On Thursday, July 06, 2017 05:17:50 AM Pavel Machek wrote:

On Sun 2017-07-16 01:29:57, Rafael J. Wysocki wrote:

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On Saturday, July 15, 2017 06:46:26 PM Pavel Machek wrote:

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Hi!

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I had an idea of using an enum type encompassing all of the power states
defined for various platforms and serving both as a registry (to ensure the
uniqueness of the values assigned to the states) and a common ground
between platforms and drivers.

Something like:

enum platform_target_state {
	PLATFORM_STATE_UNKNOWN = -1,
	PLATFORM_STATE_WORKING = 0,
	PLATFORM_STATE_ACPI_S1,
	PLATFORM_STATE_ACPI_S2,
	PLATFORM_STATE_ACPI_S3,
	PLATFORM_STATE_MY_BOARD_1_GATE_CLOCKS,
	PLATFORM_STATE_MY_BOARD_1_GATE_POWER,
	PLATFORM_STATE_ANOTHER_BOARD_DO_CRAZY_STUFF,
	...
};

and define ->target_state to return a value of this type.

Then, if a driver sees one of these and recognizes that value, it should
know exactly what to do.

Remind me why this is good idea?

Because there are drivers that need to do specific things during
suspend on a specific board when it goes into a specific state as a
whole.

We have seen driver that cares about voltage to his device being
lost. That's reasonable.

Inquiring what the platform target state is... is not.

So why exactly isn't it reasonable?

Please use technical arguments.  Saying that something is wrong without
explaining the problem you see with it isn't particulatly useful in technical
discussions.

Deep in your heart, you should know that having enum listing all the platforms linux
runs on is a very bad idea.

Even so, if I'm unable to explain to people why this is a bad idea in technical
terms, that doesn't mean too much.

I actually noticed an issue with the approach that I missed before, see my last
reply to Florian.

Anyway, there are better solutions, regulator framework already knows if given rail
will be powered off or not, and their driver already knows if they are going
suspend/standby. They just need to use existing interfaces.

So they need to know what has been passed to suspend_devices_and_enter()
anyway and currently there's no interface for that.  That actually is the source
of the whole issue.

Thanks,
Rafael