path: root/drivers/hid/wacom_wac.c
diff options
authorJason Gerecke <killertofu@gmail.com>2021-02-16 11:41:54 -0800
committerJiri Kosina <jkosina@suse.cz>2021-02-18 09:36:17 +0100
commit88f38846bfb1a452a3d47e38aeab20a4ceb74294 (patch)
tree2d80ab6e0cf6357cb28ad3541d1b6a6673ba034d /drivers/hid/wacom_wac.c
parentb7c20f3815985570ac71c39b1a3e68c201109578 (diff)
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/wacom_wac.c')
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 1bd0eb71559c..44d715c12f6a 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -2600,7 +2600,12 @@ static void wacom_wac_finger_event(struct hid_device *hdev,
wacom_wac->is_invalid_bt_frame = !value;
- features->touch_max = value;
+ if (!features->touch_max) {
+ features->touch_max = value;
+ } else {
+ hid_warn(hdev, "%s: ignoring attempt to overwrite non-zero touch_max "
+ "%d -> %d\n", __func__, features->touch_max, value);
+ }