linux-kernel - Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation callbacks (rev. 6)

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Message-Id: <200804021622.04461.oliver@neukum.org>
Date:	Wed, 2 Apr 2008 16:22:03 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Nigel Cunningham <ncunningham@...a.org.au>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg KH <greg@...ah.com>, Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexey Starikovskiy <astarikovskiy@...e.de>,
	David Brownell <david-b@...bell.net>,
	Pavel Machek <pavel@....cz>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation callbacks (rev. 6)

Am Mittwoch, 2. April 2008 16:11:14 schrieb Alan Stern:
> > However, I'd like to add a recommendation that the _new_ "resume" callbacks
> > should only return errors in critical situations as the indication to the PM
> > core that something went _really_ wrong and the device in question is quite
> > surely unusable.
> 
> Agreed.  The most important aspect is that drivers should _not_ return
> an error if the device is working correctly.  We should fix the drivers 
> which make this mistake.

We need to do something about devices that don't want to be resumed.
There's code like this:


static int usb_resume(struct device *dev)
{
	struct usb_device	*udev;

	if (!is_usb_device(dev))	/* Ignore PM for interfaces */
		return 0;
	udev = to_usb_device(dev);

	/* If udev->skip_sys_resume is set then udev was already suspended
	 * when the system suspend started, so we don't want to resume
	 * udev during this system wakeup.  However a reset-resume counts
	 * as a wakeup event, so allow a reset-resume to occur if remote
	 * wakeup is enabled. */
	if (udev->skip_sys_resume) {
		if (!(udev->reset_resume && udev->do_remote_wakeup))
			return -EHOSTUNREACH;
	}
	return usb_external_resume_device(udev);
}

Do we want to keep this in the subsystems?

	Regards
		Oliver
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