Add a notion about 16C950 UART, that is using DTR signal for RS485 mode.
Signed-off-by: Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx>
Index: b/Documentation/serial/serial-rs485.txt
===================================================================
--- a/Documentation/serial/serial-rs485.txt 2010-11-19 03:48:08.000000000 +0100
+++ b/Documentation/serial/serial-rs485.txt 2010-11-19 10:42:22.000000000 +0100
@@ -11,10 +11,11 @@
2. HARDWARE-RELATED CONSIDERATIONS
- Some CPUs (e.g., Atmel AT91) contain a built-in half-duplex mode capable of
- automatically controlling line direction by toggling RTS. That can used to
- control external half-duplex hardware like an RS485 transceiver or any
- RS232-connected half-duplex device like some modems.
+ Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in
+ half-duplex mode capable of automatically controlling line direction by
+ toggling RTS or DTR signals. That can be used to control external
+ half-duplex hardware like an RS485 transceiver or any RS232-connected
+ half-duplex devices like some modems.
For these microcontrollers, the Linux driver should be made capable of
working in both modes, and proper ioctls (see later) should be made
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