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

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>

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 36010c515f39c01bd1c432b6bb7af5a40b06cede..22b0d281ff5ca813a37d212415472b3ef6110965 100644 (file)
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -2510,9 +2510,14 @@ 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;
        }