RE: [PATCH 01/14] drm: add new plane property FB_DAMAGE_CLIPS to send damage during plane update

From: Deepak Singh Rawat <drawat@vmware.com>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>,
	linux-graphics-maintainer <linux-graphics-maintainer@vmware.com>,
	"lukasz.spintzyk@displaylink.com"
	<lukasz.spintzyk@displaylink.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>
Subject: RE: [PATCH 01/14] drm: add new plane property FB_DAMAGE_CLIPS to send damage during plane update
Date: Tue, 11 Sep 2018 04:43:02 +0000	[thread overview]
Message-ID: <BYAPR05MB41817153B3FACFD555B8E410BA040@BYAPR05MB4181.namprd05.prod.outlook.com> (raw)
In-Reply-To: <20180907142306.GD5565@intel.com>

> > > > +#include <drm/drmP.h>
> > > > +#include <drm/drm_damage_helper.h>
> > > > +
> > > > +/**
> > > > + * DOC: overview
> > > > + *
> > > > + * FB_DAMAGE_CLIPS is an optional plane property which provides a
> > > means to
> > > > + * specify a list of damage rectangles on a plane in framebuffer
> > > coordinates of
> > > > + * the framebuffer attached to the plane. In current context damage is
> > > the area
> > > > + * of plane framebuffer (excluding the framebuffer area which is outside
> > > of
> > > > + * plane src)
> > >
> > > Not sure why the plane src coordinates need to be mentioned here. The
> > > damage is just the part of the fb that has changed. Whether or not it
> > > extends past the src coordinates is totally irrelevant as far as I can
> > > see.
> >
> > Thanks Ville for the review,
> >
> > Well this is plane damage property and only those clips which falls inside
> > will be used for plane update, so outside plane src is not required.
> 
> Actually we've never specified that properly. My usual interpretation is
> that the plane is allowed to sample past the edge of the src rectangle
> (to get nicer looking edges). But not sure whether that would be too
> surprising to people though. So we might want follow the GL linear filter
> rules by default, and if someone wants better looking edges we could
> add a property that allows the filter to reach further past the edge.

Ok, it makes sense not to specify plane src part, anyway with current
implementation kernel do not error if damage clips are outside plane
src. The helper iterator clip to plane_src but depending on the above
use case can have other implementations as well.

Thanks,
Deepak

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