linux-kernel - Re: [PATCH v2 16/19] drm/sun4i: backend: Assign the pipes automatically

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Date:   Mon, 29 Jan 2018 10:22:54 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        thomas@...sch.nl
Subject: Re: [PATCH v2 16/19] drm/sun4i: backend: Assign the pipes automatically

On Mon, Jan 22, 2018 at 6:35 PM, Maxime Ripard
<maxime.ripard@...e-electrons.com> wrote:
> Since we now have a way to enforce the zpos, check for the number of alpha
> planes, the only missing part is to assign our pipe automatically instead
> of hardcoding it.
>
> The algorithm is quite simple, but requires two iterations over the list of
> planes.
>
> In the first one (which is the same one that we've had to check for alpha,
> the frontend usage, and so on), we order the planes by their zpos.
>
> We can then do a second iteration over that array by ascending zpos
> starting with the pipe 0. When and if we encounter our alpha plane, we put
> it and all the other subsequent planes in the second pipe.
>
> And since we have runtime checks and pipe assignments now, we can just
> remove the static declaration of the planes we used to have.

It would be slightly better if you could split this out into a separate
patch. It's not immediately obvious to others that the changes to
sun4i_layer.c are self-contained, while the change to sun4i_layer.h
is part of the new pipeline tracking thing. Plus I think the way you
structured everything means it won't break if you split it out.

Reviewed-by: Chen-Yu Tsai <wens@...e.org>