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