95 lines
4.5 KiB
Diff
95 lines
4.5 KiB
Diff
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From cd1e1e286bb3c4fa8714c1e571ae082e510efd5d Mon Sep 17 00:00:00 2001
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From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
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Date: Tue, 1 Dec 2015 12:41:38 +0100
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Subject: [PATCH] HID: multitouch: fix input mode switching on some Elan panels
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as reported by https://bugzilla.kernel.org/show_bug.cgi?id=108481
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This bug reports mentions 6d4f5440 ("HID: multitouch: Fetch feature
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reports on demand for Win8 devices") as the origin of the problem but this
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commit actually masked 2 firmware bugs that are annihilating each other:
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The report descriptor declares two features in reports 3 and 5:
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0x05, 0x0d, // Usage Page (Digitizers) 318
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0x09, 0x0e, // Usage (Device Configuration) 320
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0xa1, 0x01, // Collection (Application) 322
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0x85, 0x03, // Report ID (3) 324
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0x09, 0x22, // Usage (Finger) 326
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0xa1, 0x00, // Collection (Physical) 328
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0x09, 0x52, // Usage (Inputmode) 330
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0x15, 0x00, // Logical Minimum (0) 332
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0x25, 0x0a, // Logical Maximum (10) 334
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0x75, 0x08, // Report Size (8) 336
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0x95, 0x02, // Report Count (2) 338
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0xb1, 0x02, // Feature (Data,Var,Abs) 340
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0xc0, // End Collection 342
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0x09, 0x22, // Usage (Finger) 343
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0xa1, 0x00, // Collection (Physical) 345
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0x85, 0x05, // Report ID (5) 347
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0x09, 0x57, // Usage (Surface Switch) 349
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0x09, 0x58, // Usage (Button Switch) 351
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0x15, 0x00, // Logical Minimum (0) 353
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0x75, 0x01, // Report Size (1) 355
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0x95, 0x02, // Report Count (2) 357
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0x25, 0x03, // Logical Maximum (3) 359
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0xb1, 0x02, // Feature (Data,Var,Abs) 361
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0x95, 0x0e, // Report Count (14) 363
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0xb1, 0x03, // Feature (Cnst,Var,Abs) 365
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0xc0, // End Collection 367
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The report ID 3 presents 2 input mode features, while only the first one
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is handled by the device. Given that we did not checked if one was
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previously assigned, we were dealing with the ignored featured and we
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should never have been able to switch this panel into the multitouch mode.
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However, the firmware presents an other bugs which allowed 6d4f5440
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to counteract the faulty report descriptor. When we request the values
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of the feature 5, the firmware answers "03 03 00". The fields are correct
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but the report id is wrong. Before 6d4f5440, we retrieved all the features
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and injected them in the system. So when we called report 5, we injected
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in the system the report 3 with the values "03 00".
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Setting the second input mode to 03 in this report changed it to "03 03"
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and the touchpad switched to the mt mode. We could have set anything
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in the second field because the actual value (the first 03 in this report)
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was given by the query of report ID 5.
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To sum up: 2 bugs in the firmware were hiding that we were accessing the
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wrong feature.
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Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
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Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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---
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drivers/hid/hid-multitouch.c | 15 +++++++++++++--
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1 file changed, 13 insertions(+), 2 deletions(-)
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diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
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index ba94044cb859..d866720412cd 100644
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--- a/drivers/hid/hid-multitouch.c
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+++ b/drivers/hid/hid-multitouch.c
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@@ -357,8 +357,19 @@ static void mt_feature_mapping(struct hid_device *hdev,
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break;
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}
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- td->inputmode = field->report->id;
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- td->inputmode_index = usage->usage_index;
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+ if (td->inputmode < 0) {
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+ td->inputmode = field->report->id;
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+ td->inputmode_index = usage->usage_index;
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+ } else {
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+ /*
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+ * Some elan panels wrongly declare 2 input mode
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+ * features, and silently ignore when we set the
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+ * value in the second field. Skip the second feature
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+ * and hope for the best.
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+ */
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+ dev_info(&hdev->dev,
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+ "Ignoring the extra HID_DG_INPUTMODE\n");
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+ }
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break;
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case HID_DG_CONTACTMAX:
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--
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2.5.0
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