Re: [RFC] ACPI table HID/CID allocation

[Udit Kumar <udit.kumar@nxp.com>]

Hi Andrew 
 
> Udit,
> 
> I think it is more like you only need ACPI if you don't have a driver.

Ok, then ACPI or say firmware needs to export AML methods, which are known to OS.

> If it is standard bus with standard drivers the OS code can do power management
> without any help from ACPI. 

In some cases there could be some config registers in IP, which could 
leads to power down mode, then probably power management could be done
without ACPI. 
If we have clock and regulators doing power management,  then ACPI is needed.
No ? 

> In general ACPI exists to abstract chipsets that don't
> have OS drivers, or mother board layout of power plains, GPIOs, etc.

I can think of for power management, without specific driver if such
Power saving is limited to internal SOC.

For example, say temperature of mother board is read using 
some sensor connected with SOC over i2c line. And in SOC
i2c interface is behind some controller.
How do you see to read temperature without having a OS drivers.
For power management based on  temperature, we may not need a
driver.


Thanks,
 Udit