hid-multitouch omits the last touch usage when completing a slot under certain scenarios |
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Issue description
According to [1] and also seemingly agreed by [2], the Scan Time usage (0x0D 0x56) of a touch device is a report level usage, not a contact level usage.
Commit 29cc309d8bf19 ("HID: hid-multitouch: forward MSC_TIMESTAMP") [3] added handling of the Scan Time usage (0x0D 0x56) in the hid-multitouch kernel driver. However, it 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).
[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/
[3] https://patchwork.kernel.org/patch/9914039/
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May 30 2018
The following revision refers to this bug: https://chrome-internal.googlesource.com/chromeos/platform/experimental-touch-fw/+/79e20c36c7481bf2bb1d0162a75fde2bafafd536 commit 79e20c36c7481bf2bb1d0162a75fde2bafafd536 Author: Ben Chan <benchan@chromium.org> Date: Wed May 30 19:50:52 2018
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May 31 2018
The following revision refers to this bug: https://chromium.googlesource.com/chromiumos/third_party/kernel/+/151f31d1bbbc58456ec8ced5db36b775f31a5dc2 commit 151f31d1bbbc58456ec8ced5db36b775f31a5dc2 Author: Ben Chan <benchan@chromium.org> Date: Thu May 31 10:50:22 2018 BACKPORT: HID: multitouch: fix calculation of last slot field in multi-touch reports 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. [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@chromium.org> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz> (backported from commit abb36fe691b28f2a64926b61448d6b9610ed879a in https://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid.git for-4.18/multitouch branch) BUG= chromium:847561 TEST=Verified with the latest eve touchpad firmware, which includes the Scan Time usage in touch input reports. Change-Id: Id4ea83fce008b5e1b3bb06a84f9f7ef69f9e8283 Signed-off-by: Ben Chan <benchan@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/1077590 Reviewed-by: Dmitry Torokhov <dtor@chromium.org> [modify] https://crrev.com/151f31d1bbbc58456ec8ced5db36b775f31a5dc2/drivers/hid/hid-multitouch.c
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May 31 2018
The following revision refers to this bug: https://chromium.googlesource.com/chromiumos/third_party/kernel/+/176bf8e3de91ba004f684b63d7a49eacf7e29db4 commit 176bf8e3de91ba004f684b63d7a49eacf7e29db4 Author: Ben Chan <benchan@chromium.org> Date: Thu May 31 19:26:14 2018 BACKPORT: HID: multitouch: fix calculation of last slot field in multi-touch reports 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. [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@chromium.org> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz> (backported from commit abb36fe691b28f2a64926b61448d6b9610ed879a in https://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid.git for-4.18/multitouch branch) BUG= chromium:847561 TEST=Verified with the latest eve touchpad firmware, which includes the Scan Time usage in touch input reports. Change-Id: Id4ea83fce008b5e1b3bb06a84f9f7ef69f9e8283 Signed-off-by: Ben Chan <benchan@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/1077011 Reviewed-by: Dmitry Torokhov <dtor@chromium.org> [modify] https://crrev.com/176bf8e3de91ba004f684b63d7a49eacf7e29db4/drivers/hid/hid-multitouch.c
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May 31 2018
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Comment 1 by benchan@chromium.org
, May 30 2018