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tty: Add software emulated RS485 support for 8250

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Implementation of software emulation of RS485 direction handling is based
on omap_serial driver.
Before and after transmission RTS is set to the appropriate value.

Note that before calling serial8250_em485_init() the caller has to
ensure that UART will interrupt when shift register empty. Otherwise,
emultaion cannot be used.

Both serial8250_em485_init() and serial8250_em485_destroy() are
idempotent functions.

Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Matwey V. Kornilov 2016-02-01 21:09:21 +03:00 • committed by Greg Kroah-Hartman
parent a07a70bcb7
commit e490c9144c
3 changed files with 229 additions and 4 deletions
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8
include/linux/serial_8250.h
View file

@ -76,6 +76,12 @@ struct uart_8250_ops {
void (*release_irq)(struct uart_8250_port *);
};
struct uart_8250_em485 {
struct timer_list start_tx_timer; /* "rs485 start tx" timer */
struct timer_list stop_tx_timer; /* "rs485 stop tx" timer */
struct timer_list *active_timer; /* pointer to active timer */
};
/*
* This should be used by drivers which want to register
* their own 8250 ports without registering their own
@ -122,6 +128,8 @@ struct uart_8250_port {
/* 8250 specific callbacks */
int (*dl_read)(struct uart_8250_port *);
void (*dl_write)(struct uart_8250_port *, int);
struct uart_8250_em485 *em485;
};
static inline struct uart_8250_port *up_to_u8250p(struct uart_port *up)