From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755502AbdKQMXX (ORCPT ); Fri, 17 Nov 2017 07:23:23 -0500 Received: from mail-qt0-f195.google.com ([209.85.216.195]:36471 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751950AbdKQMXN (ORCPT ); Fri, 17 Nov 2017 07:23:13 -0500 X-Google-Smtp-Source: AGs4zMZyQMv1YUXVZEGy1DMftxvspJVC+yzsd2JTmua2fjDAwAaAqP3/ZhTwG14zua1Skr5M0Ww0NA== Date: Fri, 17 Nov 2017 10:23:05 -0200 From: Gustavo Padovan To: Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org, Hans Verkuil , Shuah Khan , Pawel Osciak , Alexandre Courbot , Sakari Ailus , Brian Starkey , Thierry Escande , linux-kernel@vger.kernel.org, Gustavo Padovan Subject: Re: [RFC v5 01/11] [media] v4l: add V4L2_CAP_ORDERED to the uapi Message-ID: <20171117122305.GE19033@jade> References: <20171115171057.17340-1-gustavo@padovan.org> <20171115171057.17340-2-gustavo@padovan.org> <20171117095731.2172c3c2@vento.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171117095731.2172c3c2@vento.lan> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2017-11-17 Mauro Carvalho Chehab : > Em Wed, 15 Nov 2017 15:10:47 -0200 > Gustavo Padovan escreveu: > > > From: Gustavo Padovan > > > > When using explicit synchronization userspace needs to know if > > the queue can deliver everything back in the same order, so we added > > a new capability that drivers can use to report that they are capable > > of keeping ordering. > > > > In videobuf2 core when using fences we also make sure to keep the ordering > > of buffers, so if the driver guarantees it too the whole pipeline inside > > V4L2 will be ordered and the V4L2_CAP_ORDERED should be used. > > > > Signed-off-by: Gustavo Padovan > > --- > > Documentation/media/uapi/v4l/vidioc-querycap.rst | 3 +++ > > include/uapi/linux/videodev2.h | 1 + > > 2 files changed, 4 insertions(+) > > > > diff --git a/Documentation/media/uapi/v4l/vidioc-querycap.rst b/Documentation/media/uapi/v4l/vidioc-querycap.rst > > index 66fb1b3d6e6e..ed3daa814da9 100644 > > --- a/Documentation/media/uapi/v4l/vidioc-querycap.rst > > +++ b/Documentation/media/uapi/v4l/vidioc-querycap.rst > > @@ -254,6 +254,9 @@ specification the ioctl returns an ``EINVAL`` error code. > > * - ``V4L2_CAP_TOUCH`` > > - 0x10000000 > > - This is a touch device. > > + * - ``V4L2_CAP_ORDERED`` > > + - 0x20000000 > > + - The device queue is ordered. > > * - ``V4L2_CAP_DEVICE_CAPS`` > > - 0x80000000 > > - The driver fills the ``device_caps`` field. This capability can > > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > > index 185d6a0acc06..cd6fc1387f47 100644 > > --- a/include/uapi/linux/videodev2.h > > +++ b/include/uapi/linux/videodev2.h > > @@ -459,6 +459,7 @@ struct v4l2_capability { > > #define V4L2_CAP_STREAMING 0x04000000 /* streaming I/O ioctls */ > > > > #define V4L2_CAP_TOUCH 0x10000000 /* Is a touch device */ > > +#define V4L2_CAP_ORDERED 0x20000000 /* Is the device queue ordered */ > > I guess we discussed that at the Linux Media summit. > The problem of making it a global flag is that drivers may support > ordered formats only for some of the formats. E. g., a driver that > delivers both MPEG and RGB output formats may deliver ordered > buffers for RGB, and unordered ones for MPEG. > > So, instead of doing a global format at v4l2_capability, it is probably > better to use the flags field at struct v4l2_fmtdesc. > > That would allow userspace to know in advance what formats support > it, by calling VIDIOC_ENUM_FMT. Thanks for clarifying, Mauro. I'll work on making it part of v4l2_fmtdesc. Gustavo