[Ftdi-usb-sio-devel] Extending the ftdi_sio driver for RS-485 usage with the FT4232H

[Matt B. <mba...@gm...>]

Hello,

Looking for some help understanding the ftdi_sio driver.  I've used the
libftdi interface to this chip before and I'm not seeing many parallels in
the Kernel driver.

In the RS-485 configuration for the FT4232H, bit7 of the channel is used as
an output for TXD Enable.  In UART mode (the default used by ftdi_sio),
this is the input signal RI# (Ring Indicator).

Where does the ftdi_sio.c driver set the pin direction for the channel?  I
need to re-purpose this pin to be an input, and drive it high during TX
operations.

For reference, page 12 describes pin usage, page 19 describes RS-485
configuration:

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT4232H.pdf

Thanks,
Matt