Re: [igt-dev] [PATCH i-g-t 1/2] lib/igt_fb: Use cairo conversion in igt_fb_convert_with_stride, v3.

From: Maxime Ripard <maxime.ripard@bootlin.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: igt-dev@lists.freedesktop.org
Subject: Re: [igt-dev] [PATCH i-g-t 1/2] lib/igt_fb: Use cairo conversion in igt_fb_convert_with_stride, v3.
Date: Mon, 8 Apr 2019 10:50:35 +0200	[thread overview]
Message-ID: <20190408085035.jduw3j5wcjm7dbpt@flea> (raw)
In-Reply-To: <c2d9d711-74a8-faaf-2230-eb157ce9a3d0@linux.intel.com>

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Hi Maarten

On Fri, Apr 05, 2019 at 05:38:32PM +0200, Maarten Lankhorst wrote:
> Op 05-04-2019 om 15:54 schreef Paul Kocialkowski:
> > Hi,
> >
> > Le vendredi 05 avril 2019 à 14:52 +0200, Maarten Lankhorst a écrit :
> >> Ever since commit 3fa65f4b532bd9a5b ("fb: Add support for conversions
> >> through pixman") we can generate a valid cairo surface for any plane,
> >> use this to avoid having to implement our own conversion routine.
> >>
> >> Instead of duplicating this functionality in igt_fb_convert_with_stride,
> >> we can simply convert this to a few cairo calls, because we now support
> >> cairo calls to any of the supported framebuffer formats.
> > I don't think this is the case: cairo *only* takes linear buffers, so
> > we need the explicit tiling conversion step after having converted to a
> > new format with fb_convert. I don't see how it could work otherwise.
> >
> > Note that in igt, we're only interested in converting from linear to
> > tiled, not the other way round (for now, at least), so that's the
> > pipeline that the helper asssumes.
>
> We have code to handle this exact conversion in i-g-t already, both
> ways, see igt_get_cairo_surface(). :)
>
> You should be able to extend create_cairo_surface__convert() to
> handle broadcom tiling as well,
>
> I didn't see a function to convert from tiled to untiled, else I
> would have plugged it in for you.

That might be a bit dumb, but why do we need to use cairo all the
time in the first place?

That seems like a waste of resources when the only thing you want to
do is a conversion of one buffer to the other.

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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