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Input: reserve 2 events code because of HID

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Prior to commit 190d7f02ce ("HID: input: do not increment usages when
a duplicate is found") from the v4.18 kernel, HID used to shift the
event codes if a duplicate usage was found. This ended up in a situation
where a device would export a ton of ABS_MISC+n event codes, or a ton
of REL_MISC+n event codes.

This is now fixed, however userspace needs to detect those situation.
Fortunately, ABS_MT_SLOT-1 (ABS_MISC+6) was never assigned a code, and
so libinput can detect fake multitouch devices from genuine ones by
checking if ABS_MT_SLOT-1 is set.

Now that we have REL_WHEEL_HI_RES, libinput won't be able to differentiate
true high res mice from some other device in a pre-v4.18 kernel.

Set in stone that the ABS_MISC+6 and REL_MISC+1 are reserved and should not
be used so userspace can properly work around those old kernels.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Benjamin Tissoires 2018-10-04 14:34:30 +02:00 committed by Jiri Kosina
parent 5fe2ccbef9
commit d9ca1c990a
1 changed files with 18 additions and 1 deletions
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19
include/uapi/linux/input-event-codes.h
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@ -708,7 +708,15 @@
#define REL_DIAL 0x07
#define REL_WHEEL 0x08
#define REL_MISC 0x09
#define REL_WHEEL_HI_RES 0x0a
/*
* 0x0a is reserved and should not be used in input drivers.
* It was used by HID as REL_MISC+1 and userspace needs to detect if
* the next REL_* event is correct or is just REL_MISC + n.
* We define here REL_RESERVED so userspace can rely on it and detect
* the situation described above.
*/
#define REL_RESERVED 0x0a
#define REL_WHEEL_HI_RES 0x0b
#define REL_MAX 0x0f
#define REL_CNT (REL_MAX+1)
@ -745,6 +753,15 @@
#define ABS_MISC 0x28
/*
* 0x2e is reserved and should not be used in input drivers.
* It was used by HID as ABS_MISC+6 and userspace needs to detect if
* the next ABS_* event is correct or is just ABS_MISC + n.
* We define here ABS_RESERVED so userspace can rely on it and detect
* the situation described above.
*/
#define ABS_RESERVED 0x2e
#define ABS_MT_SLOT 0x2f /* MT slot being modified */
#define ABS_MT_TOUCH_MAJOR 0x30 /* Major axis of touching ellipse */
#define ABS_MT_TOUCH_MINOR 0x31 /* Minor axis (omit if circular) */