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From:   Emil Velikov <emil.l.velikov@gmail.com>
Date:   Fri, 3 Aug 2018 13:35:41 +0100
Message-ID: <CACvgo53h=8q-xuJBPP1T2JWkb7SffXas94=moS1x76=BejyVJA@mail.gmail.com>
Subject: Re: [RFC] drm: Allow DRM_IOCTL_MODE_MAP_DUMB for render nodes
To:     Martin Fuzzey <martin.fuzzey@flowbird.group>
Cc:     Robert Foss <robert.foss@collabora.com>,
        David Airlie <airlied@linux.ie>,
        Brian Paul <brianp@vmware.com>,
        ML dri-devel <dri-devel@lists.freedesktop.org>,
        Eric Engestrom <eric.engestrom@intel.com>,
        Gustavo Padovan <gustavo@padovan.org>,
        "Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Nicolas Norvez <norvez@chromium.org>,
        Rob Herring <robh@kernel.org>,
        Sean Paul <seanpaul@chromium.org>,
        Tomasz Figa <tfiga@chromium.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>
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Hi Martin,

On 1 August 2018 at 15:24, Martin Fuzzey <martin.fuzzey@flowbird.group> wrote:
> Hi,
>
> I am running into the same problem using etnaviv on i.MX6 under Android 8.1
>
> The mesa etnaviv code uses CREATE_DUMB / MAP_DUMB for the scanout buffers
> and is called from the surfaceflinger process.
>
> But, under Android 8.1 drm_hwcomposer runs in a seperate process to
> surfaceflinger.
> Since drm_hwcomposer needs to use the KMS API it must be the DRM master,
> that means that surface flinger cannot be DRM master too.
>
> Adding a render node to the imx drm device and configuring mesa to user
> fixes
> the problem but requires the render node to have access rights to use
> CREATE_DUMB
> / MAP_DUMB.
>
>
> Here is my full patch:
>
> Make imx-drm export a render node so that mesa can use it to allocate
>
Let's start with the not-so obvious question:
Why does one open the imx as render node?

Of the top of my head:
There is nothing in egl/android that should require an authenticated device.
Hence, using a card node should be fine - the etnaviv code opens the
render node it needs.

It's been a while since I looked at the imx/etna code, so I may be
missing something.

HTH
Emil