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Commit d9ca1c99 authored by Benjamin Tissoires's avatar Benjamin Tissoires Committed by Jiri Kosina
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Input: reserve 2 events code because of HID 



Prior to commit 190d7f02 ("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: default avatarBenjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent 5fe2ccbe

include/uapi/linux/input-event-codes.h

+18 −1
Original line number Diff line number Diff line
@@ -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) */