Hello all, We're seeing a strange problem when writing commands to a Sierra Wireless USB modem. It is a USB 1.1 device.
We're sending some commands over the control channel for the modem. Almost everything works fine. However, when sending commands larger than 64 bytes, the rest of the data (which was a part of that write) is corrupted, which we've seen using a USB sniffer. We have modified the userspace application so that it writes only up to 64 bytes at a time, sleeps a little, and then writes more. This works fine. The strange part is that we've seen no issues with using the PPPD application to connect to the Internet using the Sierra Wireless modem. And it has got to be writing more than 64 bytes at a time, though that is to a different device file (and therefore a different bulk endpoint). The even stranger part is that the sierra.c driver doesn't make any significant distinctions between the different USB bulk endpoints. They are mapped to their individual /dev/ttyUSBx device files, and that's it. They all have the same number of URBs, and the code paths for all the bulk endpoints are the same. So it isn't at all clear to me why everything would be fine with one endpoint, and not with another. Unless the system is negotiating different transfer parameters for the different endpoints (which aren't _exactly_ identical in hardware)... --------------------------------------------------------------- I'm in the process of adding some more debug to the Sierra Wireless driver to just dump the data going over that particular bulk endpoint. I'll also be trying to figure out what (if any) differences there are between the bulk endpoints from the kernel's point of view. However, if anyone has some suggestions on where else to look, I'd certainly appreciate it. Thanks, James Graves ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
