[maemo-users] [maemo-users] Secret sensor..

From: Nils Faerber nils.faerber at kernelconcepts.de
Date: Mon Oct 24 15:46:21 EEST 2005
Hash: SHA1

Jan Wildeboer schrieb:
> Tom Rathbone wrote:
>> Does anyone know anything more about it?  What sensor
>> is used? How is this event handled in software?
> My educated guess is that this is a simple reed-switch connected to a
> keyboard event that initiates some ACPI stuff.
> Not really rocket science ...

Not really, except that it is for sure no ACPI stuff...
ACPI, as well as APM, is x86 only and will probably always be. Reason
for this is that ACPI is implemented in the BIOS of the machine while
embedded systems usually have very specialised power management
implemented in the kernel and its drivers.

ACPI is intended to be a standard for non standard hardware - shall
read, not all PCs are the same but through ACPI they do look the same.
For embedded systems ACPI would mean a huge overhead.

The Linux kernel 2.6 has a nice power management interface so that
drivers can nicely attach various power management callback functions.
So for this alone no ACPI or such is needed.

Besides, it could also be a hall sensor (changing electrical resistance
proportional to statig magnetic field)... :)

> Jan Wildeboer
  nils faerber

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