linux-kernel - Re: [PATCH] drm/sun4i: Clear encoder->bridge if a bridge is not found

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Date:   Tue, 30 Aug 2016 14:56:22 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     David Airlie <airlied@...ux.ie>, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/sun4i: Clear encoder->bridge if a bridge is not found

Hi,

On Tue, Aug 30, 2016 at 08:22:23PM +0800, Chen-Yu Tsai wrote:
> The KMS helpers (drm_atomic_helper_check_modeset/mode_fixup) pass
> encoder->bridge directly to drm_bridge_mode_fixup, which expects a
> valid pointer, or NULL (in which case it just returns).
> 
> Clear encoder->bridge if a bridge is not found, instead of keeping
> the ERR_PTR value.
> 
> Since other drm_bridge functions also follow this pattern of checking
> for a non-NULL pointer, we can drop the ifs around the calls and just
> pass the pointer directly.
> 
> Fixes: 894f5a9f4b4a ("drm/sun4i: Add bridge support")
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> ---
>  drivers/gpu/drm/sun4i/sun4i_rgb.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_rgb.c b/drivers/gpu/drm/sun4i/sun4i_rgb.c
> index d4e52522ec53..ee0795152a33 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_rgb.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_rgb.c
> @@ -154,8 +154,7 @@ static void sun4i_rgb_encoder_enable(struct drm_encoder *encoder)
>  	if (!IS_ERR(tcon->panel))
>  		drm_panel_enable(tcon->panel);
>  
> -	if (!IS_ERR(encoder->bridge))
> -		drm_bridge_enable(encoder->bridge);
> +	drm_bridge_enable(encoder->bridge);
>  
>  	sun4i_tcon_channel_enable(tcon, 0);
>  }
> @@ -170,8 +169,7 @@ static void sun4i_rgb_encoder_disable(struct drm_encoder *encoder)
>  
>  	sun4i_tcon_channel_disable(tcon, 0);
>  
> -	if (!IS_ERR(encoder->bridge))
> -		drm_bridge_disable(encoder->bridge);
> +	drm_bridge_disable(encoder->bridge);

I'd rather keep those changes, it makes it obvious that it's something
optionnal, that can be set to NULL.

>  	if (!IS_ERR(tcon->panel))
>  		drm_panel_disable(tcon->panel);
> @@ -230,6 +228,9 @@ int sun4i_rgb_init(struct drm_device *drm)
>  		return 0;
>  	}
>  
> +	if (IS_ERR(encoder->bridge))
> +		encoder->bridge = NULL;
> +

And that could be the else condition of the if statement below.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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