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From: Daniel Vetter <daniel@ffwll.ch>
To: Eric Anholt <eric@anholt.net>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/3] drm/vc4: Don't try to initialize FBDEV if we're only bound to V3D.
Date: Wed, 19 Apr 2017 21:36:04 +0200	[thread overview]
Message-ID: <CAKMK7uHBE1Qtjr2dM3U9edEfZ0mXVEjcw+hs8mF9ZkRP4Vcm=A@mail.gmail.com> (raw)
In-Reply-To: <8760i046zw.fsf@eliezer.anholt.net>

On Wed, Apr 19, 2017 at 7:55 PM, Eric Anholt <eric@anholt.net> wrote:
> Daniel Vetter <daniel@ffwll.ch> writes:
>> On Tue, Apr 18, 2017 at 9:11 PM, Eric Anholt <eric@anholt.net> wrote:
>>> The FBDEV initialization would throw an error in dmesg, when we just
>>> want to silently not initialize fbdev on a V3D-only VC4 instance.
>>>
>>> Signed-off-by: Eric Anholt <eric@anholt.net>
>>
>> Hm, this shouldn't be an error really, you might want to hotplug more
>> connectors later on. What exactly complains?
>
> drm_fb_helper_init() throws an error if the passed in connector count is
> 0, so drm_fb_cma_helper() printks an error.

Oh, _that_ thing. The error in there is correct, but (almost) everyone
gets this parameter wrong. This isn't the max number of connectors the
fb helper will light up, but just the max number of connectors _per_
crtc when driving in hw clone mode. There's two problems with that:
- fb helpers don't support hw clone mode, we select 1:1 crtcs for each
active connector
- I mentioned that everyone gets this wrong?

If you're moderately bored it'd be great to nuke the max_connector
argument from drm_fb_helper_init, and hard-code it to 1 (with a big
comment explaining that this needs to be changed, probably with
dynamic reallocation, once someone gets around to implementing hw
clone mode).

If you're less bored, just hardcode this to 1 in vc4 and done. Plus a
TODO.rst entry would be great in that case.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

  reply	other threads:[~2017-04-19 19:36 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-18 19:11 [PATCH 1/3] drm/vc4: Turn the V3D clock on at runtime Eric Anholt
2017-04-18 19:11 ` [PATCH 2/3] drm/vc4: Don't try to initialize FBDEV if we're only bound to V3D Eric Anholt
2017-04-19  4:59   ` Daniel Vetter
2017-04-19 17:55     ` Eric Anholt
2017-04-19 19:36       ` Daniel Vetter [this message]
2017-04-21 22:53         ` Eric Anholt
2017-04-24 14:26           ` Alex Deucher
2017-05-02  8:16             ` Daniel Vetter
2017-04-18 19:11 ` [PATCH 3/3] drm/vc4: Add specific compatible strings for Cygnus Eric Anholt
2017-04-20 20:33   ` Rob Herring
2017-04-18 19:23 ` [PATCH 1/3] drm/vc4: Turn the V3D clock on at runtime Eric Anholt
2017-04-18 23:38 ` [PATCH 1/3 v2] " Eric Anholt
2017-04-18 23:48   ` Florian Fainelli
2017-04-19  0:02     ` Eric Anholt
2017-04-19  0:02     ` Eric Anholt
2017-04-24 20:12     ` [PATCH 1/3 v3] " Eric Anholt
2017-04-28 18:29       ` Rob Herring
2017-04-28 21:41         ` Eric Anholt

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