Re: [PATCH v12 7/9] libata: scsi: no poll when ODD is powered off

[Aaron Lu <aaron.lu@intel.com>]

On Thu, Jan 10, 2013 at 11:56:10AM -0800, Tejun Heo wrote:
> On Thu, Jan 10, 2013 at 05:24:28PM +0800, Aaron Lu wrote:
> > @@ -182,6 +182,13 @@ void zpodd_enable_run_wake(struct ata_device *dev)
> >  {
> >  	struct zpodd *zpodd = dev->zpodd;
> >  
> > +	/*
> > +	 * Silence the media change poll, as we will be notified when
> > +	 * user wants to use the ODD so there is no meaning to poll
> > +	 * it when it is powered off
> > +	 */
> > +	dev->sdev->disable_disk_events = true;
> 
> What's the synchronization rule for this field?

I documented the rule in include/scsi/scsi_device.h.

This field is modified in the ata port's runtime suspend and resume
callback, and is read accessed in the check_events callback of the sr
block driver. The runtime PM callback is synchronized by PM core, in
that the two callbacks will never run concurrently. So I guess saying
synchronized by PM core is enough for this field?

This is what I've added in v12 for scsi_device structure:

+	bool disable_disk_events; /* disable poll for disk events, used in
+				   * ATA layer, sychronized by PM core */
+

Or do you mean I should add a comment explaining the sync rule when it
is modifed, like in the above code?

Thanks,
Aaron

> 
> Thanks.
> 
> -- 
> tejun