linux-kernel - [PATCH] Improve error recovery in serial mouse driver

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Message-ID: <m3k5xiqput.fsf@telia.com>
Date:	15 Mar 2007 20:16:42 +0100
From:	Peter Osterlund <petero2@...ia.com>
To:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] Improve error recovery in serial mouse driver

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@...ia.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@...ia.com
http://web.telia.com/~u89404340
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