Messages in this thread | | | Date | Tue, 28 Oct 2014 19:23:12 +0100 | From | Pavel Machek <> | Subject | Re: [PATCH v4] kernel: Add support for power-off handler call chain |
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On Tue 2014-10-28 10:11:06, Guenter Roeck wrote: > Various drivers implement architecture and/or device specific means to > power off the system. For the most part, those drivers set the global > variable pm_power_off to point to a function within the driver. > > This mechanism has a number of drawbacks. Typically only one scheme > to remove power is supported (at least if pm_power_off is used). > At least in theory there can be multiple means remove power, some of > which may be less desirable. For example, some mechanisms may only > power off the CPU or the CPU card, while another may power off the > entire system. Others may really just execute a restart sequence > or drop into the ROM monitor. Using pm_power_off can also be racy > if the function pointer is set from a driver built as module, as the > driver may be in the process of being unloaded when pm_power_off is > called. If there are multiple power-off handlers in the system, removing > a module with such a handler may inadvertently reset the pointer to > pm_power_off to NULL, leaving the system with no means to remove power. > > Introduce a system power-off handler call chain to solve the described > problems. This call chain is expected to be executed from the architecture > specific machine_power_off() function. Drivers and architeceture code > providing system power-off functionality are expected to register with > this call chain. When registering a power-off handler, callers can > provide a priority to control power-off handler execution sequence > and thus ensure that the power-off handler with the optimal capabilities > to remove power for a given system is called first. > > Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk> > Cc: Alexander Graf <agraf@suse.de> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Geert Uytterhoeven <geert@linux-m68k.org> > cc: Heiko Stuebner <heiko@sntech.de> > Cc: Lee Jones <lee.jones@linaro.org> > Cc: Len Brown <len.brown@intel.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
-- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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