linux-kernel - Re: [PATCH v3] drm/bochs: add edid support.

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Message-ID: <20181030090632.GJ21967@phenom.ffwll.local>
Date:   Tue, 30 Oct 2018 10:06:32 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        David Airlie <airlied@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org,
        "open list:DRM DRIVER FOR BOCHS VIRTUAL GPU" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v3] drm/bochs: add edid support.

On Mon, Oct 29, 2018 at 09:05:20PM +0100, Gerd Hoffmann wrote:
> On Mon, Oct 29, 2018 at 07:44:28PM +0200, Jani Nikula wrote:
> > On Mon, 29 Oct 2018, Gerd Hoffmann <kraxel@...hat.com> wrote:
> > > Recent qemu (latest master branch, upcoming 3.1 release) got support
> > > for EDID data.  This patch adds guest driver support.
> > >
> > > EDID support in qemu is not (yet) enabled by default, so please use
> > > 'qemu -device VGA,edid=on' for testing.
> > 
> > Any chance of making this use drm_get_edid() (requires an i2c_adapter)
> > or at least drm_do_get_edid()?
> 
> I'll have a look at using drm_do_get_edid().  drm_get_edid() will not
> fly as there is no i2c adapter in the first place.

Hm, not sure that makes sense. drm_do_get_edid is to handle the real-world
flakiness of sinks (it's where all the retry logic resides), if you don't
have a i2c_adapater (because the hw has some magic "give me an edid"
block). For virtual hw we hopefully don't randomly drop bits on the floor
between the guest and host. Imo totally fine as-is.

E.g. we also don't feed the VBT edid through drm_do_get_edid either.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch