On Thu, May 15, 2014 at 6:53 PM, Miner, Blake <bminer@xxxxxxxxxxxxxxxx> wrote: > After debugging further, I figured out what was causing the problem. > > In the driver for the cp210x, there is a line of code in the `.attach` > function that calls `usb_reset_device(serial->dev);`. See the source > code here: https://github.com/torvalds/linux/blob/master/drivers/usb/serial/cp210x.c#L859 > > This call to `usb_reset_device` causes the device to be reset just > before the second interface is detected. For whatever reason, the > reset prevents the second interface from being created in `/dev/`. > > By simply removing this line, both interfaces are properly detected > the first time. Unfortunately, there is a comment above this line > that reads "/* cp210x buffers behave strangely unless device is reset > */" Therefore, this reset might actually be necessary in order to > clear the buffers of the CP210x. In this case, when is the > appropriate time to perform a device reset so that both interfaces are > properly detected? > > Thanks, I am not sure about this, but I wonder can we do the reset in cp210x_open() instead of in cp210x_startup()? -Jidong -- 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
