From c48825251cf5950da9d618144c4db6c130e6c0cd Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 13 Feb 2012 16:29:47 +0100 Subject: PM: Add comment describing relationships between PM callbacks to pm.h The UNIVERSAL_DEV_PM_OPS() macro is slightly misleading, because it may suggest that it's a good idea to point runtime PM callback pointers to the same routines as system suspend/resume callbacks .suspend() and .resume(), which is not the case. For this reason, add a comment to include/linux/pm.h, next to the definition of UNIVERSAL_DEV_PM_OPS(), describing how device PM callbacks are related to each other. Signed-off-by: Rafael J. Wysocki --- include/linux/pm.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux/pm.h') diff --git a/include/linux/pm.h b/include/linux/pm.h index 73c610573a7..d6dd6f612b8 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -320,6 +320,15 @@ const struct dev_pm_ops name = { \ /* * Use this for defining a set of PM operations to be used in all situations * (sustem suspend, hibernation or runtime PM). + * NOTE: In general, system suspend callbacks, .suspend() and .resume(), should + * be different from the corresponding runtime PM callbacks, .runtime_suspend(), + * and .runtime_resume(), because .runtime_suspend() always works on an already + * quiescent device, while .suspend() should assume that the device may be doing + * something when it is called (it should ensure that the device will be + * quiescent after it has returned). Therefore it's better to point the "late" + * suspend and "early" resume callback pointers, .suspend_late() and + * .resume_early(), to the same routines as .runtime_suspend() and + * .runtime_resume(), respectively (and analogously for hibernation). */ #define UNIVERSAL_DEV_PM_OPS(name, suspend_fn, resume_fn, idle_fn) \ const struct dev_pm_ops name = { \ -- cgit v1.2.3