Discussion:
[linux-uvc-devel] Logitech C270 cannot open /dev/video0
Marian Mihailescu
2015-06-14 03:34:13 UTC
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I am trying to install a webcam on a Synology NAS (arm, linux kernel
3.2.40). I have compiled and installed the kernel modules, this is the
kernel output when inserting the modules and plugging the camera
(Logitech C270):

[ 130.963903] Linux video capture interface: v2.00
[ 136.098356] usbcore: registered new interface driver uvcvideo
[ 136.104135] USB Video Class driver (1.1.1)
[ 145.384393] usb 3-2: new high-speed USB device number 4 using
etxhci_hcd_150119
[ 145.628583] uvcvideo: Found UVC 1.00 device USBDevice (046d:0825)
[ 145.726156] input: USBDevice as
/devices/pci0000:00/0000:00:00.0/usb3/3-2/3-2:1.0/input/input0

This is the log when enabling extra debug information:

[ 887.443999] usb 3-2: new high-speed USB device number 5 using
etxhci_hcd_150119
[ 887.688647] uvcvideo: Probing generic UVC device 2
[ 887.688680] uvcvideo: Found format YUV 4:2:2 (YUYV).
[ 887.688691] uvcvideo: - 640x480 (30.0 fps)
[ 887.688698] uvcvideo: - 160x120 (30.0 fps)
[ 887.688705] uvcvideo: - 176x144 (30.0 fps)
[ 887.688711] uvcvideo: - 320x176 (30.0 fps)
[ 887.688718] uvcvideo: - 320x240 (30.0 fps)
[ 887.688724] uvcvideo: - 352x288 (30.0 fps)
[ 887.688731] uvcvideo: - 432x240 (30.0 fps)
[ 887.688737] uvcvideo: - 544x288 (30.0 fps)
[ 887.688744] uvcvideo: - 640x360 (30.0 fps)
[ 887.688750] uvcvideo: - 752x416 (25.0 fps)
[ 887.688756] uvcvideo: - 800x448 (20.0 fps)
[ 887.688763] uvcvideo: - 800x600 (20.0 fps)
[ 887.688769] uvcvideo: - 864x480 (20.0 fps)
[ 887.688776] uvcvideo: - 960x544 (15.0 fps)
[ 887.688782] uvcvideo: - 960x720 (10.0 fps)
[ 887.688789] uvcvideo: - 1024x576 (10.0 fps)
[ 887.688795] uvcvideo: - 1184x656 (10.0 fps)
[ 887.688802] uvcvideo: - 1280x720 (5.0 fps)
[ 887.688808] uvcvideo: - 1280x960 (5.0 fps)
[ 887.688814] uvcvideo: Found format MJPEG.
[ 887.688821] uvcvideo: - 640x480 (30.0 fps)
[ 887.688827] uvcvideo: - 160x120 (30.0 fps)
[ 887.688834] uvcvideo: - 176x144 (30.0 fps)
[ 887.688840] uvcvideo: - 320x176 (30.0 fps)
[ 887.688847] uvcvideo: - 320x240 (30.0 fps)
[ 887.688853] uvcvideo: - 352x288 (30.0 fps)
[ 887.688859] uvcvideo: - 432x240 (30.0 fps)
[ 887.688866] uvcvideo: - 544x288 (30.0 fps)
[ 887.688872] uvcvideo: - 640x360 (30.0 fps)
[ 887.688879] uvcvideo: - 752x416 (30.0 fps)
[ 887.688885] uvcvideo: - 800x448 (30.0 fps)
[ 887.688892] uvcvideo: - 800x600 (30.0 fps)
[ 887.688898] uvcvideo: - 864x480 (30.0 fps)
[ 887.688905] uvcvideo: - 960x544 (30.0 fps)
[ 887.688911] uvcvideo: - 960x720 (30.0 fps)
[ 887.688918] uvcvideo: - 1024x576 (30.0 fps)
[ 887.688924] uvcvideo: - 1184x656 (30.0 fps)
[ 887.688931] uvcvideo: - 1280x720 (30.0 fps)
[ 887.688937] uvcvideo: - 1280x960 (30.0 fps)
[ 887.688961] uvcvideo: Found a Status endpoint (addr 87).
[ 887.688969] uvcvideo: Found UVC 1.00 device USBDevice (046d:0825)
[ 887.695139] uvcvideo: Added control
00000000-0000-0000-0000-000000000001/2 to device 2 entity 1
[ 887.695154] uvcvideo: Adding mapping 'Exposure, Auto' to control
00000000-0000-0000-0000-000000000001/2.
[ 887.695171] uvcvideo: Added control
00000000-0000-0000-0000-000000000001/3 to device 2 entity 1
[ 887.695183] uvcvideo: Adding mapping 'Exposure, Auto Priority' to
control 00000000-0000-0000-0000-000000000001/3.
