linux-kernel - Re: [PATCH] drm/fb-helper: Don't call dirty callback for untouched clips

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Date:   Fri, 21 Oct 2016 21:02:27 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Takashi Iwai <tiwai@...e.de>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Noralf Trønnes <noralf@...nnes.org>,
        David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH] drm/fb-helper: Don't call dirty callback for untouched
 clips

On Fri, Oct 21, 2016 at 08:19:03PM +0200, Daniel Vetter wrote:
> On Fri, Oct 21, 2016 at 01:57:28PM +0100, Chris Wilson wrote:
> > I think of a use for sending an empty clip: where you don't want to
> > push any new pixel data, but you do want to be sure that the pipeline
> > has been flushed.
> 
> What exactly should an empty rectangle flush out? It's a bit unclear, but
> for speed I guess drivers should be allowed to make dirty async ...

No idea! I'm just speculating that I can see a use for a dirtyfb barrier
even with an empty cliprect. Empty clips are a useful distinction
elsewhere that I would suggest not forbidding them outright but defining
their behaviour.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre