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> --- 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
