On Tue, May 29, 2018 at 03:56:55PM -0700, Ben Chan wrote: > According to [1] and also seemingly agreed by [2], the Scan Time usage > (0x0D 0x56) is a report level usage, not a contact level usage. > > However, the hid-multitouch driver currently includes HID_DG_SCANTIME > when calculating `td->last_slot_field', which may lead to > mt_complete_slot() being prematurely called in certain cases (e.g. when > each touch input report includes more than one contact and the Scan Time > usage appears before any contact logical collection). > > This patch fixes the issue by skipping mt_store_field() on > HID_DG_SCANTIME, similar to how HID_DG_CONTACTCOUNT and > HID_DG_CONTACTMAX are handled. > > [1] https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/windows-precision-touchpad-required-hid-top-level-collections#windows-precision-touchpad-input-reports > [2] https://patchwork.kernel.org/patch/1742181/ > > Fixes: 29cc309d8bf19 ("HID: hid-multitouch: forward MSC_TIMESTAMP") > Signed-off-by: Ben Chan <benchan@xxxxxxxxxxxx> This looks reasonable to me. Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> > --- > drivers/hid/hid-multitouch.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c > index dad2fbb0e3f8..161551aab496 100644 > --- a/drivers/hid/hid-multitouch.c > +++ b/drivers/hid/hid-multitouch.c > @@ -620,13 +620,16 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi, > hid_map_usage(hi, usage, bit, max, > EV_MSC, MSC_TIMESTAMP); > input_set_capability(hi->input, EV_MSC, MSC_TIMESTAMP); > - mt_store_field(usage, td, hi); > /* Ignore if indexes are out of bounds. */ > if (field->index >= field->report->maxfield || > usage->usage_index >= field->report_count) > return 1; > td->scantime_index = field->index; > td->scantime_val_index = usage->usage_index; > + /* > + * We don't set td->last_slot_field as scan time is > + * global to the report. > + */ > return 1; > case HID_DG_CONTACTCOUNT: > /* Ignore if indexes are out of bounds. */ > -- > 2.17.0.921.gf22659ad46-goog > > -- > To unsubscribe from this list: send the line "unsubscribe linux-input" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
