On Tuesday, July 30, 2013 07:43:48 AM Aaron Lu wrote:

On 07/30/2013 06:21 AM, Rafael J. Wysocki wrote:

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On Monday, July 29, 2013 10:09:53 PM Aaron Lu wrote:

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On 07/27/2013 09:10 PM, Rafael J. Wysocki wrote:

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From: Rafael J. Wysocki <redacted>

Make acpi_device_set_power() check if the given device is power
manageable before checking if the given power state is valid for that
device.  Otherwise it will print that "Device does not support" that
power state into the kernel log, which may not make sense for some
power states (D0 and D3cold are supported by all devices by
definition).

It will not print "Device does not support" that power state if that
power state is D0 or D3cold since we have unconditionally set those two
power state's valid flag.

So you didn't actually looked at acpi_bus_get_power_flags() that set the
power.states[].flags.valid flag, because If you had looked at it, you would
have seen that that's not the case.

No, we don't set the valid flag for devices that aren't power manageable
(i.e. have flags.power_manageable unset), which is the *whole* *point* of
this change.

Right, I missed this. Sorry for the noise.

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OTOH, what value should we return for a device node that is not power
manageable in acpi_device_set_power when the target state is D0 or D3
cold? The old behavior is to return 0, meanning success without taking
any actual action.

In acpi_bus_set_power, if the device is not power manageable, we will
return -ENODEV; in acpi_dev_pm_full/low_power, we will return 0 as in
the original acpi_device_set_power. So return -EINVAL here is correct?

No, the original acpi_device_set_power() will return -ENODEV then, but
in my opinion returning -EINVAL is more accurate, because "power
manageable" means "you can change power state of it".

Shall I prepare a patch to update the errno in acpi_bus_set_power?

In fact, it doesn't need to check flags.power_manageable after this patch
and the debug message won't be missed I think, so please just remove
the whole if () from there, if that's not a problem.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.