AsiaBSDCon DEVSUMMIT patch

[M. Warner Losh]

In message: <20080326230322.H72156 at desktop>
            Jeff Roberson <jroberson at chesapeake.net> writes:
: 
: On Thu, 27 Mar 2008, M. Warner Losh wrote:
: 
: > Greetings,
: >
: > We've been talking about the situation with suspend/resume in the
: > tree.  Here's a quick hack to allow one to suspend/resume an
: > individual device.  This may or may not work too well, but it is
: > offered up for testing and criticism.
: >
: > 	http://people.freebsd.org/~imp/devctl.diff
: >
: > devctl -s ath 0		suspend ath0
: > devctl -r ath 0		resume ath0
: 
: Hey Warner,
: 
: This is a great idea.  Would it be possible to provide a little more 
: background about what the expected failure/success modes are?  If we had 
: some easy to follow steps we could ask for testers on current@ and create 
: a wiki with a list of known working/broken hardware.  That'd be a great 
: step towards having widespread suspend/resume support.

There's two areas of testing/use here.

The first is to run it like so:

devctl -s ath 0 && sleep 10 && devctl -r ath 0

Eg, suspend and resume an individual device, or even tree of devices.
At least one bug has been found with this technique (it is actually a
rediscovery of an older bug, but I digress).  You'd want the kernel to
not panic, and you'd want things to be good after as before.

One can also use it to test to make sure that a device remains sane
after a long time suspended as well.  This can have power savings
potential too, but that's a secondary effect at this time.

Warner