Calling all hotkey expertise...

[Herton Ronaldo Krzesinski]

Em Qui, 2011-02-10 às 21:00 +0000, Colin Ian King escreveu:
> Hi there,
> 
> I'm pulling together a document with Tony Espy on a BIOS recommendations
> guide. I'm really interested in any documents, links, and helpful info
> on how hotkeys work.  It is a non-trivial issue and there are many
> different ways it is implemented.  

From what I remember and from experience (correct me if I say something
wrong), vendors usually implement hotkeys:
- using a WMI interface, where a driver needs to be written. The driver
receives a WMI notification and calls wmi_evaluate_method (WMXX) to get
the response/data so if the event is a hotkey it gets a code and
translates it to input layer. It's a lot easier if the vendor gives
information on its WMI implementation, as by nature of ACPI-WMI every
vendor can choose what parameters/format to accept on WMI methods etc.
- using a vendor specific device HID. The vendor implements its own acpi
device in DSDT, with a HID name it choses. A specific platform driver
needs to be written too. Methods and way to work with this device are
totally defined by the vendor. One example is topstar_laptop in the
kernel. Also it's easier if vendor gives info/spec on every aspect of
what it implemented in BIOS/dsdt, otherwise we have to discover by
reading DSDT and do experiments (trial and error).
- sending codes directly via the keyboard controller (so implemented
directly in embedded controller, also some people call it as keyboard
bios, but anyway I think should be on ec firmware). So kernel directly
receive keyboard codes on keyboard input device, no need to extra
driver, but many times the codes have to be remaped on user space to the
real key code meaning/value (udev keymaps)

It seems we already have some documentation on this:
https://wiki.edubuntu.org/Hotkeys/Architecture

Also there are cases of some hotkeys where the Vendor implements it on
BIOS or let the OS control it:
- Brightness keys
some vendors put brightness handling on bios, but if the system reports
as being Windows Vista or newer via acpi_os (which Linux does), it
disables its brightness handling and let OS do it, so sometimes you have
to pass acpi_osi="!Windows 2006" on kernel command line to brightness
keys to work.
- Video output switch
only on newer bioses, and same as brightness keys, but bios disables its
handling only if system is Windows 7 or newer, so you have to pass
acpi_osi="!Windows 2009" on kernel command line.
This is because recommendation Microsoft does to the vendors. I don't
fully understand it, but the acpi_osi parameters make the bios take
control again and are workarounds.

> 
> If you have *any* useful info, please can you forward it to me.  I may
> even get around to compiling it all into a Wiki page.
> 
> Thanks!
> 
> Colin
> -- 
> Colin King 
> Hardware Enablement Team - Kernel Team - Platform Team - Canonical
> Ubuntu - Linux for human beings | www.ubuntu.com | www.canonical.com
> 
> 

-- 
[]'s
Herton