HAL FDI matched Buttons

[Richard Hughes]

I know we touched on this a bit before, and after some discussion with a
few other people, I wanted some feedback from the list.

Custom buttons to actions is very laptop model specific. Matthew Garrett
has already done lots of work with hotkey-setup using XTEST on ubuntu,
but admits doing doing it this way is a bit of a hack.

Instead of writing .ht files that have the format:

# Help key
setkeycodes e025 168

and then letting a file read those in and parse them, and then monitor
the scancodes and/or acpi events, I propose that we have a simple fdi
file per-vendor, or per-model so that we can:

* Unify all the button handling stuff there is now
* Perhaps use a uinput kernel side input device for maximum
compatibility (or just send a dbus DeviceCondition).
* Only match on specific laptop models (using the existing fdi
framework) -- in that way manufacturers can just ship one FDI file that
maps all the custom buttons to normal actions, e.g. logout.
* Have generic button object that issues the correct type of output.

For instance, one fdi file could map the alt-f4 key to the scancode for
HELP, so that the image on the button matches the action. This would
only be done for the system.vendor = VENDOR.

In this way HAL can have a whole load of generic button objects that
have a specific type. All the key types could be monitored in a single
hal-addon.

One specific question, can a HAL addon 'create' a new device, or can it
just merge specific data items? How should new button devices be
generated?

Ideas, and comments welcome.

Richard.