linux-kernel - Re: [PATCH v7 3/4] block: implement runtime pm strategy

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Date:	Sat, 19 Jan 2013 13:11:45 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Aaron Lu <aaron.lu@...el.com>
cc:	Jens Axboe <axboe@...nel.dk>, "Rafael J. Wysocki" <rjw@...k.pl>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	<linux-pm@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Aaron Lu <aaron.lwe@...il.com>,
	Shane Huang <shane.huang@....com>
Subject: Re: [PATCH v7 3/4] block: implement runtime pm strategy

On Sat, 19 Jan 2013, Aaron Lu wrote:

> > Okay.  I think you can add (in parentheses) that in most cases drivers
> > should call the routine before any I/O has taken place.
> 
> The reason I put it that way is, in patch 4, the blk_pm_runtime_init is
> called after a request is executed(scsi_probe_lun). I do not want people
> get confused by the comments for blk_pm_runtime_init and the example
> code in patch 4 where we didn't follow it :-)

Right.

> Considering ODD's use case, I was thinking of moving the
> blk_pm_runtime_init call to sd.c, as sr will not use request based auto
> suspend. Probably right before we decrease usage count for the device in
> sd_probe_async. What do you think?

That makes sense.  But then you should review the changes in scsi_pm.c 
to make sure they will work okay for devices that aren't using 
block-layer runtime PM.

Alan Stern

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