Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755800AbaGVPT6 (ORCPT ); Tue, 22 Jul 2014 11:19:58 -0400 Received: from mail-ie0-f173.google.com ([209.85.223.173]:45476 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751449AbaGVPT5 convert rfc822-to-8bit (ORCPT ); Tue, 22 Jul 2014 11:19:57 -0400 MIME-Version: 1.0 X-Originating-IP: [84.73.67.144] In-Reply-To: <53CE77B4.6020801@amd.com> References: <20140709093124.11354.3774.stgit@patser> <20140709122953.11354.46381.stgit@patser> <53CE2421.5040906@amd.com> <20140722114607.GL15237@phenom.ffwll.local> <20140722115737.GN15237@phenom.ffwll.local> <53CE56ED.4040109@vodafone.de> <53CE6FB0.90500@canonical.com> <53CE7410.3090603@amd.com> <53CE74B5.3000201@canonical.com> <53CE77B4.6020801@amd.com> Date: Tue, 22 Jul 2014 17:19:56 +0200 X-Google-Sender-Auth: Q8pdSbxp6cjTx0YpUs7KaqUQedo Message-ID: Subject: Re: [PATCH 09/17] drm/radeon: use common fence implementation for fences From: Daniel Vetter To: =?UTF-8?Q?Christian_K=C3=B6nig?= Cc: Maarten Lankhorst , =?UTF-8?Q?Christian_K=C3=B6nig?= , Dave Airlie , Thomas Hellstrom , nouveau , LKML , dri-devel , Ben Skeggs , "Deucher, Alexander" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 22, 2014 at 4:39 PM, Christian König wrote: > Am 22.07.2014 16:27, schrieb Maarten Lankhorst: > >> op 22-07-14 16:24, Christian König schreef: >>>> >>>> No, you really shouldn't be doing much in the check anyway, it's meant >>>> to be a lightweight check. If you're not ready yet because of a lockup >>>> simply return not signaled yet. >>> >>> It's not only the lockup case from radeon I have in mind here. For >>> userspace queues it might be necessary to call copy_from_user to figure out >>> if a fence is signaled or not. >>> >>> Returning false all the time is probably not a good idea either. >> >> Having userspace implement a fence sounds like an awful idea, why would >> you want to do that? > > > Marketing moves in mysterious ways. Don't ask me, but that the direction it > currently moves with userspace queues and IOMMU etc... Fence-based syncing between userspace queues submitted stuff through doorbells and anything submitted by the general simply wont work. Which is why I think the doorbell is a stupid interface since I just don't see cameras and v4l devices implementing all that complexity to get a pure userspace side sync solution. But that's a different problem really, and I guess marketing will eventually figure this one out, too. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/