Re: + rework-pm_ops-pm_disk_mode-kill-misuse.patch added to -mm tree

Johannes Berg
2007-03-22T17:51:18Z

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On Thu, 2007-03-22 at 09:36 -0800, Andrew Morton wrote:

> Johannes, this patch series has caused a lot of confusion.

Yeah, I didn't intend to cause that much confusion. Sorry about that.

> Perhaps you
> could generate an additional couple of overview paragraphs for the changelog
> which address the points of confusion, and which prevent the next set of
> reviewers from hitting the same things?

Sure. Most of this is in the pm_ops kerneldoc now. How's this?

This patch series cleans up some misconceptions about pm_ops. Some users
of the pm_ops structure attempt to use it to stop the user from entering
suspend to disk, this, however, is not possible since the user can
always use "shutdown" in /sys/power/disk and then the pm_ops are never
invoked. Also, platforms that don't support suspend to disk simply
should not allow configuring SOFTWARE_SUSPEND (read the help text on it,
it only selects suspend to disk and nothing else, all the other stuff
depends on PM).

The pm_ops structure is actually intended to provide a way to enter
platform-defined sleep states (currently supported states are "standby"
and "mem" (suspend to ram)) and additionally (if SOFTWARE_SUSPEND is
configured) allows a platform to support a platform specific way to
enter low-power mode once everything has been saved to disk. This is
currently only used by ACPI (S4).

johannes

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