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

On Tue, Oct 30, 2018 at 11:28:24AM +0200, Jani Nikula wrote:

On Tue, 30 Oct 2018, Daniel Vetter [off-list ref] wrote:

quoted

On Mon, Oct 29, 2018 at 09:05:20PM +0100, Gerd Hoffmann wrote:

quoted

On Mon, Oct 29, 2018 at 07:44:28PM +0200, Jani Nikula wrote:

quoted

On Mon, 29 Oct 2018, Gerd Hoffmann [off-list ref] wrote:

quoted

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.

But nowadays we do handle the debugfs EDID override and the EDID
firmware loading in drm_do_get_edid(), so using that gives you those
features.

Oh, missed that. Would be good to clarify the kernel doc and mention this
in e.g. both drm_add_edid_modes() and &drm_connector_helper_funcs.get_modes?

And maybe make it more obvious that drm_do_get_edid is also for virtual
drivers, atm the kerneldoc talks a lot about DDC and everything hw.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch