HID: wacom: Support sequence numbers smaller than 16-bit

[ 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@wacom.com>
Tested-by: Joshua Dickens <joshua.dickens@wacom.com>
Fixes: 6d09085b38e5 ("HID: wacom: Adding Support for new usages")
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index d84740be96426ab308db03af551969c4abc4b785..8cf82a5f3a5bf7e893df0b13f769670c1429d5fb 100644 (file)
--- 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;
        }