[PATCH 6.6 168/538] HID: wacom: Support sequence numbers smaller than 16-bit

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6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Gerecke <jason.gerecke@xxxxxxxxx>

[ Upstream commit 359673ea3a203611b4f6d0f28922a4b9d2cfbcc8 ]

The current dropped packet reporting assumes that all sequence numbers
are 16 bits in length. This results in misleading "Dropped" messages if
the hardware uses fewer bits. For example, if a tablet uses only 8 bits
to store its sequence number, once it rolls over from 255 -> 0, the
driver will still be expecting a packet "256". This patch adjusts the
logic to reset the next expected packet to logical_minimum whenever
it overflows beyond logical_maximum.

Signed-off-by: Jason Gerecke <jason.gerecke@xxxxxxxxx>
Tested-by: Joshua Dickens <joshua.dickens@xxxxxxxxx>
Fixes: 6d09085b38e5 ("HID: wacom: Adding Support for new usages")
Signed-off-by: Jiri Kosina <jkosina@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/hid/wacom_wac.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 5db26a8af7728..c3c576641a38e 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -2492,9 +2492,14 @@ static void wacom_wac_pen_event(struct hid_device *hdev, struct hid_field *field
 		wacom_wac->hid_data.barrelswitch3 = value;
 		return;
 	case WACOM_HID_WD_SEQUENCENUMBER:
-		if (wacom_wac->hid_data.sequence_number != value)
-			hid_warn(hdev, "Dropped %hu packets", (unsigned short)(value - wacom_wac->hid_data.sequence_number));
+		if (wacom_wac->hid_data.sequence_number != value) {
+			int sequence_size = field->logical_maximum - field->logical_minimum + 1;
+			int drop_count = (value - wacom_wac->hid_data.sequence_number) % sequence_size;
+			hid_warn(hdev, "Dropped %d packets", drop_count);
+		}
 		wacom_wac->hid_data.sequence_number = value + 1;
+		if (wacom_wac->hid_data.sequence_number > field->logical_maximum)
+			wacom_wac->hid_data.sequence_number = field->logical_minimum;
 		return;
 	}
 
-- 
2.43.0







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