On 11/23/22 02:02, Randy Dunlap wrote: > Hi Arnd, > > On 11/23/22 01:08, Arnd Bergmann wrote: >> On Wed, Nov 23, 2022, at 04:16, Randy Dunlap wrote: >>> Fix build when CONFIG_FB_OF=y and CONFIG_DRM_OFDRM=m. >>> When the latter symbol is =m, kconfig downgrades (limits) the 'select's >>> under FB_OF to modular (=m). This causes undefined symbol references: >>> >>> powerpc64-linux-ld: drivers/video/fbdev/offb.o:(.data.rel.ro+0x58): >>> undefined reference to `cfb_fillrect' >>> powerpc64-linux-ld: drivers/video/fbdev/offb.o:(.data.rel.ro+0x60): >>> undefined reference to `cfb_copyarea' >>> powerpc64-linux-ld: drivers/video/fbdev/offb.o:(.data.rel.ro+0x68): >>> undefined reference to `cfb_imageblit' >>> >>> Fix this by allowing FB_OF any time that DRM_OFDRM != y so that the >>> selected FB_CFB_* symbols will become =y instead of =m. >>> >>> In tristate logic (for DRM_OFDRM), this changes the dependency from >>> !DRM_OFDRM == 2 - 1 == 1 => modular only (or disabled) >>> to (boolean) >>> DRM_OFDRM != y == y, allowing the 'select's to cause the >>> FB_CFB_* symbols to =y instead of =m. >>> >> >> Is it actually a useful configuration to have OFDRM=m and >> FB_OF=y though? I would expect in that case that the OFDRM >> driver never binds to a device because it's already owned >> by FB_OF. >> >>> diff -- a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig >>> --- a/drivers/video/fbdev/Kconfig >>> +++ b/drivers/video/fbdev/Kconfig >>> @@ -455,7 +455,7 @@ config FB_ATARI >>> config FB_OF >>> bool "Open Firmware frame buffer device support" >>> depends on (FB = y) && PPC && (!PPC_PSERIES || PCI) >>> - depends on !DRM_OFDRM >>> + depends on DRM_OFDRM != y >>> select APERTURE_HELPERS >> >> I would instead make this 'depends on DRM_OFDRM=n', which >> completely eliminates configs that have both driver enabled. > > Yep, that works for me. Thanks. > > Thomas, Michal, are you OK with that change? > >> A nicer change would be to make FB_OF a tristate symbol, >> which makes it possible to load one of the two modules if >> both are enabled =m, while only allowing one of them to >> be =y if the other is completely disabled. It looks like >> offb was originally written to be usable as a loadable module, >> but Kconfig has prevented this since at least the start of >> the git history. ISTM that a distro would prefer to have both DFM_OFDRM and FB_OF as tristate symbols that could both be built as loadable modules, as Arnd describes above. I'll look into that. -- ~Randy
