Re: iio A/D converter input to input event subsystem

[Alexandre Belloni <alexandre.belloni@free-electrons.com>]

Hi Robert,

On 02/08/2014 at 13:14:30 -0500, gmane@reliableembeddedsystems.com wrote :
> Hi,
> 
> I would like to use a couple of resistors and keys and one Analog
> input[1], read the analogue voltage from a kernel driver, figure out
> which key is pressed and pass this on to the Linux input subsystem.
> (Am I really the only one with this use case?)
> 
> In my specific case it's about a beagle bone black, which means that
> the A/D driver is an iio adc driver[2].
> 
> How would it be possible to reuse the iio A/D converter driver code
> for my driver? Maybe it would even be possible to create something
> more generic so iio A/D converter channels could be used as input
> keys. Some sample code which would enable me to choose an analog
> input and read from it from kernel space would help me to write some
> basic sample driver, I guess.
> 
> The reason I would like to write a device driver instead of a user
> space application is mainly the input subsystem. From the user space
> application's point of view utilizing a device driver which feeds
> the input subsystem would make it easy to exchange what's underneath
> without user space even noticing. (keys to Input pins, a key matrix
> to I/O pins, i2c input, A/D converter,...).
> 

Did you have a look at uinput? This would allow you to inject input
events after processing the ADC values in userspace.

Simple example: http://thiemonge.org/getting-started-with-uinput

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com