On Thu, 26 Jan 2012, Sebastian Andrzej Siewior wrote: > >>> You should not depend on this. However, the uas driver should not > >>> consider an unlinked data URB to indicate an error -- even if > >>> actual_length is 0. > >> > >> The UAS driver sets the scsi status to whatever the device set it in > >> its status/sense reply. So you might receive no error and no data > >> according to the race mentioned by Sarah. > > > > Why would you receive no data? All the data sent by the device should > > be received and stored in the host's buffers by the time the status is > > received, even if the status URB completes before the data URB. > > Because the XHCI core re-ordered the data and status URB and status > completed before data. So the data urb got canceled. That doesn't mean you received no data. No data means urb->actual_length == 0, whereas cancelled means urb->status == -ENOENT or -ECONNRESET. Those are two independent conditions; one can be true without the other. That's what would happen in this case. Since all the data was received by the host, urb->actual_length would be nonzero -- even if urb->status indicates an unlink. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
