[PATCH 20/20] HID: hid-multitouch: Add missing contact count detection

[Henrik Rydberg]

Some devices report the number of contacts via the CONTACTCOUNT usage,
rather than using the CONTACTMAX feature. Without this patch, such
devices will be capped to ten fingers, the default maximum. Fixes a
long-standing regression on 3M and similar panels.

Cc: Benjamin Tissoires <benjamin.tissoires@xxxxxxx>
Signed-off-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
---
Since this patch looks like it could be backported as-is: In 3.6,
maxcontacts may be modified after the slots have been initialized,
leaving the patch harmless but ineffective.

 drivers/hid/hid-multitouch.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index eee19c9..2fc5335 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -388,6 +388,8 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONTACTCOUNT:
+			if (td->maxcontacts < field->logical_maximum + 1)
+				td->maxcontacts = field->logical_maximum + 1;
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONTACTMAX:
-- 
1.7.12

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