Re: [RFC][PATCH v3 1/3] runtime interpreted power sequences

On Thu, Aug 02, 2012 at 05:27:44PM +0900, Alex Courbot wrote:

On Thu 02 Aug 2012 05:21:57 PM JST, Thierry Reding wrote:

quoted

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On Thu, Aug 02, 2012 at 05:00:13PM +0900, Alex Courbot wrote:

quoted

On 07/31/2012 07:45 AM, Stephen Warren wrote:

quoted

Oh I see. That's a little confusing. Why not just reference the relevant
resources directly in each step; something more like:

	gpio@1 {
		action = "enable-gpio";
		gpio = <&gpio 1 0>;
	};

I guess that might make parsing/building a little harder, since you'd
have to detect when you'd already done gpio_request() on a given GPIO
and not repeat it or something like that, but to me this makes the DT a
lot easier to comprehend.

I tried to move towards having the phandles directly in the
sequences themselves - that reminded me why I did not do that in the
first place. Let's say we have a sequence like this (reg property
omitted on purpose):

power-on-sequence {
	step@0 {
		regulator = <&backlight_reg>;
		enable;
	};
	step@1 {
		delay = <10000>;
	};
	step@2 {
		pwm = <&pwm 2 5000000>;
		enable;
	};
	step@3 {
		gpio = <&gpio 28 0>;
		enable;
	};
};

The problem is, how do we turn these phandles into the resource of
interest. The type of the resource can be infered by the name of the
property. The hard part is resolving the resource from the phandle -
it seems like the API just does not allow to do this. GPIO has
of_get_named_gpio, but AFAIK there are no equivalent for regulator
consumer and PWM: the only way to use the DT with them is through
get_regulator and get_pwm which work at the device level.

Or is there a way that I overlooked?

No, you are right. Perhaps we should add exported functions that do the
equivalent of of_pwm_request() or the regulator_dev_lookup() and
of_get_regulator() pair.

How would that be looked with respect to "good DT practices"? I can
somehow understand the wish to restrain DT access to these functions
that integrate well with current workflows. Aren't we going to be
frowned upon if we make more low-level functions public?

Yes, I think that's exactly what will happen.

Thierry