linux-kernel - Half-duplex rs-485 on full-duplex UART.

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Message-ID: <48239d390806261356m57acbe4er4dd3d928c1493b88@mail.gmail.com>
Date:	Fri, 27 Jun 2008 00:56:26 +0400
From:	"Sergey Lapin" <slapinid@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Half-duplex rs-485 on full-duplex UART.

Hi, all!

I have a device with normal serial ports (at91sam9260-based) and
RS-485 half-duplex transceiver
installed for it and 1 GPIO for duplex control, 1=writing, 0=reading.
A problem is that I need to hack serial driver to support this GPIO
control, which I don't like.
I just need to set it to 1 before transmission and back to 0 when
transmission ends.

Most important thing is to set this bit to 1 before transfer starts,
so I can't just poll UART registers
from tasklet. So I had to hack into serial driver for that.

So questions are:

1. Is there some generic enough mechanism in kernel to handle such
tasks? so I mean external
serial transcievers support?

2. Is there any way to implement this task without touching, in my
case, drivers/serial/atmel_serial.c?

Thanks a lot,
S.
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