From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from osg.samsung.com ([64.30.133.232]:63017 "EHLO osg.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754945AbdKQL5j (ORCPT ); Fri, 17 Nov 2017 06:57:39 -0500 Date: Fri, 17 Nov 2017 09:57:31 -0200 From: Mauro Carvalho Chehab To: Gustavo Padovan 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: <20171117095731.2172c3c2@vento.lan> In-Reply-To: <20171115171057.17340-2-gustavo@padovan.org> References: <20171115171057.17340-1-gustavo@padovan.org> <20171115171057.17340-2-gustavo@padovan.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: 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. Regards, Mauro