From mboxrd@z Thu Jan 1 00:00:00 1970 From: mchehab@s-opensource.com (Mauro Carvalho Chehab) Date: Fri, 17 Mar 2017 14:49:27 -0300 Subject: [PATCH v4 14/36] [media] v4l2-mc: add a function to inherit controls from a pipeline In-Reply-To: <20170317121608.GE21222@n2100.armlinux.org.uk> References: <20170310140124.GV21222@n2100.armlinux.org.uk> <20170310125342.7f047acf@vento.lan> <20170310223714.GI3220@valkosipuli.retiisi.org.uk> <20170311082549.576531d0@vento.lan> <20170313124621.GA10701@valkosipuli.retiisi.org.uk> <20170314004533.3b3cd44b@vento.lan> <20170317114203.GZ21222@n2100.armlinux.org.uk> <1489752127.2905.49.camel@pengutronix.de> <20170317121608.GE21222@n2100.armlinux.org.uk> Message-ID: <20170317144927.1298d5b3@vento.lan> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Em Fri, 17 Mar 2017 12:16:08 +0000 Russell King - ARM Linux escreveu: > On Fri, Mar 17, 2017 at 01:02:07PM +0100, Philipp Zabel wrote: > > I think most of the simple, fixed pipeline use cases could be handled by > > libv4l2, by allowing to pass a v4l2 subdevice path to v4l2_open. If that > > function internally would set up the media links to the > > nearest /dev/video interface, propagate format, resolution and frame > > intervals if necessary, and return an fd to the video device, there'd be > > no additional complexity for the users beyond selecting the v4l2_subdev > > instead of the video device. > > ... which would then require gstreamer to be modified too. The gstreamer > v4l2 plugin looks for /dev/video* or /dev/v4l2/video* devices and monitors > these for changes, so gstreamer applications know which capture devices > are available: > > const gchar *paths[] = { "/dev", "/dev/v4l2", NULL }; > const gchar *names[] = { "video", NULL }; > > /* Add some depedency, so the dynamic features get updated upon changes in > * /dev/video* */ > gst_plugin_add_dependency (plugin, > NULL, paths, names, GST_PLUGIN_DEPENDENCY_FLAG_FILE_NAME_IS_PREFIX); > > I haven't checked yet whether sys/v4l2/gstv4l2deviceprovider.c knows > anything about the v4l2 subdevs. Not only gstreamer do that, but all simple V4L2 applications, although on most of them, you can either pass a command line argument or setup the patch via GUI. Btw, I've no idea from where gstreamer took /dev/v4l2 :-) I'm yet to find a distribution using it. On the other hand, /dev/v4l/by-patch and /dev/v4l/by-id are usual directories where V4L2 devices can be found, and should provide persistent names. So, IMHO, gst should prefer those names, when they exist: $ tree /dev/v4l /dev/v4l ??? by-id ??? ??? usb-046d_HD_Pro_Webcam_C920_55DA1CCF-video-index0 -> ../../video1 ??? ??? usb-Sunplus_mMobile_Inc_USB_Web-CAM-video-index0 -> ../../video0 ??? by-path ??? platform-3f980000.usb-usb-0:1.2:1.0-video-index0 -> ../../video1 ??? platform-3f980000.usb-usb-0:1.5:1.0-video-index0 -> ../../video0 Thanks, Mauro