Re: Event types

[Jonathan Cameron <jic23@cam.ac.uk>]

On 09/21/10 17:46, Dmitry Torokhov wrote:
> On Sun, Sep 19, 2010 at 06:36:48PM +0100, Jonathan Cameron wrote:
>> Hi All,
>>
>> We are in the process of cleaning up the event subsystem of IIO.
>> As some devices will be used via an input bridge, it makes sense
>> to pin down what they would be translated to in input. Note our
>> 'readings' that will map to events in input are handled via a
>> different patch. There are plenty of drivers to suggest what those
>> should map to. We can basically pretend these devices are joysticks
>> with several xyz controllers.
>>
>> For the sort of direct 'input' types of events - double tap etc
>> we can just copy existing drivers.
>>
>> Much more common for us though are controllable threshold events.
>> In IIO the associated control attributes are named:
>>
>> Like <channel>_<limit>_<dir>_<attr>, where
>>  <channel>: name of the channel, i.e. accel_x0
>>  <limit>:   thresh, mag, roc
>>  <dir>:     rising, falling
>>  <attr>:    en, value, period, mean_period 
>>
>> So taking a typical device (adis16400) we have the following
>> actual events
>>
>> in_supply_thresh_rising
>> in_supply_thresh_falling
>> in_supply_roc_rising
>> in_supply_roc_falling
>>
>> accel_[x|y|z]_thresh_rising
>> accel_[x|y|z]_thresh_falling
>> accel_[x|y|z]_roc_rising
>> accel_[x|y|z]_roc_falling
>>
>> gyro_[x|y|z]_thresh_rising
>> gyro_[x|y|z]_thresh_falling
>> gyro_[x|y|z]_roc_rising
>> gyro_[x|y|z]_roc_falling
>>
>> magn_[x|y|z]_thresh_rising
>> magn_[x|y|z]_thresh_falling
>> magn_[x|y|z]_roc_rising
>> magn_[x|y|z]_roc_falling
>>
>> temp_thresh_rising
>> temp_thresh_falling
>> temp_roc_rising
>> temp_roc_falling
>>
>> in0_thresh_rising
>> in0_thresh_falling
>> in0_roc_rising
>> in0_roc_falling
>>
>> The _mag_ events are for devices (often accelerometers) which provide an
>> interrupt based on the magnitude not the signed value of the relevant channel.
>>
>> Note a typical event only has a value attached to it in the sense that we know
>> what barrier is crossed.
>>
>> So what would such general events map to?  I suppose in some senses they are EV_KEYs
>> but which keys?  The only example I have seen is the adxl34x. That uses btn_touch for
>> tap events and pdata to specify keys for freefall, orientation and activity.
>>
>> In our case I guess the mapping can be provided to the userspace bridge daemon to
>> translate all these events into 'magic' keys. Is this the best plan?
>> A few clearly don't conventionally make much sense in input (temperature and supply
>> voltages would be unusual human interfaces!).
> 
> I think that some of the events do map to key action (taps,
> orientation). This should preferrably be configurable (so it looks like
> we need to plumb EVIOC{S|G}KEYCODE through uinput driver).
Cool, that was what I thought.  Just wanted to check. I guess are going to
need some configuration files in user space to do this. I'll propose that
with a more complete bridge implementation sometime soonish.
 
> Others, such as free fall and activity, are probably not really "keys".
> I'd expect such events be handled by an application completely
> uninterested in other types of keys and other input events, for example
> application that tries to park hard drive in case of fall.
Agreed, these clearly have little to do with human input. Now to wait for
the first person to say there is a game out there where you have to drop
your controller to make the guns fire.... :)
> 
> Unfortunately drivers authors at the moment do not have better interface
> available and thus try to fit it all into input.

Thanks,

Jonathan