[PATCH] Improve error recovery in serial mouse driver

[PATCH] Improve error recovery in serial mouse driver

[Peter Osterlund]

If bytes get lost in the communication with a serial mouse using the
MS protocol, the kernel driver could do a better job getting back in
sync. The first byte in a packet has bit 6 set, and no other bytes
have that bit set. Therefore, if a byte is received with bit 6 cleared
when the driver thinks it is at byte 0 in the packet, the driver thinks
wrong and the byte should just be ignored.

This fix prevents spurious left/right button events when the serial
communication is disturbed by a CPU-hungry real-time process.

Signed-off-by: Peter Osterlund <petero2@telia.com>
---

 drivers/input/mouse/sermouse.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/input/mouse/sermouse.c b/drivers/input/mouse/sermouse.c
index a85d747..24bed4b 100644
--- a/drivers/input/mouse/sermouse.c
+++ b/drivers/input/mouse/sermouse.c
@@ -108,6 +108,7 @@ static void sermouse_process_ms(struct sermouse *sermouse, signed char data)
 	signed char *buf = sermouse->buf;
 
 	if (data & 0x40) sermouse->count = 0;
+	else if (sermouse->count == 0) return;
 
 	switch (sermouse->count) {
 

-- 
Peter Osterlund - petero2@telia.com
http://web.telia.com/~u89404340

Re: [PATCH] Improve error recovery in serial mouse driver

[Dmitry Torokhov]

On Thursday 15 March 2007 15:16, Peter Osterlund wrote:
> If bytes get lost in the communication with a serial mouse using the
> MS protocol, the kernel driver could do a better job getting back in
> sync. The first byte in a packet has bit 6 set, and no other bytes
> have that bit set. Therefore, if a byte is received with bit 6 cleared
> when the driver thinks it is at byte 0 in the packet, the driver thinks
> wrong and the byte should just be ignored.
> 
> This fix prevents spurious left/right button events when the serial
> communication is disturbed by a CPU-hungry real-time process.
> 
> Signed-off-by: Peter Osterlund <petero2@telia.com>

Applied, thank you Peter.

-- 
Dmitry

Re: [PATCH] Improve error recovery in serial mouse driver

[Chuck Ebbert]

Peter Osterlund wrote:
>  	if (data & 0x40) sermouse->count = 0;
> +	else if (sermouse->count == 0) return;

	if (data & 0x40)
		sermouse->count = 0;
	else
		if (sermouse->count == 0)
			return;


?

Would have been a good time to clean that one up...