linuxconsole-dev

writing a keyboard driver

[Justin C. <jp...@do...>]

I am just sitting down to write a kernel module for an Apple Newton serial
keyboard,a nd I am slightly confused by the terminology about scancodes.

1.7 The keycode, keycodemax, keycodesize fields
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These two fields will be used for any inpur devices that report their data
as scancodes. If not all scancodes can be known by autodetection, they may
need to be set by userland utilities. The keycode array then is an array
used to map from scancodes to input system keycodes. The keycode max will
contain the size of the array and keycodesize the size of each entry in it
(in bytes).

What does this actually mean? Should I use this? Could someone just quickly
explain...


Justin

Re: writing a keyboard driver

[James S. <jsi...@su...>]

> I am just sitting down to write a kernel module for an Apple Newton serial
> keyboard,a nd I am slightly confused by the terminology about scancodes.
> 
> 1.7 The keycode, keycodemax, keycodesize fields
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> These two fields will be used for any inpur devices that report their data
> as scancodes. If not all scancodes can be known by autodetection, they may
> need to be set by userland utilities. The keycode array then is an array
> used to map from scancodes to input system keycodes. The keycode max will
> contain the size of the array and keycodesize the size of each entry in it
> (in bytes).

Scancodes are what are generated by the hardware. If you press a 7 on
say a alpha you might get a code from hardware of say 34. On a PC you
get a value of 117. The input system has a bunch of defined values for
specific keys. So if you are reading /dev/eventX and you get KEY_7 this
means you press a 7 no matter what the value was the hardware generated. 
Each input driver has a keycode array to perform this mapping which
basically goes from hardware specific codes to universal
codes. keycode_max is the size of the array which is the maximum number of 
keys that can generate codes times what the size of the each field 
(keycodesize).