Re: [PATCH] drm/pl111: Remove reverse dependency on DRM_DUMB_VGA_DAC

On Tue, Feb 20, 2018 at 11:29 AM, Thierry Reding
[off-list ref] wrote:

From: Thierry Reding <redacted>

DRM_DUMB_VGA_DAC is a user-visible symbol. Selecting it can cause unmet
direct dependencies such as this (on i386, randconfig):

        warning: (DRM_PL111) selects DRM_DUMB_VGA_DAC which has unmet direct dependencies (HAS_IOMEM && DRM && DRM_BRIDGE && OF)

This is because DRM_DUMB_VGA_DAC depends on OF while DRM_PL111 does not.
It does indirectly depend on OF via the ARM and ARM64 dependencies, but
since it can also be enabled under COMPILE_TEST, randconfig can find a
case where DRM_PL111 is selected without pulling in OF and not meeting
the dependency for DRM_DUMB_VGA_DAC.

Since select is "heavy handed", DRM_DUMB_VGA_DAC is going to be enabled
regardless of the above warning and causes the following build error:

        ../drivers/gpu/drm/bridge/dumb-vga-dac.c: In function 'dumb_vga_probe':
        ../drivers/gpu/drm/bridge/dumb-vga-dac.c:207:13: error: 'struct drm_bridge' has no member named 'of_node'
          vga->bridge.of_node = pdev->dev.of_node;

See Documentation/kbuild/kconfig-language.txt, "reverse dependencies".

Fixes: 49f81d80ab84 ("drm/pl111: Support handling bridge timings")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Archit Taneja <redacted>
Cc: Eric Anholt <redacted>
Signed-off-by: Thierry Reding <redacted>

OK sorry about that, I just get to let the platforms that need the bridge
select it explicitly.
Reviewed-by: Linus Walleij <redacted>

Yours,
Linus Walleij
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