On Fri, Jun 27, 2014 at 02:27:28PM -0400, Alan Stern wrote: > On Wed, 25 Jun 2014, Rafael J. Wysocki wrote: > > > On Sunday, June 22, 2014 12:45:42 PM Alan Stern wrote: > > > On Sun, 22 Jun 2014, Rafael J. Wysocki wrote: > > > > > > > > How would you treat them specially? Add a "runtime_pm_not_supported" > > > > > flag? > > > > > > > > I thought about a "runtime PM has been enabled at least once" flag > > > > rather > > > > that would be set by pm_runtime_enable() every time it is called and > > > > never > > > > cleared. That would allow the core to distinguish between "runtime PM > > > > disabled temporarily" and "runtime PM not used" which turn out to be > > > > sufficiently different cases. > > > > > > Interesting idea, but it can't tell the difference between "runtime PM > > > not supported" and "runtime PM not enabled yet". I think a simple "not > > > supported" flag will be more straightforward. > > > > The question is who will set the "unsupported" flag (think devices without > > drivers etc.). Or perhaps the idea is that it will be set to start with? > > Drivers or subsystems will set the flag. It should not be set for > devices without drivers or subsystems, because the flag means that the > hardware doesn't support runtime power management, and the kernel > wouldn't know this if there was no driver or subsystem. > > The flag will not be set to start with. The idea is that you set it > when you know for certain that the device cannot be power-managed, but > you still want the Runtime PM API to work with the device. In > particular, calls to pm_runtime_resume() will succeed. > > > > > Yes. The core definitely needs to be able to distinguish between the > > > > "runtime PM disabled temporarily" and "runtime PM not supported/not > > > > used" > > > > situations. > > > > > > Let me work out a patch, and we'll see what you think. For the time > > > being we can stick with our "runtime PM must be disabled (or in error) > > > when the status is changed" approach. > > > > OK > > The patch is below. I haven't tested it with anything meaningful, but > it seems straightforward enough. > > One side point: The patch changes the string displayed for the > power/runtime_status attribute file when disable_depth > 0. Instead of > "unsupported", it will now say "disabled". The attribute will contain > "not supported" when the new flag is set. > > Is this acceptable?
Why change the "unsupported" string? Can't we just leave that one alone? I'd prefer to not break userspace tools... thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
