jazzman on 1 May 2007 17:21:18 -0000


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Re: [PLUG] V4L Maximum video devices?


Yep, and I even use that driver for another camera I occasionally pull 
out. The issue isn't how many cameras the drivers support, it's how many 
it supports at one time.

I actually found my answer. I usually start the programs from xwindows on 
the file server, but I tried doing it with VNC this time so I could still 
have access to the console on the physical machine (since the issue I'm 
seeing tends to hang the GUI). Once I did that I got a clear indicator on 
the console that something else was the problem.. I got a nice juicy 
kernel fault (included below if anyone is curious).

A quick lookup of the kernel message (Unable to handle kernel paging 
request...) returned the following page:

http://gentoo-wiki.com/HOWTO_logitech_quickcam_on_2.6.x_kernel

And about 3/4 down the page is the information I was looking for:

"If you only see a blackscreen using xawtv or gqcam and then the 
application crashes and the kernel log gives you something like this:

 
May 18 14:47:37 [kernel] ohci_hcd 0000:00:03.1: leak ed ef3340c0 (#81) 
state 2
May 18 14:48:00 [kernel] quickcam: Control URB error -2
May 18 14:48:00 [kernel] Unable to handle kernel paging request at virtual 
address 02000040
...
May 18 14:48:00 [kernel]  <1>Fixing recursive fault but reboot is needed!

you have to make sure the webcam is connected to a usb-hub (BUS) that does 
not have any other devices attached to it. "

So basically, the rule of thumb is webcams must be the only USB device on 
a given root hub or else things go south. Since I ended up with 2 cameras 
in one hub, the minute I opened the 2nd it caused some resource conflict 
and BOOM... So now I have to find either a USB bracket for my server or a 
USB expansion card. Are there any cards that DON'T work with linux that I 
should be aware of?

Oh well, thanks for the help.
Marc

Kernel Fault Message:
----------------------------------------
May  1 01:07:41 vault kernel: ohci_hcd 0000:00:03.0: leak ed dd0e60c0 
(#81) state 2
May  1 01:07:46 vault kernel: Unable to handle kernel paging request at 
virtual address 460977a2
May  1 01:07:46 vault kernel:  printing eip:
May  1 01:07:46 vault kernel: c025c2ef
May  1 01:07:46 vault kernel: *pde = 00000000
May  1 01:07:46 vault kernel: Oops: 0000 [#1]
May  1 01:07:46 vault kernel: last sysfs file: /block/hda/hda1/size
May  1 01:07:46 vault kernel: Modules linked in: appletalk ipv6 ppdev 
autofs4 hidp rfcomm l2cap bluetooth sunrpc ip_conntrack_netbios_ns 
ipt_REJECT xt_state ip_con$
May  1 01:07:46 vault kernel: CPU:    0
May  1 01:07:46 vault kernel: EIP:    0060:[<c025c2ef>]    Not tainted VLI
May  1 01:07:46 vault kernel: EFLAGS: 00210206   (2.6.15-1.2054_FC5 #1)
May  1 01:07:46 vault kernel: EIP is at usb_kill_urb+0x2f/0xf4
May  1 01:07:46 vault kernel: eax: 46097772   ebx: d18b8000   ecx: 
00000000   edx: d011c000
May  1 01:07:46 vault kernel: esi: dd0b82ac   edi: cf238480   ebp: 
dc814964   esp: d011cee0
May  1 01:07:46 vault kernel: ds: 007b   es: 007b   ss: 0068
May  1 01:07:46 vault kernel: Process esd (pid: 2270, threadinfo=d011c000 
task=cf57aaa0)
May  1 01:07:46 vault kernel: Stack: <0>00000024 00000001 dc4eb7a8 
c025f89d dc844000 dd3f3400 dc844000 00000000
May  1 01:07:46 vault kernel:        00000000 00200286 ced23e00 c025c5ab 
cf238480 00000002 dd0b82ac cf238480
May  1 01:07:46 vault kernel:        dea37cb9 dd0b8000 00000000 dea3991d 
00000008 c01533d9 dd21f8bc ddfe3d20
May  1 01:07:46 vault kernel: Call Trace:
May  1 01:07:46 vault kernel:  [<c025f89d>] 
usb_create_sysfs_intf_files+0x68/0x7a     [<c025c5ab>] urb_destroy+0x0/0x5
May  1 01:07:46 vault kernel:  [<dea37cb9>] qc_isoc_stop+0xaf/0xcb 
[quickcam]     [<dea3991d>] qc_v4l_close+0x59/0xa5 [quickcam]
May  1 01:07:46 vault kernel:  [<c01533d9>] __fput+0xae/0x151     
[<c0150efb>] filp_close+0x4e/0x54
May  1 01:07:46 vault kernel:  [<c011bd5f>] put_files_struct+0x63/0xa5     
[<c011d048>] do_exit+0x1db/0x6c8
May  1 01:07:46 vault kernel:  [<c011d5b9>] sys_exit_group+0x0/0xd     
[<c0102bc1>] syscall_call+0x7/0xb

 On Tue, 1 May 2007, Greg Helledy wrote:

>  >I don't have any other cameras that really work with
>  >Linux (I don't think... this brings up some interesting questions 
>  >actually about which cameras I have work... but that's tinkering for 
>  >another day).
> 
> Have you seen the Slashdot article about the guy who's recently written 
> linux drivers for 352 webcams?
> http://linux.slashdot.org/linux/07/04/30/209201.shtml
> Here is the guy's website:
> http://mxhaard.free.fr/spca5xx.html
> 
> You might have more linux-compatible cameras than you thought.
> 
> Greg Helledy
> 
> 


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