linux-kernel - Re: [PATCH v7 4/4] sd: change to auto suspend mode

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Message-ID: <Pine.LNX.4.44L0.1301281011570.1997-100000@iolanthe.rowland.org>
Date:	Mon, 28 Jan 2013 10:12:44 -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 4/4] sd: change to auto suspend mode

On Mon, 28 Jan 2013, Aaron Lu wrote:

> > Someone just asked about the default autosuspend delay, and I realized
> > your patch series doesn't set one.  Since we don't know the properties
> > of the disk drive at this point (or even whether the device is a disk
> > drive), the only safe course is to call
> > 
> > 	pm_runtime_set_autosuspend_delay(&sdev->sdev_gendev, -1);
> > 
> > before calling blk_pm_runtime_init().  Then autosuspends will be 
> > prevented until userspace writes a non-negative value into the device's 
> > control/autosuspend_delay_ms file.
> 
> Shall we do it inside blk_pm_runtime_init? This way, we do not need to
> do it for every driver. And for drivers that do know a proper value for
> autosuspend delay, they can call pm_runtime_set_autosuspend_delay
> somewhere after blk_pm_runtime_init.

Yes, that seems like a good approach.  Be sure to mention it in the 
kerneldoc.

Alan Stern

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