On Mon, 16 Jun 2014, Rafael J. Wysocki wrote: > > For reasons having nothing to do with Allen's suggested change, I > > wonder if we shouldn't replace this line with something like: > > > > - else if (dev->power.disable_depth == 1 && dev->power.is_suspended > > + else if (dev->power.disable > 0 && !dev->power.is_suspended > > && dev->power.runtime_status == RPM_ACTIVE) > > retval = 1; > > > > It seems that I've been bitten by this several times in the past. > > When a device is disabled for runtime PM, and more or less permanently > > stuck in the RPM_ACTIVE state, calls to pm_runtime_resume() or > > pm_runtime_get_sync() shouldn't fail. > > > > For example, suppose some devices of a certain type support runtime > > power management but others don't. We naturally want to call > > pm_runtime_disable() for the ones that don't. But we also want the > > same driver to work for all the devices, which means that > > pm_runtime_get_sync() should return success -- otherwise the driver > > will think that something has gone wrong. > > > > Rafael, what do you think? > > That condition is there specifically to take care of the system suspend > code path. It means that if runtime PM is disabled, but it only has been > disabled by the system suspend code path, we should treat the device as > "active" (ie. return 1). That won't work after the proposed change.
Ah, yes, quite true. Okay, suppose we replace that line with just: + else if (dev->power.disable > 0 > I guess drivers that want to work with devices where runtime PM may be > disabled can just check the return value of rpm_resume() for -EACCES? They could, but it's extra work and it's extremely easy to forget about. I'd prefer not to do things that way. Alan Stern -- 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/
