On Thu, 30 Sep 2021, Daniel Vetter daniel@ffwll.ch wrote:
On Mon, Sep 27, 2021 at 09:23:45AM -0700, Kees Cook wrote:
On Mon, Sep 27, 2021 at 04:28:02PM +0200, Arnd Bergmann wrote:
From: Arnd Bergmann arnd@arndb.de
With CONFIG_FB=m and CONFIG_DRM=y, we get a link error in the fb helper:
aarch64-linux-ld: drivers/gpu/drm/drm_fb_helper.o: in function `drm_fb_helper_alloc_fbi': (.text+0x10cc): undefined reference to `framebuffer_alloc'
Tighten the dependency so it is only allowed in the case that DRM can link against FB.
Fixes: f611b1e7624c ("drm: Avoid circular dependencies for CONFIG_FB") Link: https://lore.kernel.org/all/20210721152211.2706171-1-arnd@kernel.org/ Signed-off-by: Arnd Bergmann arnd@arndb.de
Thanks for fixing this!
Reviewed-by: Kees Cook keescook@chromium.org
Stuffed into drm-misc-next.
The problem is, I don't think the patch is semantically correct.
drm_fb_helper.o is not part of drm.ko, it's part of drm_kms_helper.ko. This adds some sort of indirect dependency via DRM which might work, maybe by coincidence, maybe not - but it's certainly not obvious.
The likely culprit is, again, the overuse of select, and in this case select DRM_KMS_HELPER. And DRM_KMS_HELPER should depend on FB if DRM_FBDEV_EMULATION=y. That's the problem.
All of the drm Kconfigs could use an overhaul to be semantically correct, but that's a hill nobody wants to die on. Instead we keep piling up tweaks to paper over the issues, ad infinitum.
(And this ties to a previous comment I had about the organization of files under drm/, a hundred files in one big lump that belong to different modules, and it's not helping people figure out the dependencies.)
BR, Jani.
PS. I was brought here via [1] which is another complicated "fix" to the same problem.
[1] https://lore.kernel.org/r/20211027072044.4105113-1-javierm@redhat.com