[PATCH 5/6] Input: ALPS - fix trackstick detection on some Dell Latitudes

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On some Dell Latitudes we fail to identify presence of trackstick unless we
reset the device. The issue is quite benign as we do perform reset in
alps_init(), so the trackstick ends up working, but mouse name reported to
userspace is not accurate.

In order to fix the issue while avoiding the additional lengthy reset we
move the resrt to alps_detect() and keep the discovered state to be used
later in alps_init().

Reported-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/input/mouse/alps.c | 74 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 55 insertions(+), 19 deletions(-)

diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index cabb267..fd3303d 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -2304,6 +2304,7 @@ static int alps_identify(struct psmouse *psmouse, struct alps_data *priv)
 {
 	const struct alps_protocol_info *protocol;
 	unsigned char e6[4], e7[4], ec[4];
+	int error;
 
 	/*
 	 * First try "E6 report".
@@ -2349,10 +2350,15 @@ static int alps_identify(struct psmouse *psmouse, struct alps_data *priv)
 		}
 	}
 
-	/* Save the Firmware version */
-	memcpy(priv->fw_ver, ec, 3);
+	if (priv) {
+		/* Save the Firmware version */
+		memcpy(priv->fw_ver, ec, 3);
+		error = alps_set_protocol(psmouse, priv, protocol);
+		if (error)
+			return error;
+	}
 
-	return alps_set_protocol(psmouse, priv, protocol);
+	return 0;
 }
 
 static int alps_reconnect(struct psmouse *psmouse)
@@ -2406,22 +2412,20 @@ static void alps_set_abs_params_mt(struct alps_data *priv,
 
 int alps_init(struct psmouse *psmouse)
 {
-	struct alps_data *priv;
+	struct alps_data *priv = psmouse->private;
 	struct input_dev *dev1 = psmouse->dev, *dev2;
+	int error;
 
-	priv = kzalloc(sizeof(struct alps_data), GFP_KERNEL);
 	dev2 = input_allocate_device();
-	if (!priv || !dev2)
+	if (!dev2) {
+		error = -ENOMEM;
 		goto init_fail;
+	}
 
 	priv->dev2 = dev2;
 
-	psmouse_reset(psmouse);
-
-	if (alps_identify(psmouse, priv) < 0)
-		goto init_fail;
-
-	if (priv->hw_init(psmouse))
+	error = priv->hw_init(psmouse);
+	if (error)
 		goto init_fail;
 
 	/*
@@ -2519,24 +2523,56 @@ int alps_init(struct psmouse *psmouse)
 init_fail:
 	psmouse_reset(psmouse);
 	input_free_device(dev2);
-	kfree(priv);
+	/*
+	 * Even though we did not allocate psmouse->private we do free
+	 * it here.
+	 */
+	kfree(psmouse->private);
 	psmouse->private = NULL;
-	return -1;
+	return error;
 }
 
 int alps_detect(struct psmouse *psmouse, bool set_properties)
 {
-	struct alps_data dummy;
+	struct alps_data *priv;
+	int error;
 
-	if (alps_identify(psmouse, &dummy) < 0)
-		return -1;
+	error = alps_identify(psmouse, NULL);
+	if (error)
+		return error;
+
+	/*
+	 * Reset the device to make sure it is fully operational:
+	 * on some laptops, like certain Dell Latitudes, we may
+	 * fail to properly detect presence of trackstick if device
+	 * has not been reset.
+	 */
+	psmouse_reset(psmouse);
+
+	priv = kzalloc(sizeof(struct alps_data), GFP_KERNEL);
+	if (priv)
+		return -ENOMEM;
+
+	error = alps_identify(psmouse, priv);
+	if (error)
+		return error;
 
 	if (set_properties) {
 		psmouse->vendor = "ALPS";
-		psmouse->name = dummy.flags & ALPS_DUALPOINT ?
+		psmouse->name = priv->flags & ALPS_DUALPOINT ?
 				"DualPoint TouchPad" : "GlidePoint";
-		psmouse->model = dummy.proto_version;
+		psmouse->model = priv->proto_version;
+	} else {
+		/*
+		 * Destroy alps_data structure we allocated earlier since
+		 * this was just a "trial run". Otherwise we'll keep it
+		 * to be used by alps_init() which has to be called if
+		 * we succeed and set_properties is true.
+		 */
+		kfree(priv);
+		psmouse->private = NULL;
 	}
+
 	return 0;
 }
 
-- 
2.2.0.rc0.207.ga3a616c

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