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

[Alex Courbot]

On Thu 02 Aug 2012 05:45:41 PM JST, Thierry Reding wrote:
> * PGP Signed by an unknown key
>
> 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:
> > > > Old Signed by an unknown key
> > >
> > > On Thu, Aug 02, 2012 at 05:00:13PM +0900, Alex Courbot wrote:
> > > > On 07/31/2012 07:45 AM, Stephen Warren wrote:
> > > > > 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.

Probably not worth to try this then?

Alex.
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