On Wed, 27 Oct 2021, Javier Martinez Canillas <javierm@xxxxxxxxxx> wrote: > On 10/27/21 14:18, Arnd Bergmann wrote: >> On Wed, Oct 27, 2021 at 1:47 PM Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: > > [snip] > >>> 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. > > Indeed, you are correct that's not semantically correct. > >> >> Right, how about this change on top? >> >> --- a/drivers/gpu/drm/Kconfig >> +++ b/drivers/gpu/drm/Kconfig >> @@ -117,9 +117,8 @@ config DRM_DEBUG_MODESET_LOCK >> >> config DRM_FBDEV_EMULATION >> bool "Enable legacy fbdev support for your modesetting driver" >> - depends on DRM >> - depends on FB=y || FB=DRM >> - select DRM_KMS_HELPER >> + depends on DRM_KMS_HELPER >> + depends on FB=y || FB=DRM_KMS_HELPER >> select FB_CFB_FILLRECT >> select FB_CFB_COPYAREA >> select FB_CFB_IMAGEBLIT >> >> That would probably make it work for DRM=y, FB=m, DRM_KMS_HELPER=m, >> but it needs more randconfig testing, which I can help with. >> >>> 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. >> >> This is something we can't easily express in Kconfig, as we can't add the >> dependency to a symbol that only gets selected by other drivers, which >> is why the dependency has to be in the user-visible symbol, >> in this case DRM_FBDEV_EMULATION. >> > > Why the dependency has to be in a user-visible symbol? What could be the > problem with having something like: > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > index cea777ae7fb9..f80b404946ca 100644 > --- a/drivers/gpu/drm/Kconfig > +++ b/drivers/gpu/drm/Kconfig > @@ -82,6 +82,7 @@ config DRM_DEBUG_SELFTEST > config DRM_KMS_HELPER > tristate > depends on DRM > + depends on (DRM_FBDEV_EMULATION && FB) || !DRM_FBDEV_EMULATION To me, this seems like the right solution. Depend on FB if DRM_FBDEV_EMULATION is enabled. That's exactly what the relationship is. BR, Jani. > help > CRTC helpers for KMS drivers. > > @@ -104,7 +105,6 @@ config DRM_FBDEV_EMULATION > bool "Enable legacy fbdev support for your modesetting driver" > depends on DRM > depends on FB > - select DRM_KMS_HELPER > select FB_CFB_FILLRECT > select FB_CFB_COPYAREA > select FB_CFB_IMAGEBLIT > > Best regards, -- Jani Nikula, Intel Open Source Graphics Center
