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Date:   Sat, 16 Oct 2021 02:58:24 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, Arnd Bergmann <arnd@arndb.de>,
        dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [RESEND] drm/rcar: stop using 'imply' for dependencies
Message-ID: <YWoVoPxq5Hd1S0ph@pendragon.ideasonboard.com>
References: <20210927142629.2016647-1-arnd@kernel.org>
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Hi Arnd,

Thank you for the patch.

On Mon, Sep 27, 2021 at 04:26:23PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> The meaning of the 'imply' keyword has changed recently, and neither the
> old meaning (select the symbol if its dependencies are met) nor the new
> meaning (enable it by default, but let the user set any other setting)
> is what we want here.
> 
> Work around this by adding two more Kconfig options that lead to
> the correct behavior: if DRM_RCAR_USE_CMM and DRM_RCAR_USE_LVDS
> are enabled, that portion of the driver becomes usable, and no
> configuration results in a link error.
> 
> This avoids a link failure:
> 
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_begin':
> rcar_du_crtc.c:(.text+0x1444): undefined reference to `rcar_cmm_setup'
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_enable':
> rcar_du_crtc.c:(.text+0x14d4): undefined reference to `rcar_cmm_enable'
> arm-linux-gnueabi-ld: rcar_du_crtc.c:(.text+0x1548): undefined reference to `rcar_cmm_setup'
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_disable':
> rcar_du_crtc.c:(.text+0x18b8): undefined reference to `rcar_cmm_disable'
> arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_kms.o: in function `rcar_du_modeset_init':
> 
> Link: https://lore.kernel.org/all/20200417155553.675905-5-arnd@arndb.de/
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> This was last posted as part of a longer series to rework the
> DRM dependencies in a more logical way. The rest of the series
> is still open, but this one is needed as a bug fix regardless of
> the rest.

This looks a bit complicated, but at the same time probably as clean as
it can get with the existing Kconfig grammar. I don't believe the needs
of the rcar-du driver are really exotic, so better support for this in
Kconfig would be nice. Until that happens,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Dave or Daniel, I don't have other pending patches for v5.16, could you
pick this one up ? It fixes a build failure in -next.

> ---
>  drivers/gpu/drm/rcar-du/Kconfig | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/Kconfig b/drivers/gpu/drm/rcar-du/Kconfig
> index b47e74421e34..3e588ddba245 100644
> --- a/drivers/gpu/drm/rcar-du/Kconfig
> +++ b/drivers/gpu/drm/rcar-du/Kconfig
> @@ -4,8 +4,6 @@ config DRM_RCAR_DU
>  	depends on DRM && OF
>  	depends on ARM || ARM64
>  	depends on ARCH_RENESAS || COMPILE_TEST
> -	imply DRM_RCAR_CMM
> -	imply DRM_RCAR_LVDS
>  	select DRM_KMS_HELPER
>  	select DRM_KMS_CMA_HELPER
>  	select DRM_GEM_CMA_HELPER
> @@ -14,13 +12,17 @@ config DRM_RCAR_DU
>  	  Choose this option if you have an R-Car chipset.
>  	  If M is selected the module will be called rcar-du-drm.
>  
> -config DRM_RCAR_CMM
> -	tristate "R-Car DU Color Management Module (CMM) Support"
> -	depends on DRM && OF
> +config DRM_RCAR_USE_CMM
> +	bool "R-Car DU Color Management Module (CMM) Support"
>  	depends on DRM_RCAR_DU
> +	default DRM_RCAR_DU
>  	help
>  	  Enable support for R-Car Color Management Module (CMM).
>  
> +config DRM_RCAR_CMM
> +	def_tristate DRM_RCAR_DU
> +	depends on DRM_RCAR_USE_CMM
> +
>  config DRM_RCAR_DW_HDMI
>  	tristate "R-Car Gen3 and RZ/G2 DU HDMI Encoder Support"
>  	depends on DRM && OF
> @@ -28,15 +30,20 @@ config DRM_RCAR_DW_HDMI
>  	help
>  	  Enable support for R-Car Gen3 or RZ/G2 internal HDMI encoder.
>  
> +config DRM_RCAR_USE_LVDS
> +	bool "R-Car DU LVDS Encoder Support"
> +	depends on DRM_BRIDGE && OF
> +	default DRM_RCAR_DU
> +	help
> +	  Enable support for the R-Car Display Unit embedded LVDS encoders.
> +
>  config DRM_RCAR_LVDS
> -	tristate "R-Car DU LVDS Encoder Support"
> -	depends on DRM && DRM_BRIDGE && OF
> +	def_tristate DRM_RCAR_DU
> +	depends on DRM_RCAR_USE_LVDS
>  	select DRM_KMS_HELPER
>  	select DRM_PANEL
>  	select OF_FLATTREE
>  	select OF_OVERLAY
> -	help
> -	  Enable support for the R-Car Display Unit embedded LVDS encoders.
>  
>  config DRM_RCAR_VSP
>  	bool "R-Car DU VSP Compositor Support" if ARM

-- 
Regards,

Laurent Pinchart