input: it8xxx2_kbd: add a kso-ignore-mask property

[fabiobaltieri]

The it8xxx2_kbd KSO pins can be used as both keyboard scan and GPIO. By default the keyboard scanning driver controls the output level of all the KSO signals from 0 to (col-size - 1), meaning that any line in between used as GPIO is going to have its output value overridden.

Add a kso-ignore-mask property to the keyboard scan driver to allow specifiying extra pins that should not be controlled by the driver.

[Dino-Li]

Since we also set keyboard scan output registers in it8xxx2_kbd_init() function, please introduce the property into the function.

[fabiobaltieri]

Since we also set keyboard scan output registers in it8xxx2_kbd_init() function, please introduce the property into the function.

Good point, thanks for spotting it. Done.

[bjarki-andreasen]

I personally prefer whitlisting signals rather than blacklisting everything else :) a default of 0xFFFF would be backwards compatible as well. Both solutions work though :)

[fabiobaltieri]

I personally prefer whitlisting signals rather than blacklisting everything else :) a default of 0xFFFF would be backwards compatible as well. Both solutions work though :)

Interesting observation, this is for a bit of a hyper specific corner case that I'd be shocked if anyone else care about (we are messing with column 2... don't ask), it's just one bit so easier to read in the current form, plus the high significant ones are already left alone, depending on what col-size is set to, and in that case leaving other bits sets when they are not normally touch them may give the impression that they have to be cleared when they are not. Am I overthinking it? I'm probably overthinking it.