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

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Date:   Tue, 22 Nov 2022 19:16:05 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     linux-kernel@...r.kernel.org
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Michal Suchánek <msuchanek@...e.de>,
        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: [PATCH -next] fbdev: offb: allow build when DRM_OFDRM=m

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
---
 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