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trumee
Guru
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Joined: 02 Mar 2003
Posts: 461
Location: London,UK

PostPosted: Fri Aug 09, 2013 10:00 pm    Post subject: udev rule webcam Reply with quote

Hi,

My laptop has an inbuilt webcam which points to /dev/video0, and an usb logitech webcam which appears at /dev/video1. I would like my logitech webcam to be at /dev/video5. Unfortunatelt, it didnt work as following messages show. any idea why?

Code:

#lsusb
Bus 002 Device 014: ID 046d:081d Logitech, Inc. HD Webcam C510


Code:

cat /etc/udev/rules.d/99-local.rules

KERNEL=="video[0-9]*", SUBSYSTEM=="video4linux", ENV{ID_V4L_PRODUCT}=="UVC Camera (046d:081d)", NAME="video5", GROUP="video", OPTIONS="last_rule"


On plugging the webcam
Code:

udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

KERNEL[5304.549787] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2 (usb)
KERNEL[5304.549846] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0 (usb)
KERNEL[5304.549885] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.1 (usb)
KERNEL[5304.549908] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2 (usb)
KERNEL[5304.796437] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2/video4linux/video1 (video4linux)
KERNEL[5304.796493] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2/input/input19 (input)
KERNEL[5304.796514] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2/input/input19/event10 (input)
KERNEL[5304.796561] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.3 (usb)
UDEV  [5304.796876] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2 (usb)
UDEV  [5304.797284] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0 (usb)
UDEV  [5304.797745] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2 (usb)
UDEV  [5304.797769] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.3 (usb)
UDEV  [5304.797781] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.1 (usb)
UDEV  [5304.798497] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2/input/input19 (input)
UDEV  [5304.799113] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2/input/input19/event10 (input)
UDEV  [5304.801067] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.2/video4linux/video1 (video4linux)


Finally
Code:

#ls /dev/video*

/dev/video0  /dev/video1


/dev/video5 is never created!
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quilosaq
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Joined: 22 Dec 2009
Posts: 763

PostPosted: Fri Aug 09, 2013 11:44 pm    Post subject: Re: udev rule webcam Reply with quote

trumee wrote:
...
Code:

cat /etc/udev/rules.d/99-local.rules

KERNEL=="video[0-9]*", SUBSYSTEM=="video4linux", ENV{ID_V4L_PRODUCT}=="UVC Camera (046d:081d)", NAME="video5", GROUP="video", OPTIONS="last_rule"

...

You can't use NAME="foo" for naming your webcam. NAME is reserved for network interface names. Use this rule:
Code:
KERNEL=="video[0-9]*", SUBSYSTEM=="video4linux", ENV{ID_V4L_PRODUCT}=="UVC Camera (046d:081d)", SYMLINK+="video5", GROUP="video", OPTIONS="last_rule"

If it does work, try:
Code:
ACTION=="add", KERNEL=="video1", SUBSYSTEM=="video4linux", SYMLINK+="video5", GROUP="video", OPTIONS="last_rule"
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trumee
Guru
Guru


Joined: 02 Mar 2003
Posts: 461
Location: London,UK

PostPosted: Sat Aug 10, 2013 5:50 am    Post subject: Re: udev rule webcam Reply with quote

quilosaq wrote:


You can't use NAME="foo" for naming your webcam. NAME is reserved for network interface names. Use this rule:
Code:
KERNEL=="video[0-9]*", SUBSYSTEM=="video4linux", ENV{ID_V4L_PRODUCT}=="UVC Camera (046d:081d)", SYMLINK+="video5", GROUP="video", OPTIONS="last_rule"

If it does work, try:
Code:
ACTION=="add", KERNEL=="video1", SUBSYSTEM=="video4linux", SYMLINK+="video5", GROUP="video", OPTIONS="last_rule"


Thanks, this did work. It created a /dev/video1 and a symlink /dev/video5.
Code:


# ls -la /dev/video*
crw-rw---- 1 root video 81, 0 Aug 10 06:44 /dev/video0
crw-rw---- 1 root video 81, 1 Aug 10 06:46 /dev/video1
lrwxrwxrwx 1 root root      6 Aug 10 06:46 /dev/video5 -> video1


Is it possible not to have /dev/video1 at all, and rather than symlink have a webcam directly addressable at /dev/video5?
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PaulBredbury
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Joined: 14 Jul 2005
Posts: 7310

PostPosted: Sat Aug 10, 2013 7:12 am    Post subject: Reply with quote

Why your attachment to "video5"? That's a name to be avoided, e.g. this situation:

You plug in 5 webcams
Then you plug in the webcam that becomes video5, so where does the previous video5 go?

You're supposed to use a symlink that uses a different naming convention, e.g. "mycam" or whatever. Anything but "video$n".
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