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SERIAL: core: add hardware assisted s/w flow control support 

Ports which are capable of handling s/w flow control in hardware to
know when the s/w flow control termios settings are changed.  Add a
flag to allow the low level serial drivers to indicate that they
support this, and these changes should be propagated to them.

Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2012-04-17 16:34:13 +01:00
parent dec94e70e1
commit 2cbacafd7a
2 changed files with 16 additions and 2 deletions
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16
drivers/tty/serial/serial_core.c
View File

@ -1213,7 +1213,19 @@ static void uart_set_termios(struct tty_struct *tty,
struct uart_port *uport = state->uart_port;
unsigned long flags;
unsigned int cflag = tty->termios.c_cflag;
unsigned int iflag_mask = IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK;
bool sw_changed = false;
/*
* Drivers doing software flow control also need to know
* about changes to these input settings.
*/
if (uport->flags & UPF_SOFT_FLOW) {
iflag_mask |= IXANY|IXON|IXOFF;
sw_changed =
tty->termios.c_cc[VSTART] != old_termios->c_cc[VSTART] ||
tty->termios.c_cc[VSTOP] != old_termios->c_cc[VSTOP];
}
/*
* These are the bits that are used to setup various
@ -1221,11 +1233,11 @@ static void uart_set_termios(struct tty_struct *tty,
* bits in c_cflag; c_[io]speed will always be set
* appropriately by set_termios() in tty_ioctl.c
*/
#define RELEVANT_IFLAG(iflag) ((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))
if ((cflag ^ old_termios->c_cflag) == 0 &&
tty->termios.c_ospeed == old_termios->c_ospeed &&
tty->termios.c_ispeed == old_termios->c_ispeed &&
RELEVANT_IFLAG(tty->termios.c_iflag ^ old_termios->c_iflag) == 0) {
((tty->termios.c_iflag ^ old_termios->c_iflag) & iflag_mask) == 0 &&
!sw_changed) {
return;
}

2
include/linux/serial_core.h
View File

@ -163,6 +163,8 @@ struct uart_port {
#define UPF_BUGGY_UART ((__force upf_t) (1 << 14))
#define UPF_NO_TXEN_TEST ((__force upf_t) (1 << 15))
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))
/* Port has hardware-assisted s/w flow control */
#define UPF_SOFT_FLOW ((__force upf_t) (1 << 22))
#define UPF_CONS_FLOW ((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))
#define UPF_EXAR_EFR ((__force upf_t) (1 << 25))