Re: [linux-pm] [GIT PULL] PM updates for 2.6.33

Victor Lowther
2009-12-06T19:04:36Z

On Sun, 2009-12-06 at 10:23 -0500, Alan Stern wrote:
> On Sat, 5 Dec 2009, Linus Torvalds wrote:
> That's ridiculous. Having gone to all the trouble of building a device
> tree, one which is presumably still almost entirely correct, why go to
> all the trouble of tearing it down only to rebuild it again? (Note:
> I'm talking about resume-from-RAM here, not resume-from-hibernation.)

There should be nothing special or privileged at all about the device
tree that gets built at boot time.

Consider the scenario of the laptop user with a docking station.
Adding, removing, and rewriting vast swaths of the device tree across
suspend/resume and hibernate/thaw is very easy to do when you are
plugging a laptop into one or more docking stations.

> Instead what we do is verify that the devices we remember from before
> the suspend are still there, and then asynchronously handle new devices
> which have been plugged in during the meantime. Doing this involves
> relatively little extra or new code; most of the routines are shared
> with the runtime PM and device reset paths.

Devices can vanish across suspend to RAM just as easily as they can be
added.

>
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