On Tue, Oct 28, 2014 at 09:58:53PM +0100, Heiko Stübner wrote: > Am Dienstag, 28. Oktober 2014, 10:11:06 schrieb Guenter Roeck: > > 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 <gno...@lxorguk.ukuu.org.uk> > > Cc: Alexander Graf <ag...@suse.de> > > Cc: Andrew Morton <a...@linux-foundation.org> > > Cc: Geert Uytterhoeven <ge...@linux-m68k.org> > > cc: Heiko Stuebner <he...@sntech.de> > > Cc: Lee Jones <lee.jo...@linaro.org> > > Cc: Len Brown <len.br...@intel.com> > > Cc: Pavel Machek <pa...@ucw.cz> > > Cc: Philippe Rétornaz <philippe.retor...@gmail.com> > > Cc: Rafael J. Wysocki <r...@rjwysocki.net> > > Cc: Romain Perier <romain.per...@gmail.com> > > Signed-off-by: Guenter Roeck <li...@roeck-us.net> > > --- > > Similarly to the restart handlers, I really like the concept. > > Acked-by: Heiko Stuebner <he...@sntech.de> >
Thanks! Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
