[PATCH AUTOSEL 5.4 082/134] HID: Improve Windows Precision Touchpad detection.

Sasha Levin
2019-12-11T15:13:21Z

From: Blaž Hrastnik <blaz@mxxn.io>

[ Upstream commit 2dbc6f113acd74c66b04bf49fb027efd830b1c5a ]

Per Microsoft spec, usage 0xC5 (page 0xFF) returns a blob containing
data used to verify the touchpad as a Windows Precision Touchpad.

0x85, REPORTID_PTPHQA, // REPORT_ID (PTPHQA)
0x09, 0xC5, // USAGE (Vendor Usage 0xC5)
0x15, 0x00, // LOGICAL_MINIMUM (0)
0x26, 0xff, 0x00, // LOGICAL_MAXIMUM (0xff)
0x75, 0x08, // REPORT_SIZE (8)
0x96, 0x00, 0x01, // REPORT_COUNT (0x100 (256))
0xb1, 0x02, // FEATURE (Data,Var,Abs)

However, some devices, namely Microsoft's Surface line of products
instead implement a "segmented device certification report" (usage 0xC6)
which returns the same report, but in smaller chunks.

0x06, 0x00, 0xff, // USAGE_PAGE (Vendor Defined)
0x85, REPORTID_PTPHQA, // REPORT_ID (PTPHQA)
0x09, 0xC6, // USAGE (Vendor usage for segment #)
0x25, 0x08, // LOGICAL_MAXIMUM (8)
0x75, 0x08, // REPORT_SIZE (8)
0x95, 0x01, // REPORT_COUNT (1)
0xb1, 0x02, // FEATURE (Data,Var,Abs)
0x09, 0xC7, // USAGE (Vendor Usage)
0x26, 0xff, 0x00, // LOGICAL_MAXIMUM (0xff)
0x95, 0x20, // REPORT_COUNT (32)
0xb1, 0x02, // FEATURE (Data,Var,Abs)

By expanding Win8 touchpad detection to also look for the segmented
report, all Surface touchpads are now properly recognized by
hid-multitouch.

Signed-off-by: Blaž Hrastnik <blaz@mxxn.io>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/hid/hid-core.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 2fa3587d974f4..e0b241bd3070c 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -781,6 +781,10 @@ static void hid_scan_feature_usage(struct hid_parser *parser, u32 usage)
if (usage == 0xff0000c5 && parser->global.report_count == 256 &&
parser->global.report_size == 8)
parser->scan_flags |= HID_SCAN_FLAG_MT_WIN_8;
+
+ if (usage == 0xff0000c6 && parser->global.report_count == 1 &&
+ parser->global.report_size == 8)
+ parser->scan_flags |= HID_SCAN_FLAG_MT_WIN_8;
}

static void hid_scan_collection(struct hid_parser *parser, unsigned type)
--
2.20.1