Greg KH wrote: > On Tue, Jun 05, 2007 at 03:26:07PM -0500, James Graves wrote: >> 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. > > How are you sending these commands? The current in-kernel driver > doesn't support this from what I can see, right?
This is from a user-space application. There's no special support in the in-kernel driver, nor does there need to be. >> 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. > > Corrupted where, coming from the host to the device? This is coming from the host, going to the modem. > Are you sure you aren't just forgetting to "encode" your data properly > as the device specs show that you need to do so? I can dig up the > relevant reference if you need it. Yeah, pretty sure. In the application, we're dumping out the data right before the glib call to write the data to the modem, and it is in the proper format with the correct escape sequences as needed. >> 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. > > This sounds odd, what endpoint pair are you sending to? This is endpoint 4 (bulk), which is using Sierra Wireless's control protocol. >> 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). > > Which device is this? Sorry, should have mentioned this to begin with. It is the MC8775. We've been doing some further testing, and there are some cases where everything seems to work fine. So we haven't yet completely isolated the conditions where things break or work correctly. It may well not be a USB transport issue at all. As suggested, we've also been looking at the output of usbmon. However, there are some things happening there that I don't quite understand, which I can post about separately. 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
