Input: elantech - relax signature checks

Apparently there are Elantech touchpads that report non-zero in the 2nd byte
of their signature. Adjust the detection routine so that if 2nd byte is
zero and 3rd byte contains value that is not a valid report rate, we still
assume that signature is valid.

Tested-by: Eric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 19 insertions, 1 deletions

diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
index 232556a89c4a..b18862b2a70e 100644
--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -575,6 +575,24 @@ static struct attribute_group elantech_attr_group = {
         .attrs = elantech_attrs,
 };
 
+static bool elantech_is_signature_valid(const unsigned char *param)
+{
+        static const unsigned char rates[] = { 200, 100, 80, 60, 40, 20, 10 };
+        int i;
+
+        if (param[0] == 0)
+                return false;
+
+        if (param[1] == 0)
+                return true;
+
+        for (i = 0; i < ARRAY_SIZE(rates); i++)
+                if (param[2] == rates[i])
+                        return false;
+
+        return true;
+}
+
 /*
  * Use magic knock to detect Elantech touchpad
  */
@@ -617,7 +635,7 @@ int elantech_detect(struct psmouse *psmouse, bool set_properties)
         pr_debug("Elantech version query result 0x%02x, 0x%02x, 0x%02x.\n",
                  param[0], param[1], param[2]);
 
-        if (param[0] == 0 || param[1] != 0) {
+        if (!elantech_is_signature_valid(param)) {
                 if (!force_elantech) {
                         pr_debug("Probably not a real Elantech touchpad. Aborting.\n");
                         return -1;