From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751658AbdJBNnz (ORCPT ); Mon, 2 Oct 2017 09:43:55 -0400 Received: from foss.arm.com ([217.140.101.70]:37214 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750957AbdJBNnx (ORCPT ); Mon, 2 Oct 2017 09:43:53 -0400 Date: Mon, 2 Oct 2017 14:43:50 +0100 From: Brian Starkey To: Gustavo Padovan Cc: linux-media@vger.kernel.org, Hans Verkuil , Mauro Carvalho Chehab , Shuah Khan , linux-kernel@vger.kernel.org, Gustavo Padovan , Jonathan.Chai@arm.com Subject: Re: [PATCH v3 10/15] [media] vb2: add 'ordered' property to queues Message-ID: <20171002134350.GE22538@e107564-lin.cambridge.arm.com> References: <20170907184226.27482-1-gustavo@padovan.org> <20170907184226.27482-11-gustavo@padovan.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20170907184226.27482-11-gustavo@padovan.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Thu, Sep 07, 2017 at 03:42:21PM -0300, Gustavo Padovan wrote: >From: Gustavo Padovan > >For explicit synchronization (and soon for HAL3/Request API) we need >the v4l2-driver to guarantee the ordering in which the buffers were queued >by userspace. This is already true for many drivers, but we never needed >to say it. > >Signed-off-by: Gustavo Padovan >--- > include/media/videobuf2-core.h | 4 ++++ > 1 file changed, 4 insertions(+) > >diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h >index 5ed8d3402474..20099dc22f26 100644 >--- a/include/media/videobuf2-core.h >+++ b/include/media/videobuf2-core.h >@@ -508,6 +508,9 @@ struct vb2_buf_ops { > * @last_buffer_dequeued: used in poll() and DQBUF to immediately return if the > * last decoded buffer was already dequeued. Set for capture queues > * when a buffer with the V4L2_BUF_FLAG_LAST is dequeued. >+ * @ordered: if the driver can guarantee that the queue will be ordered or not. >+ * The default is not ordered unless the driver sets this flag. It >+ * is mandatory for using explicit fences. If it's mandatory for fences (why is that?), then I guess this patch should come before any of the fence implementation? But it's not entirely clear to me what this flag means - ordered with respect to what? Ordered such that the order in which the buffers are queued in the driver are the same order that they will be dequeued by userspace? I think the order they are queued from userspace can still be different from both the order they are queued in the driver (because the in-fences can signal in any order), and dequeued again in userspace, so "ordered" seems a bit ambiguous. I think it should be more clear. Cheers -Brian > * @fileio: file io emulator internal data, used only if emulator is active > * @threadio: thread io internal data, used only if thread is active > */ >@@ -560,6 +563,7 @@ struct vb2_queue { > unsigned int is_output:1; > unsigned int copy_timestamp:1; > unsigned int last_buffer_dequeued:1; >+ unsigned int ordered:1; > > struct vb2_fileio_data *fileio; > struct vb2_threadio_data *threadio; >-- >2.13.5 >