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

From: Eric Anholt <eric@anholt•net>
To: Thierry Reding <thierry.reding@gmail•com>,
	dri-devel@lists•freedesktop.org
Cc: Randy Dunlap <rdunlap@infradead•org>,
	linux-next@vger•kernel.org,
	Laurent Pinchart <laurent.pinchart@ideasonboard•com>
Subject: Re: [PATCH] drm/pl111: Remove reverse dependency on DRM_DUMB_VGA_DAC
Date: Thu, 22 Feb 2018 12:10:46 -0800	[thread overview]
Message-ID: <874lm8aipl.fsf@anholt.net> (raw)
In-Reply-To: <20180220102903.27787-1-thierry.reding@gmail.com>

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Thierry Reding <thierry.reding@gmail•com> writes:

> From: Thierry Reding <treding@nvidia•com>
>
> 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 <architt@codeaurora•org>
> Cc: Eric Anholt <eric@anholt•net>
> Signed-off-by: Thierry Reding <treding@nvidia•com>
> ---
>  drivers/gpu/drm/pl111/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/pl111/Kconfig b/drivers/gpu/drm/pl111/Kconfig
> index 82cb3e60ddc8..e5e2abd66491 100644
> --- a/drivers/gpu/drm/pl111/Kconfig
> +++ b/drivers/gpu/drm/pl111/Kconfig
> @@ -8,7 +8,6 @@ config DRM_PL111
>  	select DRM_GEM_CMA_HELPER
>  	select DRM_BRIDGE
>  	select DRM_PANEL_BRIDGE
> -	select DRM_DUMB_VGA_DAC
>  	select VT_HW_CONSOLE_BINDING if FRAMEBUFFER_CONSOLE
>  	help
>  	  Choose this option for DRM support for the PL111 CLCD controller.
> -- 
> 2.15.1

Reviewed-by: Eric Anholt <eric@anholt•net>

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