Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1428126AbdDXO1V (ORCPT ); Mon, 24 Apr 2017 10:27:21 -0400 Received: from mail-yw0-f194.google.com ([209.85.161.194]:33029 "EHLO mail-yw0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1172584AbdDXO0r (ORCPT ); Mon, 24 Apr 2017 10:26:47 -0400 MIME-Version: 1.0 In-Reply-To: <87wpadtlsl.fsf@eliezer.anholt.net> References: <20170418191157.18517-1-eric@anholt.net> <20170418191157.18517-2-eric@anholt.net> <8760i046zw.fsf@eliezer.anholt.net> <87wpadtlsl.fsf@eliezer.anholt.net> From: Alex Deucher Date: Mon, 24 Apr 2017 10:26:45 -0400 Message-ID: Subject: Re: [PATCH 2/3] drm/vc4: Don't try to initialize FBDEV if we're only bound to V3D. To: Eric Anholt Cc: Daniel Vetter , Mark Rutland , "devicetree@vger.kernel.org" , Rob Herring , Linux Kernel Mailing List , dri-devel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1816 Lines: 40 On Fri, Apr 21, 2017 at 6:53 PM, Eric Anholt wrote: > Daniel Vetter writes: > >> On Wed, Apr 19, 2017 at 7:55 PM, Eric Anholt wrote: >>> Daniel Vetter writes: >>>> On Tue, Apr 18, 2017 at 9:11 PM, Eric Anholt 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 >>>> >>>> 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. > > If I'm driving a GPU with no display subsystem at all, it seems like I > shouldn't initialize fbdev for it, right? That's what we do for radeon/amdgpu on hw without display blocks. Alex