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To:     Daniel Vetter <daniel@ffwll.ch>,
        Steven Price <steven.price@arm.com>
From:   Chris Wilson <chris@chris-wilson.co.uk>
In-Reply-To: <20190513143921.GP17751@phenom.ffwll.local>
Cc:     Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        David Airlie <airlied@linux.ie>, linux-kernel@vger.kernel.org,
        dri-devel@lists.freedesktop.org,
        Alyssa Rosenzweig <alyssa@rosenzweig.io>
References: <20190513143244.16478-1-steven.price@arm.com>
 <20190513143921.GP17751@phenom.ffwll.local>
Message-ID: <155775884217.2165.11223399053598674062@skylake-alporthouse-com>
User-Agent: alot/0.6
Subject: Re: [PATCH] drm/panfrost: Use drm_gem_dump_map_offset()
Date:   Mon, 13 May 2019 15:47:22 +0100
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Quoting Daniel Vetter (2019-05-13 15:39:21)
> On Mon, May 13, 2019 at 03:32:44PM +0100, Steven Price wrote:
> > panfrost_ioctl_mmap_bo() contains a reimplementation of
> > drm_gem_dump_map_offset() but with a bug - it allows mapping imported
> > objects (without going through the exporter). Fix this by switching to
> > use the generic drm_gem_dump_map_offset() function instead which has the
> > bonus of simplifying the code.
> 
> gem_dumb stuff is for kms drivers, panfrost is a render driver. We're
> generally trying to separate these two worlds somewhat cleanly.
> 
> I think it'd be good to have a non-dumb version of this in the core, and
> use that. Or upgrade the dumb version to be that helper for everyone (and
> drop the _dumb).

More specifically, since panfrost is using the drm_gem_shmem helper and
vm_ops, it too can provide the wrapper as it is the drm_gem_shmem layer
that implies that trying to mmap an imported object is an issue as that
is not a universal problem.
-Chris