linux-kernel - Re: [PATCH -next] fbdev: offb: allow build when DRM

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Date:   Wed, 23 Nov 2022 09:38:42 +0100
From:   Michal Suchánek <msuchanek@...e.de>
To:     Thomas Zimmermann <tzimmermann@...e.de>
Cc:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        linuxppc-dev@...ts.ozlabs.org, Daniel Vetter <daniel@...ll.ch>,
        Helge Deller <deller@....de>, linux-fbdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH -next] fbdev: offb: allow build when DRM_OFDRM=m

On Wed, Nov 23, 2022 at 09:02:54AM +0100, Thomas Zimmermann wrote:
> 
> Am 23.11.22 um 04:16 schrieb Randy Dunlap:
> > 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.
> > 
> > Fixes: c8a17756c425 ("drm/ofdrm: Add ofdrm for Open Firmware framebuffers")
> > Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> > Suggested-by: Masahiro Yamada <masahiroy@...nel.org>
> > Cc: Thomas Zimmermann <tzimmermann@...e.de>
> > Cc: Michal Suchánek <msuchanek@...e.de>
> > Cc: linuxppc-dev@...ts.ozlabs.org
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: Helge Deller <deller@....de>
> > Cc: linux-fbdev@...r.kernel.org
> > Cc: dri-devel@...ts.freedesktop.org
> 
> Acked-by: Thomas Zimmermann <tzimmermann@...e.de>

Tested-by: Michal Suchánek <msuchanek@...e.de>

> 
> > ---
> >   drivers/video/fbdev/Kconfig |    2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > 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
> >   	select FB_CFB_FILLRECT
> >   	select FB_CFB_COPYAREA
> 
> -- 
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Ivo Totev