The patch titled
serial/8250: implement dtr/dsr handshaking
has been added to the -mm tree. Its filename is
serial-8250-implement-dtr-dsr-handshaking.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: serial/8250: implement dtr/dsr handshaking
From: Michael Westermann <michael@xxxxxxxxxx>
I make a driver for Point of Sale Printer, a wide range of Printers use
only a DTR/DSR hardware-handshaking. When I use a handshaking in
userspace, the printer has a overrun problem and our customer has a problem
with the tax office.
Add a simple DTR/DSR handhake with a small change of the code. Userspace
can select it with
cflags |= CDTRDSR;
The stty tool will need updating for this.
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/serial/8250.c | 11 +++++++----
drivers/serial/serial_core.c | 12 ++++++++++++
include/asm-i386/termbits.h | 1 +
include/linux/serial_core.h | 16 +++++++++-------
4 files changed, 29 insertions(+), 11 deletions(-)
diff -puN drivers/serial/8250.c~serial-8250-implement-dtr-dsr-handshaking drivers/serial/8250.c
--- a/drivers/serial/8250.c~serial-8250-implement-dtr-dsr-handshaking
+++ a/drivers/serial/8250.c
@@ -1400,12 +1400,15 @@ static unsigned int check_modem_status(s
up->port.info != NULL) {
if (status & UART_MSR_TERI)
up->port.icount.rng++;
- if (status & UART_MSR_DDSR)
- up->port.icount.dsr++;
if (status & UART_MSR_DDCD)
uart_handle_dcd_change(&up->port, status & UART_MSR_DCD);
- if (status & UART_MSR_DCTS)
- uart_handle_cts_change(&up->port, status & UART_MSR_CTS);
+ if (status & (UART_MSR_DCTS|UART_MSR_DDSR)) {
+ if (status & UART_MSR_DDSR)
+ up->port.icount.dsr++;
+ else
+ up->port.icount.cts++;
+ uart_handle_dsr_cts_change(&up->port, status & UART_MSR_CTS, status & UART_MSR_DSR);
+ }
wake_up_interruptible(&up->port.info->delta_msr_wait);
}
diff -puN drivers/serial/serial_core.c~serial-8250-implement-dtr-dsr-handshaking drivers/serial/serial_core.c
--- a/drivers/serial/serial_core.c~serial-8250-implement-dtr-dsr-handshaking
+++ a/drivers/serial/serial_core.c
@@ -192,6 +192,13 @@ static int uart_startup(struct uart_stat
spin_unlock_irq(&port->lock);
}
+ if (info->flags & UIF_DSR_FLOW) {
+ spin_lock_irq(&port->lock);
+ if (!(port->ops->get_mctrl(port) & TIOCM_DSR))
+ info->tty->hw_stopped = 1;
+ spin_unlock_irq(&port->lock);
+ }
+
info->flags |= UIF_INITIALIZED;
clear_bit(TTY_IO_ERROR, &info->tty->flags);
@@ -437,6 +444,11 @@ uart_change_speed(struct uart_state *sta
else
state->info->flags &= ~UIF_CTS_FLOW;
+ if (termios->c_cflag & CDTRDSR)
+ state->info->flags |= UIF_DSR_FLOW;
+ else
+ state->info->flags &= ~UIF_DSR_FLOW;
+
if (termios->c_cflag & CLOCAL)
state->info->flags &= ~UIF_CHECK_CD;
else
diff -puN include/asm-i386/termbits.h~serial-8250-implement-dtr-dsr-handshaking include/asm-i386/termbits.h
--- a/include/asm-i386/termbits.h~serial-8250-implement-dtr-dsr-handshaking
+++ a/include/asm-i386/termbits.h
@@ -157,6 +157,7 @@ struct ktermios {
#define B3500000 0010016
#define B4000000 0010017
#define CIBAUD 002003600000
+#define CDTRDSR 004000000000 /* dtrdsr flow control */
#define CMSPAR 010000000000 /* mark or space (stick) parity */
#define CRTSCTS 020000000000 /* flow control */
diff -puN include/linux/serial_core.h~serial-8250-implement-dtr-dsr-handshaking include/linux/serial_core.h
--- a/include/linux/serial_core.h~serial-8250-implement-dtr-dsr-handshaking
+++ a/include/linux/serial_core.h
@@ -335,6 +335,7 @@ struct uart_info {
* Definitions for info->flags. These are _private_ to serial_core, and
* are specific to this structure. They may be queried by low level drivers.
*/
+#define UIF_DSR_FLOW ((__force uif_t) (1 << 22))
#define UIF_CHECK_CD ((__force uif_t) (1 << 25))
#define UIF_CTS_FLOW ((__force uif_t) (1 << 26))
#define UIF_NORMAL_ACTIVE ((__force uif_t) (1 << 29))
@@ -494,26 +495,27 @@ uart_handle_dcd_change(struct uart_port
/**
* uart_handle_cts_change - handle a change of clear-to-send state
+ * when set DTR/DSR and RTS/CTS send only when both lines ok
* @port: uart_port structure for the open port
* @status: new clear to send status, nonzero if active
*/
static inline void
-uart_handle_cts_change(struct uart_port *port, unsigned int status)
+uart_handle_dsr_cts_change(struct uart_port *port, unsigned int status_cts, unsigned int status_dsr)
{
struct uart_info *info = port->info;
struct tty_struct *tty = info->tty;
+ int cts_stop = (info->flags & UIF_CTS_FLOW) && !status_cts;
+ int dsr_stop = (info->flags & UIF_DSR_FLOW) && !status_dsr;
- port->icount.cts++;
-
- if (info->flags & UIF_CTS_FLOW) {
+ if ((info->flags & UIF_CTS_FLOW) || (info->flags & UIF_DSR_FLOW)) {
if (tty->hw_stopped) {
- if (status) {
+ if (!(cts_stop||dsr_stop)) {
tty->hw_stopped = 0;
port->ops->start_tx(port);
uart_write_wakeup(port);
}
} else {
- if (!status) {
+ if (cts_stop||dsr_stop) {
tty->hw_stopped = 1;
port->ops->stop_tx(port);
}
@@ -544,7 +546,7 @@ uart_insert_char(struct uart_port *port,
* UART_ENABLE_MS - determine if port should enable modem status irqs
*/
#define UART_ENABLE_MS(port,cflag) ((port)->flags & UPF_HARDPPS_CD || \
- (cflag) & CRTSCTS || \
+ (cflag) & (CRTSCTS|CDTRDSR) || \
!((cflag) & CLOCAL))
#endif
_
Patches currently in -mm which might be from michael@xxxxxxxxxx are
serial-8250-implement-dtr-dsr-handshaking.patch
serial-8250-implement-dtr-dsr-handshaking-fix.patch
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