On Fri, 2012-11-09 at 11:41 -0500, Alan Stern wrote: > On Fri, 9 Nov 2012, Huang Ying wrote: > > > On Thu, 2012-11-08 at 12:07 -0500, Alan Stern wrote: > > > On Thu, 8 Nov 2012, Rafael J. Wysocki wrote: > > > > > > > > > > is it a good idea to allow to set device state to SUSPENDED if > > > > > > > the device > > > > > > > is disabled? > > > > > > > > > > > > No, it is not. The status should always be ACTIVE as long as > > > > > > usage_count > 0. > > > > > > That isn't strictly true, because pm_runtime_get_noresume violates this > > > rule. What the PM core actually does is prevent a transition from the > > > ACTIVE state to the SUSPENDING/SUSPENDED state if usage_count > 0, > > > _provided_ runtime PM is enabled. There's no such restriction when it > > > is disabled. > > > > Usage count may be not a issue for the end user. But "on" in "control" > > sysfs file + SUSPENDED can be confusing for the end user. Maybe we need > > to check dev->power.runtime_auto in pm_runtime_set_suspended(). > > You are confusing the issue by raising two separate (though related) > questions.
Thanks for clarify. > The first question: How should the PCI subsystem prevent the parents of > driverless VGA devices from being runtime suspended while userspace is > accessing them? I think Rafael's patch is good for that. > The second question: Should the PM core allow devices that are disabled > for runtime PM to be in the SUSPENDED state when > dev->power.runtime_auto is clear? I think that should not be allowed. > Assuming we don't want to allow this, there's a third question: Should > pm_runtime_allow call pm_runtime_set_suspended if the device is > disabled? Is it absolute necessary to call pm_runtime_set_suspended? If the device is disabled, the transition to SUSPENDED state will not be triggered even if the device is ACTIVE. Best Regards, Huang Ying -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
