Julian --

Julian Back wrote:
> I have been testing the g_serial serial gadget with my superh_udc driver
> on the 2.4.21 kernel.  It works when I send data from the host to the
> device but when I send from the device to the host I get extra characters.
> 
> Example:
> 
> device# echo 1234 >/dev/ttygs0
> 
> host# cat /dev/usb/tts/0
> 1234
> 1^^^^^
> 
> I don't think these extra characters are being introduced by the UDC
> driver, they seem to be being sent by the g_serial driver, possibly due
> to some problem with line discipline in the tty driver.  Here is some
> debug output, I can see the 1234 followed by CR/LF being sent but then
> gs_put_char gets called with the extra characters.  There also seems to
> be a timing issue as when I have really verbose debug the extra
> characters carry on forever.

Be sure echo is turned off, use "stty -echo < /dev/ttyUSB0"
on the host side and "stty -echo < /dev/ttygs0" on the device
side.  (The device names may not be quite right, I don't have
time right now to check.)

I have seen similar symptoms caused by each side echoing
characters bounce back and forth.

I will try to look into this more, but the echo problem is
my first guess.

-- Al


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