From: Jason Gerecke <jason.gerecke@xxxxxxxxx>
In ancient times, an off-by-one-nybble error resulted in the Wacom
driver sending "mangled" tool IDs to userspace. This mangling behavior
was later enshrined into a function so that devices using the then-new
generic codepath could share the same broken behavior. The mangled IDs
have not historically been a major problem for userspace since few
applications care about the exact numeric value of the IDs. As long as
the IDs were unique it didn't much matter. Some programs (cross-
platform and remote-desktop applications in particular) /do/ rely on
the IDs being correct, however.
This patch rids the driver of the mangling behavior.
Signed-off-by: Jason Gerecke <jason.gerecke@xxxxxxxxx>
References: 493630b20389 ("Input: wacom - fix serial number handling on Cintiq 21UX2")
References: 82527da319ee ("HID: wacom: Read and internally use corrected Intuos tool IDs")
---
I'd like to get the opinion of the kernel maintainers on making a
change like this at some point in the future. There are _very_ few
userspace uses of these IDs (primarily: drivers, compositors, and
tablet control panels) and my plan is to update those bits and then
give some time for the changes to roll out to users before re-
submitting this for real. I don't expect any kind of breakage since
we'll be taking our time with the rollout and userspace needs to
have handling for "unknown" IDs anyway (since Wacom periodically
releases new pens).
---
drivers/hid/wacom_wac.c | 18 ++----------------
1 file changed, 2 insertions(+), 16 deletions(-)
diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 2541fa2e0fa3b..facab5bd37e41 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -671,11 +671,6 @@ static int wacom_intuos_pad(struct wacom_wac *wacom)
return 1;
}
-static int wacom_intuos_id_mangle(int tool_id)
-{
- return (tool_id & ~0xFFF) << 4 | (tool_id & 0xFFF);
-}
-
static bool wacom_is_art_pen(int tool_id)
{
bool is_art_pen = false;
@@ -1010,8 +1005,7 @@ static int wacom_intuos_general(struct wacom_wac *wacom)
break;
}
- input_report_abs(input, ABS_MISC,
- wacom_intuos_id_mangle(wacom->id[idx])); /* report tool id */
+ input_report_abs(input, ABS_MISC, wacom->id[idx]); /* report tool id */
input_report_key(input, wacom->tool[idx], 1);
input_event(input, EV_MSC, MSC_SERIAL, wacom->serial[idx]);
wacom->reporting_data = true;
@@ -1379,8 +1373,7 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
input_report_key(pen_input, wacom->tool[0], prox);
input_event(pen_input, EV_MSC, MSC_SERIAL, wacom->serial[0]);
- input_report_abs(pen_input, ABS_MISC,
- wacom_intuos_id_mangle(wacom->id[0])); /* report tool id */
+ input_report_abs(pen_input, ABS_MISC, wacom->id[0]); /* report tool id */
}
wacom->shared->stylus_in_proximity = prox;
@@ -2514,13 +2507,6 @@ static void wacom_wac_pen_report(struct hid_device *hdev,
input_report_key(input, BTN_STYLUS2, wacom_wac->hid_data.barrelswitch2);
input_report_key(input, BTN_STYLUS3, wacom_wac->hid_data.barrelswitch3);
- /*
- * Non-USI EMR tools should have their IDs mangled to
- * match the legacy behavior of wacom_intuos_general
- */
- if (wacom_wac->serial[0] >> 52 == 1)
- id = wacom_intuos_id_mangle(id);
-
/*
* To ensure compatibility with xf86-input-wacom, we should
* report the BTN_TOOL_* event prior to the ABS_MISC or
--
2.46.0
