Re: [PATCH v6 1/7] scsi: sr: support runtime pm for ODD

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On Thu, 6 Sep 2012, Oliver Neukum wrote:

> On Thursday 06 September 2012 11:06:49 Alan Stern wrote:
> > On Thu, 6 Sep 2012, Aaron Lu wrote:
> > 
> > > > That's why we have an autosuspend delay.  Although for some reason the 
> > > > SCSI subsystem doesn't use it currently...  We need to add a call to 
> > > > pm_runtime_use_autosuspend() in scsi_sysfs_add_sdev().  Likewise, the 
> > > > pm_schedule_suspend() call in scsi_runtime_idle() should be changed to 
> > > > pm_runtime_autosuspend().  And there should be calls to 
> > > > pm_runtime_set_autosuspend_delay() in the sd and sr drivers.
> > > 
> > > I tried to use autosuspend when preparing the patch, but the fact that
> > > the devices will be polled every 2 seconds make it impossible to enter
> > > suspend state if the autosuspend delay is larger than that.
> > 
> > You can always increase the polling interval.
> > 
> > But in the long run that wouldn't be a good solution.  What I'd really 
> > like is a way to do the status polling without having it reset the 
> > idle timer.
> > 
> > Oliver, what do you think?  Would that be a good solution?
> 
> Well, we could introduce a flag into the requests for the polls.
> But best would be to simply declare a device immediately idle
> as soon as we learn that it has no medium. No special casing
> would be needed.

We could do that, but what about idle drives that do have media?

Alan Stern

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