@@ -1047,7 +1047,13 @@ static psmouse_ret_t alps_process_byte(struct psmouse *psmouse)
{
struct alps_data *priv = psmouse->private;
- if ((psmouse->packet[0] & 0xc8) == 0x08) { /* PS/2 packet */
+ /*
+ * Check if we are dealing with a bare PS/2 packet, presumably from
+ * a device connected to the external PS/2 port. Because bare PS/2
+ * protocol does not have enough constant bits to self-synchronize
+ * properly we only do this if the device is fully synchronized.
+ */
+ if (!psmouse->out_of_sync_cnt && (psmouse->packet[0] & 0xc8) == 0x08) {
if (psmouse->pktcnt == 3) {
alps_report_bare_ps2_packet(psmouse, psmouse->packet,
true);
This is a note to let you know that I have just added a patch titled Input: alps - ignore potential bare packets when device is out of sync to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt2. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 2b2469f366858f4387a127d9bd4bf7a0b785bcd7 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Pali=20Roh=C3=A1r?= <pali.rohar@gmail.com> Date: Sat, 8 Nov 2014 12:45:23 -0800 Subject: Input: alps - ignore potential bare packets when device is out of sync MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 4ab8f7f320f91f279c3f06a9795cfea5c972888a upstream. 5th and 6th byte of ALPS trackstick V3 protocol match condition for first byte of PS/2 3 bytes packet. When driver enters out of sync state and ALPS trackstick is sending data then driver match 5th, 6th and next 1st bytes as PS/2. It basically means if user is using trackstick when driver is in out of sync state driver will never resync. Processing these bytes as 3 bytes PS/2 data cause total mess (random cursor movements, random clicks) and make trackstick unusable until psmouse driver decide to do full device reset. Lot of users reported problems with ALPS devices on Dell Latitude E6440, E6540 and E7440 laptops. ALPS device or Dell EC for unknown reason send some invalid ALPS PS/2 bytes which cause driver out of sync. It looks like that i8042 and psmouse/alps driver always receive group of 6 bytes packets so there are no missing bytes and no bytes were inserted between valid ones. This patch does not fix root of problem with ALPS devices found in Dell Latitude laptops but it does not allow to process some (invalid) subsequence of 6 bytes ALPS packets as 3 bytes PS/2 when driver is out of sync. So with this patch trackstick input device does not report bogus data when also driver is out of sync, so trackstick should be usable on those machines. Signed-off-by: Pali Rohár <pali.rohar@gmail.com> Tested-by: Pali Rohár <pali.rohar@gmail.com> Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/input/mouse/alps.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) -- 2.1.0