Re: [PATCH] Input :Added Check for EV_ABS event params

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 21-04-15 23:56, Peter Hutterer wrote:
> On Tue, Apr 21, 2015 at 11:29:16AM -0700, Dmitry Torokhov wrote:
>> Hi Anshul,
>>
>> On Tue, Apr 21, 2015 at 11:19:52AM -0700, Anshul Garg wrote:
>>> From: Anshul Garg <aksgarg1989@gmail.com>
>>>
>>> while handling EV_ABS event in input_handle_abs_event
>>> function added check for out of range event value from
>>> input driver. As input driver sets the ABS params at
>>> registration time so input core should ignore events out
>>> of the range set by the input driver.
>>
>> No, I do not think we want to do that, at least not unconditionally,
>> especially since it is perfectly allowed to use 0 as min/max, which
>> means that exact min and max are not defined. Historically min and max
>> were provided to the userspace as a guidance and it was up to userspace
>> to decide what to do with values outside of the limits.
>
> for the archives:
> X requires us to drop coordinates outside the given range, at least the
> ones we forward to the clients from absolute devices. We have used
> out-of-bounds variables within the synaptics driver in the past though.

Also for the record, for touchpad devices min-max typically give the edges
not the absolute min / max values of the sensor. In some cases there may also
be margins given in the min/max values coming from the touchpad-firmware which
already take an edge-scrolling area into account. So with touchpads getting
values outside of the min/max range is sometimes something which not only
may happen, but actually is expected to happen.

Regards,

Hans