Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755330AbdHYKGn (ORCPT ); Fri, 25 Aug 2017 06:06:43 -0400 Received: from ec2-52-27-115-49.us-west-2.compute.amazonaws.com ([52.27.115.49]:49565 "EHLO osg.samsung.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754850AbdHYKGm (ORCPT ); Fri, 25 Aug 2017 06:06:42 -0400 Date: Fri, 25 Aug 2017 07:06:32 -0300 From: Mauro Carvalho Chehab To: Hans Verkuil Cc: Linux Doc Mailing List , Linux Media Mailing List , Mauro Carvalho Chehab , Mauro Carvalho Chehab , linux-kernel@vger.kernel.org, Jonathan Corbet , Laurent Pinchart , Sakari Ailus , Hans Verkuil Subject: Re: [PATCH 2/3] media: videodev2: add a flag for vdev-centric devices Message-ID: <20170825070632.28580858@vento.lan> In-Reply-To: <4f771cfa-0e0d-3548-a363-6470b32a6634@cisco.com> References: <8d504be517755ee9449a007b5f2de52738c2df63.1503653839.git.mchehab@s-opensource.com> <4f771cfa-0e0d-3548-a363-6470b32a6634@cisco.com> Organization: Samsung X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4183 Lines: 107 Em Fri, 25 Aug 2017 11:44:27 +0200 Hans Verkuil escreveu: > On 08/25/2017 11:40 AM, Mauro Carvalho Chehab wrote: > > From: Mauro Carvalho Chehab > > > > As both vdev-centric and mc-centric devices may implement the > > same APIs, we need a flag to allow userspace to distinguish > > between them. > > > > Signed-off-by: Mauro Carvalho Chehab > > Signed-off-by: Mauro Carvalho Chehab > > --- > > Documentation/media/uapi/v4l/open.rst | 6 ++++++ > > Documentation/media/uapi/v4l/vidioc-querycap.rst | 4 ++++ > > include/uapi/linux/videodev2.h | 2 ++ > > 3 files changed, 12 insertions(+) > > > > diff --git a/Documentation/media/uapi/v4l/open.rst b/Documentation/media/uapi/v4l/open.rst > > index a72d142897c0..eb3f0ec57edb 100644 > > --- a/Documentation/media/uapi/v4l/open.rst > > +++ b/Documentation/media/uapi/v4l/open.rst > > @@ -33,6 +33,12 @@ For **vdev-centric** control, the device and their corresponding hardware > > pipelines are controlled via the **V4L2 device** node. They may optionally > > expose via the :ref:`media controller API `. > > > > +.. note:: > > + > > + **vdev-centric** devices should report V4L2_VDEV_CENTERED > > You mean CENTRIC, not CENTERED. Yeah, true. I'll fix it. > But I would change this to MC_CENTRIC: the vast majority of drivers are VDEV centric, > so it makes a lot more sense to keep that as the default and only set the cap for > MC-centric drivers. I actually focused it on what an userspace application would do. An specialized application for a given hardware will likely just ignore whatever flag is added, and use vdev, mc and subdev APIs as it pleases. So, those applications don't need any flag at all. However, a generic application needs a flag to allow them to check if a given hardware can be controlled by the traditional way to control the device (e. g. if it accepts vdev-centric type of hardware control). It is an old desire (since when MC was designed) to allow that generic V4L2 apps to also work with MC-centric hardware somehow. At the moment we add that (either in Kernelspace, as proposed for iMX6 [1] or via libv4l), a mc-centric hardware can also be vdev-centric. [1] one alternative proposed for iMX6 driver, would be to enable vdev-centric control only for hardware with a single camera slot, like those cheap RPi3-camera compatible hardware, by using some info at the DT. > > Regards, > > Hans > > > + :c:type:`v4l2_capability` flag (see :ref:`VIDIOC_QUERYCAP`). > > + > > + > > For **MC-centric** control, before using the V4L2 device, it is required to > > set the hardware pipelines via the > > :ref:`media controller API `. For those devices, the > > diff --git a/Documentation/media/uapi/v4l/vidioc-querycap.rst b/Documentation/media/uapi/v4l/vidioc-querycap.rst > > index 12e0d9a63cd8..4856821b7608 100644 > > --- a/Documentation/media/uapi/v4l/vidioc-querycap.rst > > +++ b/Documentation/media/uapi/v4l/vidioc-querycap.rst > > @@ -252,6 +252,10 @@ specification the ioctl returns an ``EINVAL`` error code. > > * - ``V4L2_CAP_TOUCH`` > > - 0x10000000 > > - This is a touch device. > > + * - ``V4L2_VDEV_CENTERED`` > > + - 0x20000000 > > + - This is controlled via V4L2 device nodes (radio, video, vbi, > > + sdr > > * - ``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 45cf7359822c..d89090d99042 100644 > > --- a/include/uapi/linux/videodev2.h > > +++ b/include/uapi/linux/videodev2.h > > @@ -460,6 +460,8 @@ struct v4l2_capability { > > > > #define V4L2_CAP_TOUCH 0x10000000 /* Is a touch device */ > > > > +#define V4L2_CAP_VDEV_CENTERED 0x20000000 /* V4L2 Device is controlled via V4L2 device devnode */ > > + > > #define V4L2_CAP_DEVICE_CAPS 0x80000000 /* sets device capabilities field */ > > > > /* > > > Thanks, Mauro