Re: [PATCH 1/3] scsi: pm: add may_power_off flag

[Aaron Lu <aaron.lwe@gmail.com>]

On Thu, Aug 30, 2012 at 10:24:39AM -0400, Alan Stern wrote:
> On Thu, 30 Aug 2012, Aaron Lu wrote:
> 
> > Add a new flag may_power_off for scsi device, it gives the user a chance
> > to control when the device is runtime suspended, can we remove its power
> > if possible.
> > 
> > I'm planning using this flag for sr and sd.
> > 
> > For sr, if user set 0 to may_power_off, we will disable runtime suspend
> > for ODD, since runtime suspend for ODD is wholly for zero power ODD, if
> > we can't power off the ODD, there is no meaning to do runtime PM on it.
> 
> This doesn't seem like a good idea.  Even though you may not be able to
> reduce the drive's power usage, you can still allow the runtime_suspend
> routine to succeed.  This will tell the kernel to consider the drive as
> being in a suspended (and therefore unusable) state, allowing the
> kernel to do a runtime suspend of the SCSI host that the drive is
> attached to.

Thanks Alan, I agree that this doesn't quite follow the meaning of
may_power_off.

I tried to seperate runtime pm with runtime power off in v5 patch of
ZPODD, please take a look to see if I did it the right way.

Thanks,
Aaron