Input: psmouse - add support for Cortron PS/2 Trackballs

Cortron PS/2 Trackballs (700-0001A) report the 4th button using the 4th
bit of the first packet (yes, it breaks the standard PS/2 protocol).
This patch adds an extra protocol to generate BTN_SIDE based on the 4th
bit. There's no way to detect those trackballs using any kind of special
sequence, thus the protocol must be activated explicitely by writing
into 'protocol' sysfs attribute:

	echo -n "cortps" > /sys/devices/platform/i8042/serio1/protocol

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/mouse/psmouse-base.c b/drivers/input/mouse/psmouse-base.c
index f15f695..b9f0fb2 100644
--- a/drivers/input/mouse/psmouse-base.c
+++ b/drivers/input/mouse/psmouse-base.c
@@ -178,6 +178,15 @@
 	}
 
 /*
+ * Cortron PS2 Trackball reports SIDE button on the 4th bit of the first
+ * byte.
+ */
+	if (psmouse->type == PSMOUSE_CORTRON) {
+		input_report_key(dev, BTN_SIDE, (packet[0] >> 3) & 1);
+		packet[0] |= 0x08;
+	}
+
+/*
  * Generic PS/2 Mouse
  */
 
@@ -539,6 +548,20 @@
 	return 0;
 }
 
+/*
+ * Cortron PS/2 protocol detection. There's no special way to detect it, so it
+ * must be forced by sysfs protocol writing.
+ */
+static int cortron_detect(struct psmouse *psmouse, int set_properties)
+{
+	if (set_properties) {
+		psmouse->vendor = "Cortron";
+		psmouse->name = "PS/2 Trackball";
+		set_bit(BTN_SIDE, psmouse->dev->keybit);
+	}
+
+	return 0;
+}
 
 /*
  * psmouse_extensions() probes for any extensions to the basic PS/2 protocol
@@ -740,6 +763,12 @@
 	},
 #endif
 	{
+		.type		= PSMOUSE_CORTRON,
+		.name		= "CortronPS/2",
+		.alias		= "cortps",
+		.detect		= cortron_detect,
+	},
+	{
 		.type		= PSMOUSE_AUTO,
 		.name		= "auto",
 		.alias		= "any",
diff --git a/drivers/input/mouse/psmouse.h b/drivers/input/mouse/psmouse.h
index 3964e8a..27a6883 100644
--- a/drivers/input/mouse/psmouse.h
+++ b/drivers/input/mouse/psmouse.h
@@ -88,6 +88,7 @@
 	PSMOUSE_LIFEBOOK,
 	PSMOUSE_TRACKPOINT,
 	PSMOUSE_TOUCHKIT_PS2,
+	PSMOUSE_CORTRON,
 	PSMOUSE_AUTO		/* This one should always be last */
 };