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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: 6d09085b38 ("HID: wacom: Adding Support for new usages")
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jason Gerecke 2024-09-09 13:32:07 -07:00 committed by Greg Kroah-Hartman
parent cafeba3c2a
commit 85572bf646
1 changed files with 7 additions and 2 deletions
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9
drivers/hid/wacom_wac.c
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@ -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;
}