Hello,
I work with a logitech 4000 pro WebCam with the pwc driver; I run it on RH9 linux with 2.4.20-8 kernel.
The driver is part of the linux kernel 2.4.20-8. (and also above , of course).
Now , in pwc_isoc_init() method (in pwc-if.c) there is the following call: ret = usb_set_interface(pdev->udev, 0, pdev->valternate);
By debugging I saw that it uses alternate setting 2 (pdev->valternate=2).
Now , according to the next Linux Device Driver website , this is the descriptor for that webcam: (and I verified it by cat /proc/bus/usb/devices)
http://www.qbik.ch/usb/devices/showdescr.php?id=2515
Now , I had tried to use a different alternate setting,1, for which the Maximum Packet Size (MxPS) is 196.
So I set pdev->valternate to 1 in the beginning of the pwc_isoc_init().
the return value form usb_set_interface() is 0 ; this means success.
I also saw the the return value from usb_maxpacket is 196, which is indeed the
max packet size of alternate setting 1.
However, when I try to use a utility like ffmpeg to grab a video sequence it fails immeditately in the beginning : it simply hangs in the pwc_video_ioctl() method. (in the case VIDIOCSYNC: )
I don't understand why; though I added printk() calls almost everywhere in that case sentence of this pwc_video_ioctl() it does not reach them ; it simply hangs.
My question is :
Given that descriptor - is it possible and correct to change alternate setting like I do ?
Or should I do something else?
Is it OK that the number of endpoint remains 5 in both cases (when using altenate setting 2,which is the default,and when using alternate setting 1 ?)
Any help will be appreciated.
The kernel log I got when running the ffmpeg util is below: (I added some printing info where I thought it can give some hint):
[pwc-if.c] in pwc_isoc_init [pwc-if.c] in pdev->vendpoint = 5 [pwc-if.c] setting pdev->vmax_packet_size to 196 [pwc-if.c] usb_set_interface ret= 0 [pwc-if.c] pipe size is 164736 [pwc-if.c] epmaxpacketout= 0 epmaxpacketin 196 usb_pipeendpoint 5 [pwc-if.c] pipeout 0 [pwc-if.c] usb_maxpacket returns 196 [pwc-if.c] pipe size is 164736 [pwc-if.c] epmaxpacketout= 0 [pwc-if.c] epmaxpacketin 196 [pwc-if.c] usb_pipeendpoint 5 [pwc-if.c] pipeout 0 [pwc-if.c] usb_maxpacket returns 196 [pwc-if.c] finished pwc_isoc_init() [pwc-if.c] finished pwc_video_open [pwc-if.c] pwc_video_ioctl
[pwc-if.c] case VIDIOCMCAPTURE:
VIDIOCMCAPTURE: 352x288, frame 0, format 15
[pwc-if.c] before pwc_try_video_mode :
pwc Video mode [EMAIL PROTECTED] fps is only supported with the decompressor module (pwcx).
in pwc_isoc_init
in pdev->vendpoint = 5
[pwc-if.c] setting pdev->vmax_packet_size to 196
[pwc-if.c] usb_set_interface ret= 0
[pwc-if.c] pipe size is 164736
[pwc-if.c] epmaxpacketout= 0
[pwc-if.c] epmaxpacketin 196
[pwc-if.c] usb_pipeendpoint 5
[pwc-if.c] pipeout 0
[pwc-if.c] usb_maxpacket returns 196
[pwc-if.c] pipe size is 164736
[pwc-if.c] epmaxpacketout= 0
[pwc-if.c] epmaxpacketin 196
[pwc-if.c] usb_pipeendpoint 5
[pwc-if.c] pipeout 0
[pwc-if.c] usb_maxpacket returns 196
[pwc-if.c] finished pwc_isoc_init()
[pwc-if.c] after pwc_try_video_mode :
[pwc-if.c] VIDIOCMCAPTURE done :
[pwc-if.c] pwc_video_ioctl
[pwc-if.c] case VIDIOCMCAPTURE:
VIDIOCMCAPTURE: 352x288, frame 1, format 15
[pwc-if.c] VIDIOCMCAPTURE done :
[pwc-if.c] pwc_video_ioctl
[pwc-if.c] case VIDIOCSYNC:
regards, John
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