[PATCH] HID: multitouch: Fetch feature reports on demand for Win8 devices

[Mika Westerberg]

Some newer Intel Skylake based Dell laptops with Win8 precision touchpad
fail when initial feature reports are fetched from it. Below is an example
output with some additional debug included:

 i2c_hid i2c-DLL0704:01: Fetching the HID descriptor
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=20 00
 i2c_hid i2c-DLL0704:01: HID Descriptor: 1e 00 00 01 99 02 21 00 24 ...
 ...
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 38 02 23 00
 i2c_hid i2c-DLL0704:01: report (len=4): 04 00 08 05
 i2c_hid i2c-DLL0704:01: report id 13
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 3d 02 23 00
 i2c_hid i2c-DLL0704:01: failed to retrieve report from device.
 i2c_hid i2c-DLL0704:01: report id 7
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 37 02 23 00
 i2c_hid i2c-DLL0704:01: report (len=259): 03 01 07 fc 28 fe 84 40 ...
 i2c_hid i2c-DLL0704:01: report id 4
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 34 02 23 00

We manage to fetch few reports but then the touchpad dies:

 i2c_designware i2c_designware.1: i2c_dw_handle_tx_abort: lost arbitration
 i2c_hid i2c-DLL0704:01: failed to retrieve report from device.

it eventually pulls the whole I2C bus low:

 i2c_designware i2c_designware.1: controller timed out
 i2c_hid i2c-DLL0704:01: failed to set a report to device.

Fix this by preventing initial feature report retrieval for Win8 devices.
Instead we fetch reports as needed in mt_feature_mapping(). This prevents
fetching reports which might cause problems with the device in question.

Suggested-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
---
This is a second version. The first one which just prevented initial report
reading can be found here:

  https://lkml.org/lkml/2015/9/24/191

This version tries to do what Benjamin suggested by reading feature values
as needed in mt_feature_mapping(). This fixes the issue in the Dell laptop
I have here.

 drivers/hid/hid-multitouch.c | 42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 661b4fce1a5d..d9ca2b96ab68 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -309,6 +309,38 @@ static struct attribute_group mt_attribute_group = {
 	.attrs = sysfs_attrs
 };
 
+static void mt_get_feature(struct hid_device *hdev, struct hid_report *report)
+{
+	int ret, size = hid_report_len(report);
+	u8 *buf;
+
+	/*
+	 * Only fetch the feature report if initial reports are not already
+	 * been retrieved. Currently this is only done for Windows 8 touch
+	 * devices.
+	 */
+	if (!(hdev->quirks & HID_QUIRK_NO_INIT_REPORTS))
+		return;
+
+	buf = hid_alloc_report_buf(report, GFP_KERNEL);
+	if (!buf)
+		return;
+
+	ret = hid_hw_raw_request(hdev, report->id, buf, size,
+				 HID_FEATURE_REPORT, HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		dev_warn(&hdev->dev, "failed to fetch feature %d\n",
+			 report->id);
+	} else {
+		ret = hid_report_raw_event(hdev, HID_FEATURE_REPORT, buf,
+					   size, 0);
+		if (ret)
+			dev_warn(&hdev->dev, "failed to report feature\n");
+	}
+
+	kfree(buf);
+}
+
 static void mt_feature_mapping(struct hid_device *hdev,
 		struct hid_field *field, struct hid_usage *usage)
 {
@@ -327,6 +359,8 @@ static void mt_feature_mapping(struct hid_device *hdev,
 
 		break;
 	case HID_DG_CONTACTMAX:
+		mt_get_feature(hdev, field->report);
+
 		td->maxcontact_report_id = field->report->id;
 		td->maxcontacts = field->value[0];
 		if (!td->maxcontacts &&
@@ -343,6 +377,7 @@ static void mt_feature_mapping(struct hid_device *hdev,
 			break;
 		}
 
+		mt_get_feature(hdev, field->report);
 		if (field->value[usage->usage_index] == MT_BUTTONTYPE_CLICKPAD)
 			td->is_buttonpad = true;
 
@@ -1029,8 +1064,13 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 		 * reports. Fortunately, the Win8 spec says that all touches
 		 * should be sent during each report, making the initialization
 		 * of input reports unnecessary.
+		 *
+		 * In addition some touchpads do not behave well if we read
+		 * all feature reports from them. Instead we prevent
+		 * initial report fetching and then selectively fetch each
+		 * report we are interested in.
 		 */
-		hdev->quirks |= HID_QUIRK_NO_INIT_INPUT_REPORTS;
+		hdev->quirks |= HID_QUIRK_NO_INIT_REPORTS;
 
 	td = devm_kzalloc(&hdev->dev, sizeof(struct mt_device), GFP_KERNEL);
 	if (!td) {
-- 
2.5.1

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