Hi, I have noticed a problem using a usb device managed by the cdc_acm driver. The data received from the device and copied to userspace ends up being shifted by one byte again and again after some amount of calls to read() and most importantly with previously read data. usbmon shows the usb data payload is correct. A small shell script is enough to make it happen fastly: https://gist.github.com/Julio-Guerra/b6529994f814771c825649bdb8d927c2 It prints the buffer read with my device (a relay) and gives me things like: > 00 01 01 01 00 01 00 01 ... > 01 00 01 01 01 00 01 00 ... > 00 01 00 01 01 01 00 01 after a random number of times, while usbmon shows the usb payload "00 01 01 01 00 01 00 01" Another example: > 00 00 00 00 00 00 00 01 ... > 01 00 00 00 00 00 00 00 ... > 00 01 00 00 00 00 00 00 ... > 00 00 01 00 00 00 00 00 after a random number of times, while usbmon shows the usb payload "00 00 00 00 00 00 00 01". Any idea? I currently use versions 4.5.0 and 4.7.1 to execute this script. Thanks you -- Julio Guerra -- 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