[ 887.695198] uvcvideo: Added control
00000000-0000-0000-0000-000000000001/4 to device 2 entity 1
[ 887.695209] uvcvideo: Adding mapping 'Exposure (Absolute)' to
control 00000000-0000-0000-0000-000000000001/4.
[ 887.695223] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/2 to device 2 entity 2
[ 887.695233] uvcvideo: Adding mapping 'Brightness' to control
00000000-0000-0000-0000-000000000101/2.
[ 887.695246] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/3 to device 2 entity 2
[ 887.695256] uvcvideo: Adding mapping 'Contrast' to control
00000000-0000-0000-0000-000000000101/3.
[ 887.695269] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/7 to device 2 entity 2
[ 887.695279] uvcvideo: Adding mapping 'Saturation' to control
00000000-0000-0000-0000-000000000101/7.
[ 887.695293] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/8 to device 2 entity 2
[ 887.695303] uvcvideo: Adding mapping 'Sharpness' to control
00000000-0000-0000-0000-000000000101/8.
[ 887.695316] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/10 to device 2 entity 2
[ 887.695328] uvcvideo: Adding mapping 'White Balance Temperature' to
control 00000000-0000-0000-0000-000000000101/10.
[ 887.695341] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/1 to device 2 entity 2
[ 887.695352] uvcvideo: Adding mapping 'Backlight Compensation' to
control 00000000-0000-0000-0000-000000000101/1.
[ 887.695366] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/4 to device 2 entity 2
[ 887.695376] uvcvideo: Adding mapping 'Gain' to control
00000000-0000-0000-0000-000000000101/4.
[ 887.695389] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/5 to device 2 entity 2
[ 887.695401] uvcvideo: Adding mapping 'Power Line Frequency' to
control 00000000-0000-0000-0000-000000000101/5.
[ 887.695415] uvcvideo: Added control
00000000-0000-0000-0000-000000000101/11 to device 2 entity 2
[ 887.695426] uvcvideo: Adding mapping 'White Balance Temperature,
Auto' to control 00000000-0000-0000-0000-000000000101/11.
[ 887.695441] uvcvideo: Scanning UVC chain: OT 5 <- XU 4 (-> XU 6 XU
7) <- PU 2 (-> XU 3) <- IT 1
[ 887.695466] uvcvideo: Found a valid video chain (1 -> 5).
[ 887.792799] input: USBDevice as
/devices/pci0000:00/0000:00:00.0/usb3/3-2/3-2:1.0/input/input2
[ 887.801490] uvcvideo: UVC device initialized.



This is the lsusb output:

# lsusb
libudev: udev_has_devtmpfs: name_to_handle_at on /dev: Function not implemented
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 004: ID 046d:0825 Logitech, Inc. Webcam C270
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

However, I cannot access the camera:

# v4l2-ctl --all
Failed to open /dev/video0: No such device

in strace:

open("/dev/video0", O_RDWR) = -1 ENODEV (No such device)

I have tried different camera model, the C270 on another computer
(works fine), deleting /dev/video0 and re-creating it (mknod
/dev/video0 c 81 0), changing permissions, etc. but I get the same
error...

crw-rw-rw- 1 root video 81, 0 Jun 14 12:07 /dev/video0

lsmod shows that uvcvideo is not used for the camera:

# lsmod
Module Size Used by
uvcvideo 57657 0
videodev 72561 1 uvcvideo
usbcore 147080 7
ehci_hcd,etxhci_hcd,usb_storage,usblp,usbhid,uvcvideo
usb_common 592 1 usbcore

Any ideas?



Either I've been missing something or nothing has been going on. (K. E. Gordon)

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