Re: [PATCH v5 00/39] i.MX Media Driver

[Steve Longerbeam]

On 03/12/2017 03:10 PM, Mauro Carvalho Chehab wrote:
> Em Sun, 12 Mar 2017 21:13:24 +0000
> Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx> escreveu:
>
> > On Sun, Mar 12, 2017 at 05:59:28PM -0300, Mauro Carvalho Chehab wrote:
> > > Yet, udev/systemd has some rules that provide an unique name for V4L
> > > devices at /lib/udev/rules.d/60-persistent-v4l.rules. Basically, it
> > > runs a small application (v4l_id) with creates a persistent symling
> > > using rules like this:
> > >
> > > 	KERNEL=="video*", ENV{ID_SERIAL}=="?*", SYMLINK+="v4l/by-id/$env{ID_BUS}-$env{ID_SERIAL}-video-index$attr{index}"
> > >
> > > Those names are stored at /dev/v4l/by-path.
> > This doesn't help:
> >
> > $ ls -Al /dev/v4l/by-id/
> > total 0
> > lrwxrwxrwx 1 root root 13 Mar 12 19:54 usb-Sonix_Technology_Co.__Ltd._USB_2.0_Camera-video-index0 -> ../../video10
> > $ ls -Al /dev/v4l/by-path/
> > total 0
> > lrwxrwxrwx 1 root root 12 Mar 12 19:54 platform-2040000.vpu-video-index0 -> ../../video0
> > lrwxrwxrwx 1 root root 12 Mar 12 19:54 platform-2040000.vpu-video-index1 -> ../../video1
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index0 -> ../../video2
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index1 -> ../../video3
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index2 -> ../../video4
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index3 -> ../../video5
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index4 -> ../../video6
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index5 -> ../../video7
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index6 -> ../../video8
> > lrwxrwxrwx 1 root root 12 Mar 12 20:53 platform-capture-subsystem-video-index7 -> ../../video9
> > lrwxrwxrwx 1 root root 13 Mar 12 19:54 platform-ci_hdrc.0-usb-0:1:1.0-video-index0 -> ../../video10
> >
> > The problem is the "platform-capture-subsystem-video-index" entries.
> > These themselves change order.  For instance, I now have:
> >
> > - entity 72: ipu1_csi0 capture (1 pad, 1 link)
> >               type Node subtype V4L flags 0
> >               device node name /dev/video6
> >
> > which means it's platform-capture-subsystem-video-index4.  Before, it
> > was platform-capture-subsystem-video-index2.
> That's a driver problem. v4l_id gets information to build the persistent
> name from the result of VIDIOC_QUERYCAP.
>
> In the case of Exynos gsc driver, for example, the information is here:
>
> static int gsc_m2m_querycap(struct file *file, void *fh,
> 			   struct v4l2_capability *cap)
> {
> 	struct gsc_ctx *ctx = fh_to_ctx(fh);
> 	struct gsc_dev *gsc = ctx->gsc_dev;
>
> 	strlcpy(cap->driver, GSC_MODULE_NAME, sizeof(cap->driver));
> 	strlcpy(cap->card, GSC_MODULE_NAME " gscaler", sizeof(cap->card));
> 	snprintf(cap->bus_info, sizeof(cap->bus_info), "platform:%s",
> 		 dev_name(&gsc->pdev->dev));
> 	cap->device_caps = V4L2_CAP_STREAMING | V4L2_CAP_VIDEO_M2M_MPLANE |
> 		V4L2_CAP_VIDEO_CAPTURE_MPLANE |	V4L2_CAP_VIDEO_OUTPUT_MPLANE;
>
> 	cap->capabilities = cap->device_caps | V4L2_CAP_DEVICE_CAPS;
> 	return 0;
> }
>
> See that the bus_info there is filled with:
>
> 	snprintf(cap->bus_info, sizeof(cap->bus_info), "platform:%s", dev_name(&gsc->pdev->dev));
>
>  From the output you printed, it seems that the i.MX6 is just doing:
> 	snprintf(cap->bus_info, sizeof(cap->bus_info), "platform:");
> for some devices.

imx6 is setting bus_info string on all capture devices as:

snprintf(cap->bus_info, sizeof(cap->bus_info),
                 "platform:%s", dev_name(priv->dev));

dev_name(priv->dev) is the device name of the attached subdev.
So the bus_info string, at least for attached CSI subdevs, should
be "platform:imx-ipuv3-csi".

Maybe there is something else missing, I haven't had a chance to
look at this yet.

Steve


> If you change the i.MX6 driver to do the same, you'll likely be able to
> have unique names there too.
>
> Regards,
> Mauro