serial: Fix send_xchar() handlers

START_CHAR() & STOP_CHAR() can be disabled if set to '\0' (__DISABLED_CHAR). UART drivers which define a send_xchar() handler must not transmit __DISABLED_CHAR. Document requirement. Affected drivers: sunsab sunhv cc: David S. Miller <[email protected]> cc: <[email protected]> Signed-off-by: Peter Hurley <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
ambv · Sep 8, 2014 · db106df · db106df
1 parent fba594a
commit db106df
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diff --git a/Documentation/serial/driver b/Documentation/serial/driver
@@ -140,6 +140,8 @@ hardware.
 	will append the character to the circular buffer and then call
 	start_tx() / stop_tx() to flush the data out.
 
+	Do not transmit if ch == '\0' (__DISABLED_CHAR).
+
 	Locking: none.
 	Interrupts: caller dependent.
 

diff --git a/drivers/tty/serial/sunhv.c b/drivers/tty/serial/sunhv.c
@@ -268,6 +268,9 @@ static void sunhv_send_xchar(struct uart_port *port, char ch)
 	unsigned long flags;
 	int limit = 10000;
 
+	if (ch == __DISABLED_CHAR)
+		return;
+
 	spin_lock_irqsave(&port->lock, flags);
 
 	while (limit-- > 0) {

diff --git a/drivers/tty/serial/sunsab.c b/drivers/tty/serial/sunsab.c
@@ -468,6 +468,9 @@ static void sunsab_send_xchar(struct uart_port *port, char ch)
 	struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;
 	unsigned long flags;
 
+	if (ch == __DISABLED_CHAR)
+		return;
+
 	spin_lock_irqsave(&up->port.lock, flags);
 
 	sunsab_tec_wait(up);