linux-kernel - Re: [PATCH 03/10] drm/sun4i: Don't pretend to handle ARGB8888 with the frontend

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Message-ID: <20180322161204.dpi6puzvosesm5xt@flea>
Date:   Thu, 22 Mar 2018 17:12:04 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Sean Paul <seanpaul@...omium.org>
Subject: Re: [PATCH 03/10] drm/sun4i: Don't pretend to handle ARGB8888 with
 the frontend

Hi,

Beside the discussion with Chen-Yu,

On Wed, Mar 21, 2018 at 04:28:57PM +0100, Paul Kocialkowski wrote:
> It turns out that the frontend is not capable of preserving the alpha
> component (that is always set to 0xff), so only support XRGB8888
> instead.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> ---

[...]

> diff --git a/drivers/gpu/drm/sun4i/sun4i_layer.c b/drivers/gpu/drm/sun4i/sun4i_layer.c
> index eb93df445a10..15238211a61a 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_layer.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_layer.c
> @@ -100,9 +100,9 @@ static void sun4i_backend_layer_atomic_update(struct drm_plane *plane,
>  		sun4i_frontend_update_coord(frontend, plane);
>  		sun4i_frontend_update_buffer(frontend, plane);
>  		sun4i_frontend_update_formats(frontend, plane,
> -					      DRM_FORMAT_ARGB8888);
> +					      DRM_FORMAT_XRGB8888);
>  		sun4i_backend_update_layer_frontend(backend, layer->id, plane,
> -						    DRM_FORMAT_ARGB8888);
> +						    DRM_FORMAT_XRGB8888);

Even though it's slightly related, these changes should be justified
in the commit log. From what you currently explain, this makes 0
difference, since XRGB and ARGB with an alpha component to 0xff is
exactly the same thing.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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