Re: Generic interface for accelerometers (AMS, HDAPS, ...)

[Vojtech Pavlik]

On Wed, Jul 05, 2006 at 05:59:29PM -0600, Robert Hancock wrote:
> Henrique de Moraes Holschuh wrote:
> >HDAPS talks to the embedded controller using IO over the LPC bus, and not 
> >to
> >the accelerometer chip or to a simple A/D i2c chip which is used excusively
> >for accelerometer access.  The EC interface for HDAPS data retrieval is
> >not friendly to any errors, and hardlocks the machine somehow if any
> >firmware bugs hit or if we violate any of the rules (that are not written
> >anywhere) about how to access the EC without geting the SMBIOS unhappy.
> >
> >So, turning off HDAPS polling while it is not necessary really looks like a
> >good idea overall.
> >
> >We are investigating the ACPI global lock as a way to at least get the
> >SMBIOS to stay away from the EC while we talk to it, but we don't know if
> >the entire SMBIOS firmware respects that lock.
> 
> It had better, that is exactly what the ACPI Global Lock is supposed to 
> prevent (concurrent access to non-sharable resources between the OS and 
> SMI code). The ACPI DSDT contains information on whether or not the 
> machine requires the Global Lock in order to access the EC or whether it 
> is safe to access without locking.
 
Isn't that vaild only if you actully use ACPI to access the EC? (AFAIK
the HDAPS driver does direct port access.)

-- 
Vojtech Pavlik
Director SuSE Labs
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