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SubjectRe: [PATCH 1/3] PM / Sleep: Mark devices involved in wakeup signaling during suspend
Hi Rafael

Just something, that made me wonder:

On Thu, 20 Oct 2011, Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <>
> The generic PM domains code in drivers/base/power/domain.c has
> to avoid powering off domains that provide power to wakeup devices
> during system suspend. Currently, however, this only works for
> wakeup devices directly belonging to the given domain and not for
> their children (or the children of their children and so on).
> Thus, if there's a wakeup device whose parent belongs to a power
> domain handled by the generic PM domains code, the domain will be
> powered off during system suspend preventing the device from
> signaling wakeup.
> To address this problem introduce a device flag, power.wakeup_path,
> that will be set during system suspend for all wakeup devices,
> their parents, the parents of their parents and so on. This way,
> all wakeup paths in the device hierarchy will be marked and the
> generic PM domains code will only need to avoid powering off
> domains containing devices whose power.wakeup_path is set.
> Signed-off-by: Rafael J. Wysocki <>
> ---
> drivers/base/power/domain.c | 4 ++--
> drivers/base/power/main.c | 8 +++++++-
> include/linux/pm.h | 1 +
> 3 files changed, 10 insertions(+), 3 deletions(-)


> Index: linux/include/linux/pm.h
> ===================================================================
> --- linux.orig/include/linux/pm.h
> +++ linux/include/linux/pm.h
> @@ -452,6 +452,7 @@ struct dev_pm_info {
> struct list_head entry;
> struct completion completion;
> struct wakeup_source *wakeup;
> + bool wakeup_path:1;

This is an interesting idea... I'd presume, the compiler is aware, that
one bit is enough for "bool," so, it should choose an optimal
implementation by itself? I checked gcc 4.4.1 on ARM - without the
bitfield notation the compiler just uses one byte in my example. Anyway,
not a request-for-change, just wondering whether you really were trying to
(potentially) save a couple of bits here or what was the motivation.

> #else
> unsigned int should_wakeup:1;
> #endif

Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer

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