"Arnd Bergmann" <arnd@xxxxxxxx> writes: > On Fri, Jul 14, 2023, at 19:16, Javier Martinez Canillas wrote: >> Currently the CONFIG_FB option has to be enabled even if no legacy fbdev >> drivers are needed (e.g: only to have support for framebuffer consoles). >> >> The DRM subsystem has a fbdev emulation layer, but depends on CONFIG_FB >> and so it can only be enabled if that dependency is enabled as well. >> >> That means fbdev drivers have to be explicitly disabled if users want to >> enable CONFIG_FB, only to use fbcon and/or the DRM fbdev emulation layer. >> >> This patch introduces a non-visible CONFIG_FB_CORE symbol that could be >> enabled just to have core support needed for CONFIG_DRM_FBDEV_EMULATION, >> allowing CONFIG_FB to be disabled (and automatically disabling all the >> fbdev drivers). >> >> Nothing from fb_backlight.o and fbmon.o is used by the DRM fbdev emulation >> layer so these two objects can be compiled out when CONFIG_FB is disabled. > > I gave this a spin in my randconfig build setup and found one small > mistake: > Thanks for testing! >> diff --git a/drivers/video/fbdev/core/Makefile >> b/drivers/video/fbdev/core/Makefile >> index 9150bafd9e89..2cd213716c12 100644 >> --- a/drivers/video/fbdev/core/Makefile >> +++ b/drivers/video/fbdev/core/Makefile >> @@ -1,10 +1,10 @@ >> # SPDX-License-Identifier: GPL-2.0 >> obj-$(CONFIG_FB_NOTIFY) += fb_notify.o >> -obj-$(CONFIG_FB) += fb.o >> -fb-y := fb_backlight.o \ >> - fb_info.o \ >> - fbmem.o fbmon.o fbcmap.o \ >> +obj-$(CONFIG_FB_CORE) += fb.o >> +fb-y := fb_info.o \ >> + fbmem.o fbcmap.o \ >> modedb.o fbcvt.o fb_cmdline.o >> fb_io_fops.o >> +fb-$(CONFIG_FB) += fb_backlight.o fbmon.o > > With CONFIG_FB_CORE=y and CONFIG_FB=m, Kbuild does not include > the fb_backlight.o and fbmon.o files in fb.ko because they are not > set to =y, causing link failures for fbdev drivers later: > > ERROR: modpost: "of_get_fb_videomode" [drivers/video/fbdev/clps711x-fb.ko] undefined! > ERROR: modpost: "fb_videomode_from_videomode" [drivers/video/fbdev/atmel_lcdfb.ko] undefined! > ERROR: modpost: "of_get_fb_videomode" [drivers/video/fbdev/imxfb.ko] undefined! > ERROR: modpost: "fb_destroy_modedb" [drivers/video/fbdev/udlfb.ko] undefined! > ERROR: modpost: "fb_edid_to_monspecs" [drivers/video/fbdev/udlfb.ko] undefined! > ERROR: modpost: "fb_destroy_modedb" [drivers/video/fbdev/smscufx.ko] undefined! > ERROR: modpost: "fb_edid_to_monspecs" [drivers/video/fbdev/smscufx.ko] undefined! > ERROR: modpost: "fb_destroy_modedb" [drivers/video/fbdev/uvesafb.ko] undefined! > ERROR: modpost: "fb_validate_mode" [drivers/video/fbdev/uvesafb.ko] undefined! > ERROR: modpost: "fb_get_mode" [drivers/video/fbdev/uvesafb.ko] undefined! > Right, sorry for missing that combination. > > Folding this fixup into the patch makes it work: > > diff --git a/drivers/video/fbdev/core/Makefile b/drivers/video/fbdev/core/Makefile > index 2cd213716c12f..84ddc5d308b58 100644 > --- a/drivers/video/fbdev/core/Makefile > +++ b/drivers/video/fbdev/core/Makefile > @@ -4,7 +4,9 @@ obj-$(CONFIG_FB_CORE) += fb.o > fb-y := fb_info.o \ > fbmem.o fbcmap.o \ > modedb.o fbcvt.o fb_cmdline.o fb_io_fops.o > -fb-$(CONFIG_FB) += fb_backlight.o fbmon.o > +ifdef CONFIG_FB > +fb-y += fb_backlight.o fbmon.o > +endif > fb-$(CONFIG_FB_DEFERRED_IO) += fb_defio.o > fb-$(CONFIG_FB_DEVICE) += fb_chrdev.o \ > fb_procfs.o \ > Perfect, I'll squash your fix in v6. Thanks! -- Best regards, Javier Martinez Canillas Core Platforms Red Hat