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author | Jason Gerecke <killertofu@gmail.com> | 2021-02-16 22:41:54 +0300 |
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committer | Jiri Kosina <jkosina@suse.cz> | 2021-02-18 11:36:17 +0300 |
commit | 88f38846bfb1a452a3d47e38aeab20a4ceb74294 (patch) | |
tree | 2d80ab6e0cf6357cb28ad3541d1b6a6673ba034d /drivers/hid/hid-input.c | |
parent | b7c20f3815985570ac71c39b1a3e68c201109578 (diff) | |
download | linux-88f38846bfb1a452a3d47e38aeab20a4ceb74294.tar.xz |
HID: wacom: Ignore attempts to overwrite the touch_max value from HID
The `wacom_feature_mapping` function is careful to only set the the
touch_max value a single time, but this care does not extend to the
`wacom_wac_finger_event` function. In particular, if a device sends
multiple HID_DG_CONTACTMAX items in a single feature report, the
driver will end up retaining the value of last item.
The HID descriptor for the Cintiq Companion 2 does exactly this. It
incorrectly sets a "Report Count" of 2, which will cause the driver
to process two HID_DG_CONTACTCOUNT items. The first item has the actual
count, while the second item should have been declared as a constant
zero. The constant zero is the value the driver ends up using, however,
since it is the last HID_DG_CONTACTCOUNT in the report.
Report ID (16),
Usage (Contact Count Maximum), ; Contact count maximum (55h, static value)
Report Count (2),
Logical Maximum (10),
Feature (Variable),
To address this, we add a check that the touch_max is not already set
within the `wacom_wac_finger_event` function that processes the
HID_DG_TOUCHMAX item. We emit a warning if the value is set and ignore
the updated value.
This could potentially cause problems if there is a tablet which has
a similar issue but requires the last item to be used. This is unlikely,
however, since it would have to have a different non-zero value for
HID_DG_CONTACTMAX earlier in the same report, which makes no sense
except in the case of a firmware bug. Note that cases where the
HID_DG_CONTACTMAX items are in different reports is already handled
(and similarly ignored) by `wacom_feature_mapping` as mentioned above.
Link: https://github.com/linuxwacom/input-wacom/issues/223
Fixes: 184eccd40389 ("HID: wacom: generic: read HID_DG_CONTACTMAX from any feature report")
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
CC: stable@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'drivers/hid/hid-input.c')
0 files changed, 0 insertions, 0 deletions