On Thu, Oct 04, 2018 at 02:34:30PM +0200, Benjamin Tissoires wrote:
> Prior to commit 190d7f02ce8e ("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@xxxxxxxxxx>
> ---
>
> Dmitry, I did not take your Acked-by, as I added 2 new events and wanted to
> be sure you are still OK.
Yes, this is still fine.
Acked-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
>
> Jiri, this will still need to go through your tree, as the input-event-codes
> changes that introduce REL_WHEEL_HI_RES are in your for-4.20/logitech-highres.
>
> Cheers,
> Benjamin
>
> include/uapi/linux/input-event-codes.h | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h
> index 29fb891ea337..b5e0e9856c47 100644
> --- a/include/uapi/linux/input-event-codes.h
> +++ b/include/uapi/linux/input-event-codes.h
> @@ -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) */
> --
> 2.14.3
>
--
Dmitry
