Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v5 01/48] kernel: Add support for power-off handler call chain | Date | Thu, 06 Nov 2014 23:30:59 +0100 |
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On Thursday, November 06, 2014 08:42:45 AM 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> > Cc: Pavel Machek <pavel@ucw.cz> > Cc: Philippe Rétornaz <philippe.retornaz@gmail.com> > Cc: Rafael J. Wysocki <rjw@rjwysocki.net> > Cc: Romain Perier <romain.perier@gmail.com> > Acked-by: Pavel Machek <pavel@ucw.cz> > Acked-by: Heiko Stuebner <heiko@sntech.de> > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > --- > v5: > - Rebase to v3.18-rc3 > v4: > - Do not use notifiers but internal functions and data structures to manage > the list of power-off handlers. Drop unused parameters from callbacks, and > make the power-off function type void. > Code to manage and walk the list of callbacks is derived from notifier.c. > v3: > - Rename new file to power_off_handler.c > - Replace poweroff in all newly introduced variables and in text > with power_off or power-off as appropriate > - Replace POWEROFF_PRIORITY_xxx with POWER_OFF_PRIORITY_xxx > - Execute power-off handlers without any locks held > v2: > - poweroff -> power_off > - Add defines for default priorities > - Use raw notifiers protected by spinlocks instead of atomic notifiers > - Add register_poweroff_handler_simple > - Add devm_register_power_off_handler > > include/linux/pm.h | 28 ++++ > kernel/power/Makefile | 1 + > kernel/power/power_off_handler.c | 293 +++++++++++++++++++++++++++++++++++++++ > 3 files changed, 322 insertions(+) > create mode 100644 kernel/power/power_off_handler.c > > diff --git a/include/linux/pm.h b/include/linux/pm.h > index 383fd68..a4d6bf8 100644 > --- a/include/linux/pm.h > +++ b/include/linux/pm.h > @@ -35,6 +35,34 @@ extern void (*pm_power_off)(void); > extern void (*pm_power_off_prepare)(void); > > struct device; /* we have a circular dep with device.h */ > + > +/* > + * Data structures and callbacks to manage power-off handlers > + */ > + > +struct power_off_handler_block { > + void (*handler)(struct power_off_handler_block *); > + struct power_off_handler_block __rcu *next; > + int priority; > +}; > + > +int register_power_off_handler(struct power_off_handler_block *); > +int devm_register_power_off_handler(struct device *, > + struct power_off_handler_block *); > +int register_power_off_handler_simple(void (*function)(void), int priority); > +int unregister_power_off_handler(struct power_off_handler_block *); > +void do_kernel_power_off(void); > +bool have_kernel_power_off(void); > + > +/* > + * Pre-defined power-off handler priorities > + */ > +#define POWER_OFF_PRIORITY_FALLBACK 0 > +#define POWER_OFF_PRIORITY_LOW 64 > +#define POWER_OFF_PRIORITY_DEFAULT 128 > +#define POWER_OFF_PRIORITY_HIGH 192 > +#define POWER_OFF_PRIORITY_HIGHEST 255
I'm not sure why we need these gaps in the priority space.
I guess it might be possible to use
enum power_off_priority { POWER_OFF_PRIORITY_FALLBACK = 0, POWER_OFF_PRIORITY_LOW, POWER_OFF_PRIORITY_DEFAULT, POWER_OFF_PRIORITY_HIGH, POWER_OFF_PRIORITY_HIGHEST, POWER_OFF_PRIORITY_LIMIT, };
and then make register_ complain if priority is POWER_OFF_PRIORITY_LIMIT or greater.
But I'm OK with the rest, so if no one else sees a problem here, I'm not going to make a fuss about it.
Rafael
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