On Monday, January 31, 2011, Kevin Hilman wrote: > Grant Likely <grant.likely@xxxxxxxxxxxx> writes: > > > On Mon, Jan 31, 2011 at 11:16:51PM +0100, Rafael J. Wysocki wrote: > >> On Monday, January 31, 2011, Alan Stern wrote: > >> > On Mon, 31 Jan 2011, Rafael J. Wysocki wrote: > >> > > >> > > On Monday, January 31, 2011, Alan Stern wrote: > >> > > > On Sun, 30 Jan 2011, Rafael J. Wysocki wrote: > >> > > > > >> > > > > > One thing about this implementation is slightly questionable. The new > >> > > > > > power_domain callbacks were added to the __weak platform PM routines, > >> > > > > > which means they will have to be included in every overriding routine > >> > > > > > provided by a platform imiplementation. > >> > > > > > > >> > > > > > Would it be better to separate these things? Have the power_domain > >> > > > > > callbacks occur in a static outer function which then calls a public > >> > > > > > __weak inner function that can be overridden? > >> > > > > > >> > > > > That certainly is a good idea, but I wasn't sure how to do that. It looks > >> > > > > like I could keep the __weak functions as they are and modify > >> > > > > platform_dev_pm_ops instead to point to a new set of function that in turn > >> > > > > would call the __weak ones. For example, the .suspend pointer in > >> > > > > platform_dev_pm_ops might point to a new function, say > >> > > > > platform_pm_full_suspend() that would call the power domain functions and > >> > > > > the "original" platform_pm_suspend(). Is that what you mean? > >> > > > > >> > > > Yes. But what about the platform_bus_set_pm_ops() interface? Should > >> > > > platform-specific replacements for the pm_ops functions also include > >> > > > the power_domain callbacks? > >> > > > >> > > Well, whoever uses platform_bus_set_pm_ops(), he can simply prevent power > >> > > domains from being used by not defining them in the first place. :-) > >> > > >> > But what about the case where the user _does_ want to have power > >> > domains? > >> > >> Ah, OK. The caller of platform_bus_set_pm_ops() will replace the original > >> platform_dev_pm_ops with his own set of operations, so he will not see the > >> power domains. > >> > >> > Do you want to make the replacement routines responsible for > >> > invoking the power-domain callbacks, or should the platform core handle > >> > this automatically? > >> > >> Well, if someone replaces the entire platform_dev_pm_ops object, this means > >> that on his platform power management is substantially different from the > >> generic one. In that case, IMO, he should be responsible for handling all > >> of the subsystem-level aspects of power management, including power domains. > > > > Part of point of doing something like power_domain is to *get rid* of > > platform_bus_set_pm_ops(). It is a horrid, stop-gap interface that > > doesn't scale. I don't think much consideration needs to be made for > > users of platform_bus_set_pm_ops() in this regard. > > As the author of platform_bus_set_pm_ops(), I humbly agree. > > Also, the __weak functions here were obsoleted by > platform_bus_set_pm_ops(). Once Magnus moves to > platform_bus_set_pm_ops() (or this new interface) the __weak attributes > should be removed (c.f. commit log below[1] where > platform_bus_set_pm_ops() was added.) > > Kevin > > commit c64a0926710153b9d44c979d2942f4a8648fd74e > Author: Kevin Hilman <khilman@xxxxxx> > Date: Wed Aug 25 12:50:00 2010 -0700 > > driver core: platform_bus: allow runtime override of dev_pm_ops > > Currently, the platform_bus allows customization of several of the > busses dev_pm_ops methods by using weak symbols so that platform code > can override them. The weak-symbol approach is not scalable when > wanting to support multiple platforms in a single kernel binary. > > Instead, provide __init methods for platform code to customize the > dev_pm_ops methods at runtime. > > NOTE: after these dynamic methods are merged, the weak symbols should > be removed from drivers/base/platform.c. AFAIK, this will only > affect SH and sh-mobile which should be converted to use this > runtime approach instead of the weak symbols. After SH & > sh-mobile are converted, the weak symobols could be removed. > -- So, it seems there are two possibilities, either (1) keep the $subject patch as is in the hope that Magnus will use power domains instead of overriding the __weak callbacks and remove the _weak attribute when that happens, or (2) modify it along the lines suggested by Alan (ie. so that the _weak callbacks stay as they are, but they won't be pointed to by platform_dev_pm_ops directly). I'm pretty much fine with each of them, so I'd prefer to do whichever is generally more useful. Magnus? Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
