sysfb's begin_fb_access helper instead of its atomic_check helper. This allows vesadrm, and possibly other drivers, to implement their own atomic_check without interfering with blit lookups. Vesadrm implements XRGB8888 on top of R8 formats with the help of the atomic_check. Doing the blit lookup in begin_fb_access then always uses the correct CRTC format on all drivers. v2: - vesadrm: use drm_sysfb_plane_helper_begin_fb_access() - fix type in commit description (Javier) Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> Link: https://lore.kernel.org/r/20250918154207.84714-3-tzimmermann@suse.de
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.