Patch "HID: wacom: Fix poor prox handling in 'wacom_pl_irq'" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

HID: wacom: Fix poor prox handling in 'wacom_pl_irq'

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
hid-wacom-fix-poor-prox-handling-in-wacom_pl_irq.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jason Gerecke <[email protected]>
Date: Thu, 26 Jan 2017 09:06:22 -0800
Subject: HID: wacom: Fix poor prox handling in 'wacom_pl_irq'

From: Jason Gerecke <[email protected]>

commit 282e4637bc1c0b338708bcebd09d31c69abec070 upstream.

Commit 025bcc1 performed cleanup work on the 'wacom_pl_irq' function, making it follow the standards used in the rest of the codebase. The change unintiontionally allowed the function to send input events from reports that are not marked as being in prox. This can cause problems as the report values for X, Y, etc. are not guaranteed to be correct. In particular, occasionally the tablet will send a report with these values set to zero. If such a report is received it can caus an unexpected jump in the XY position.

This patch surrounds more of the processing code with a proximity check, preventing these zeroed reports from overwriting the current state. To be safe, only the tool type and ABS_MISC events should be reported when the pen is marked as being out of prox.

---
 drivers/hid/wacom_wac.c |   24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

@@ -164,19 +164,21 @@ static int wacom_pl_irq(struct wacom_wac
 		wacom->id[0] = STYLUS_DEVICE_ID;
 	}
 
-	pressure = (signed char)((data[7] << 1) | ((data[4] >> 2) & 1));
-	if (features->pressure_max > 255)
-		pressure = (pressure << 1) | ((data[4] >> 6) & 1);
-	pressure += (features->pressure_max + 1) / 2;
+	if (prox) {
+		pressure = (signed char)((data[7] << 1) | ((data[4] >> 2) & 1));
+		if (features->pressure_max > 255)
+			pressure = (pressure << 1) | ((data[4] >> 6) & 1);
+		pressure += (features->pressure_max + 1) / 2;
 
-	input_report_abs(input, ABS_X, data[3] | (data[2] << 7) | ((data[1] & 0x03) << 14));
-	input_report_abs(input, ABS_Y, data[6] | (data[5] << 7) | ((data[4] & 0x03) << 14));
-	input_report_abs(input, ABS_PRESSURE, pressure);
+		input_report_abs(input, ABS_X, data[3] | (data[2] << 7) | ((data[1] & 0x03) << 14));
+		input_report_abs(input, ABS_Y, data[6] | (data[5] << 7) | ((data[4] & 0x03) << 14));
+		input_report_abs(input, ABS_PRESSURE, pressure);
 
-	input_report_key(input, BTN_TOUCH, data[4] & 0x08);
-	input_report_key(input, BTN_STYLUS, data[4] & 0x10);
-	/* Only allow the stylus2 button to be reported for the pen tool. */
-	input_report_key(input, BTN_STYLUS2, (wacom->tool[0] == BTN_TOOL_PEN) && (data[4] & 0x20));
+		input_report_key(input, BTN_TOUCH, data[4] & 0x08);
+		input_report_key(input, BTN_STYLUS, data[4] & 0x10);
+		/* Only allow the stylus2 button to be reported for the pen tool. */
+		input_report_key(input, BTN_STYLUS2, (wacom->tool[0] == BTN_TOOL_PEN) && (data[4] & 0x20));
+	}
 
 	if (!prox)
 		wacom->id[0] = 0;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/hid-wacom-fix-poor-prox-handling-in-wacom_pl_irq.patch