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.
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.
Arnd
