On Tue, Nov 28, 2006 at 12:31:58PM +0800, xiaoxin liu wrote: > Alan Stern ??????: > > On Tue, 28 Nov 2006, xiaoxin liu wrote: > > > > > >> Hi, Currently I got a philips webcam (type 740), which can be driven by > >> pwc in Linux. > >> > >> Now I want to write my own program to test the isochronus transfer > >> function of the device, not using the pwc driver. > >> > >> So I found out the device node in /proc/bus/usb/* and open it, then use > >> such an ioctl(fd, USBDEVFS_SUBMITURB, struct userspace_urb...) call to > >> send a isoc urb to the device. > >> > >> My urb includes fields like below: > >> > >> type = 0 (ISOC transfer) > >> endpoint = 0x85 (ISOC IN endpoint) > >> status = 0; > >> flags = 2 (USBDEVFS_URB_ISO_ASAP) > >> buffer = isoc_buf (isoc_buf was defined as char isoc_buf[9600]) > >> buffer_length = sizeof (isoc_buf) > >> actual_length = 0; > >> start_frame = 0; > >> number_of_packets = 10 > >> error_count = 0; > >> signr = 0 > >> usercontext = the address of urb structure > >> > >> The wMaxPacketSize of the isoc endpoint is 960. > >> > >> while I send out this urb, I hope to receive some data from the webcam > >> device. but I receive nothing, the actual_length = 0. > >> > >> Could anybody tell me why? > >> > > > > Did you fill in the contents of urb->iso_frame_desc[]? > > > yes, I did fill in the urb->iso_frame_desc[], and from 0 to 9 (because > number of packets = 10), I set the length member of iso_frame_desc[] as > 960, which is the maxPacketSize. > > > > What was the return code from the USBDEVFS_SUBMITURB ioctl call? > > > > > the return code for the ioctl call is 0, It seems that it has > successfully returned. but I can't see any new data in my receive buffer. > > Did you remember to make a USBDEVFS_REAPURB ioctl call? > > > > > I did't make a USBDEVFS_REAPURB ioctl call. Must I make this call?? > > Are you certain the camera was trying to send ISO data? > > > > > Currently, I only know the camera is powered on. So I created a ISO > transfer URB to the webcam, I think it should reply some data to me. > What I want to do is to let the webcam reply to me.
But that's probably not how this webcam works. You might try reading the specs for the device to figure out how to properly talk to the device (most need some setup before they start streaming data). good luck, greg k-h ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
