USB synchronous control transfers (for usb-to-serial)

[Hans Petter Selasky]

> 
> Hi,
> 
> Attached is the patch adding a 250ms polling control transfer to
> update the port status flags. I've also added CRTSCTS hardware flow
> control. I did some tests with minicom and with gtkterm. Minicom works
> perfectly, but gtkterm has problems at baud 115200 and also with
> hardware flow control. I also testes the Prolific driver (uplcom) with
> minicom and gtkterm, and gtkterm has the same problems at 115200 baud,
> so I'm assuming it's  a gtkterm bug (not maintained anymore).
> 
> BTW, do the usb-to-serial drivers need the force_short_xfer usb
> transfer flag? gtkterm seems to work slightly better without the
> flag...
> 
> Anyway, thanks for the help so far

You can remove the force_short_xfer usb transfer flag, if you can verify that 
the chip receive data if you send a USB packet of exactly 64 or 512 bytes, 
depending on USB full or high-speed.

--HPS