On Monday, February 14, 2011, Alan Stern wrote: > On Sat, 12 Feb 2011, Rafael J. Wysocki wrote: > > > From: Rafael J. Wysocki <rjw@xxxxxxx> > > > > The code handling system-wide power transitions (eg. suspend-to-RAM) > > can in theory execute callbacks provided by the device's bus type, > > device type and class in each phase of the power transition. In > > turn, the runtime PM core code only calls one of those callbacks at > > a time, preferring bus type callbacks to device type or class > > callbacks and device type callbacks to class callbacks. > > > > It seems reasonable to make them both behave in the same way in that > > respect. Moreover, even though a device may belong to two subsystems > > (eg. bus type and device class) simultaneously, in practice power > > management callbacks for system-wide power transitions are always > > provided by only one of them (ie. if the bus type callbacks are > > defined, the device class ones are not and vice versa). Thus it is > > possible to modify the code handling system-wide power transitions > > so that it follows the core runtime PM code (ie. treats the > > subsystem callbacks as mutually exclusive). > > > > On the other hand, the core runtime PM code will choose to execute, > > for example, a runtime suspend callback provided by the device type > > even if the bus type's struct dev_pm_ops object exists, but the > > runtime_suspend pointer in it happens to be NULL. This is confusing, > > because it may lead to the execution of callbacks from different > > subsystems during different operations (eg. the bus type suspend > > callback may be executed during runtime suspend, while the device > > type callback will be executed during runtime resume). > > > > Make all of the power management code treat subsystem callbacks in > > a consistent way, such that: > > (1) If the device's bus type is defined (eg. dev->bus is not NULL) > > and its pm pointer is not NULL, the callbacks from dev->bus->pm > > will be used. > > (2) If dev->bus is NULL or dev->bus->pm is NULL, but the device's > > device type is defined (eg. dev->type is not NULL) and its pm > > pointer is not NULL, the callbacks from dev->type->pm will be > > used. > > (3) If dev->bus is NULL or dev->bus->pm is NULL and dev->type is > > NULL or dev->type->pm is NULL, the callbacks from dev->class->pm > > will be used provided that both dev->class and dev->class->pm > > are not NULL. > > It looks okay, but I haven't tested it. Just one minor change needed > in the documentation: > > > +All phases use bus, type, or class callbacks (that is, methods defined in > > +dev->bus->pm, dev->type->pm, or dev->class->pm). These callbacks are mutually > > +exclusive, so if the bus provides a struct dev_pm_ops object pointed to by its > > +pm field (i.e. both dev->bus and dev->bus->pm are defined), the callbacks > > +included in that object (i.e. dev->bus->pm) will be used. In turn, if the > > s/In turn/Otherwise/ OK > > +device type provides a struct dev_pm_ops object pointed to by its pm field > > +(i.e. both dev->type and dev->type->pm are defined), the PM core will used the > > +callbacks from that object (i.e. dev->type->pm). Finally, if the pm fields of > > +both the bus and device type objects are NULL (or those objects do not exist), > > +the callbacks provided by the class (that is, the callbacks from dev->class->pm) > > +will be used. > > > > These callbacks may in turn invoke device- or driver-specific methods stored in > > dev->driver->pm, but they don't have to. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
