Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [RFC][PATCH] Power domains for platform bus type | Date | Tue, 1 Feb 2011 00:10:45 +0100 |
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On Monday, January 31, 2011, Grant Likely wrote: > On Sun, Jan 30, 2011 at 01:07:19AM +0100, Rafael J. Wysocki wrote: > > Hi, > > > > This is something we discussed during the last Linux Plumbers Conference. > > > > The problem appears to be that the same device may be used in different > > systems in different configurations such that actions necessary for the > > device's power management can vary from one system to another. In those > > cases the drivers' power management callbacks are generally not sufficient, > > because they can't take the configuration of the whole system into account. > > > > I think this issue may be addressed by adding objects that will represent > > power domains and will provide power management callbacks to be executed > > in addition to the device driver's PM callbacks, which is done by the patch > > below. > > > > Please have a look at it and tell me what you think. > > In general it looks okay. I agree with Alan's comment that it > probably belongs outside the platform device pm ops. It's the sort of > thing that should be available to *any* device, regardless of bus > type.
I'd rather say any subsystem. Anyway, I'm not sure how many subsystems will find it useful at the core level except for platform.
> ie. it is conceivable that some spi and i2c devices would be in > need to be in the same power_domain.
So there's spi and i2c. Anything else?
> It slightly worries me about the amount of code required to manage all the > nested levels of pm_ops. I wonder if there is a better way to manage > them.
I'm not really sure. The amount of code is kind of proportional to the number of different callbacks in struct dev_pm_ops ...
> Also, what is the use case for having 2 sets of power_domain ops? My > gut tells me that you'd only want to do post ops on the > {freeze,suspend,poweroff} path and pre ops on the {resume,thaw,restore} > path. It seems overly engineered to me, but I may be missing > something fundamental.
Well, that's a part of the RFC, actually. :-)
For the subsystems I've worked with (PCI, ACPI, PNP to some extent) one set would be sufficient, but I don't know of every possible use case.
Thanks, Rafael
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