Hi Blaž, On Wed, Nov 6, 2019 at 12:03 PM Blaž Hrastnik <blaz@xxxxxxx> wrote: > > 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@xxxxxxx> > --- 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 > 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 >
