Messages in this thread | | | Date | Wed, 1 Aug 2012 10:47:39 +0900 | From | Alex Courbot <> | Subject | Re: [RFC][PATCH v3 1/3] runtime interpreted power sequences |
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On 07/31/2012 09:55 PM, Mitch Bradley wrote: > On 7/31/2012 8:38 PM, Thierry Reding wrote: >> On Tue, Jul 31, 2012 at 08:22:17PM +0800, Mitch Bradley wrote: >>> On 7/31/2012 6:56 PM, Thierry Reding wrote: >>>> On Tue, Jul 31, 2012 at 07:32:20PM +0900, Alex Courbot wrote: >>>>> On 07/31/2012 07:45 AM, Stephen Warren wrote: >>>>>> I wonder if using the same structure/array as input and output would >>>>>> simplify the API; the platform data would fill in the fields mentioned >>>>>> above, and power_seq_build() would parse those, then set other fields in >>>>>> the same structs to the looked-up handle values? >>>>> >>>>> The thing is that I am not sure what happens to the platform data >>>>> once probe() is done. Isn't it customary to mark it with __devinit >>>>> and have it freed after probing is successful? >>>> >>>> No, platform data should stay around forever. Otherwise, consider what >>>> would happen if your driver is built as a module and you unload and load >>>> it again. >>>> >>>>> More generally, I think it is a good practice to have data >>>>> structures tailored right for what they need to do - code with >>>>> members that are meaningful only at given points of an instance's >>>>> life tends to be more confusing. >>>> >>>> I agree. Furthermore the driver unload/reload would be another reason >>>> not to reuse platform data as the output of the build() function. >>>> >>>> But maybe what Stephen meant was more like filling a structure with data >>>> taken from the platform data and pass that to a resolve() function which >>>> would fill in the missing pieces like pointers to actual resources. I >>>> imagine a managed interface would become a little trickier to do using >>>> such an approach. >>>> >>>>>> If the nodes have a unit address (i.e. end in "@n"), which they will >>>>>> have to if all named "step" and there's more than one of them, then they >>>>>> will need a matching reg property. Equally, the parent node will need >>>>>> #address-cells and #size-cells too. So, the last couple lines would be: >>>>>> >>>>>> power-on-sequence { >>>>>> #address-cells = <1>; >>>>>> #size-cells = <0>; >>>>>> step@0 { >>>>>> reg = <0>; >>>>> >>>>> That's precisely what I would like to avoid - I don't need the steps >>>>> to be numbered and I certainly have no use for a reg property. Isn't >>>>> there a way to make it simpler? >>>> >>>> It's not technically valid to not have the reg property. Or >>>> #address-cells and #size-cells properties for that matter. >>> >>> I'm not keen on this representation where individual steps are nodes. >>> That seems like it could end up being too "heavyweight" for a long sequence. >> >> The other alternative would involve using a single property to encode >> one sequence. I think that was the initial proposal, though using proper >> phandle encoding it could probably be enhanced a bit. However anything >> that involves a single property has the problem that we need to encode >> the type of resource as an integer, and that makes things very hard to >> read. >> >> So it would look something like this: >> >> power-on = <1 &gpio 6 0 1 >> 0 10000 >> 2 ® 1 >> 3 &pwm 0 5000000 1>; >> >> power-off = <3 &pwm 0 5000000 0 >> 2 ® 0 >> 0 10000 >> 1 &gpio 6 0 0>; >> >> So the first cell would encode the type: >> 0: delay >> 1: gpio >> 2: regulator >> 3: PWM >> >> The next n cells would be the phandle and the specifier, while the last >> cell would encode a resource-specific parameter: >> delay: time in microseconds >> gpio: set level (0: low, 1: high) >> regulator: 0: disable, 1: enable >> pwm: 0: disable, 1: enable >> >> I guess this would be more compact, but it is also very hard to read. Is >> that something you would be happier with? Perhaps you were thinking of >> something completely different? > > > Perhaps a compact/flexible encoding could be designed, with a textual > encoding that is easy to read. A separate tool could convert the text > encoding to the integer format, annotated with comments containing > the "source text". A file containing that output could be #included > into the dts file.
Do you mean having a external compiler that would run before dtc just for producing the power sequences? That sounds a little bit overkill for something that ough to remain simple.
Also, although I admit I don't have the whole picture of where they could be used, I don't expect the power sequences to grow to sizes that would make us bother about their footprint.
Alex.
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