On Thu, Nov 7, 2019 at 10:07 AM Blaž Hrastnik [off-list ref] wrote:

I've submitted a test containing the Surface Book 2 descriptor.

https://gitlab.freedesktop.org/libevdev/hid-tools/merge_requests/59

Thanks.

Patch is now queued in branch for-5.5/core.

Cheers,
Benjamin

Blaž

On Thu, 7 Nov 2019, at 17:48, Benjamin Tissoires wrote:

quoted

Hi Blaž,

On Wed, Nov 6, 2019 at 12:03 PM Blaž Hrastnik [off-list ref] wrote:

quoted

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 <redacted>
---

This looks good to me.
We *could* shorten the ifs and make only one conditional, but I find
it this way more readable and future proof.

There is just one last step required before we merge this: add a
regression test so we ensure we do not break it in the future.

It should be merely a matter of sending a MR to
https://gitlab.freedesktop.org/libevdev/hid-tools.
It should consist in adding the report descriptor in the same way we
have
https://gitlab.freedesktop.org/libevdev/hid-tools/blob/master/tests/test_multitouch.py#L1656-1658.
Then, make sure an unpatched kernel breaks the multitouch test (sudo
pytest-3 -k 'multitouch and TestPTP') and that a patched kernel is
fixed.

Cheers,
Benjamin

quoted

 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 63fdbf09b044..2af597cd5d65 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c

@@ -742,6 +742,10 @@ 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)
--

2.23.0