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/ > +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. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
