Hi Thierry, > > > [...] > > > > Please use register_restart_handler() instead. It has support for > > priorities, is not arm specific and properly supports unregistering > > (some handler with lower priority will take over). You can check > > gpio-restart as an example for the API. > > > > If you have some other arm_pm_restart handler (those are tried first) > > I suggest to convert that to the restart handler framework. Actually > > it may be a good idea to convert all of them and drop arm_pm_restart, > > since there are only 4 left: > > > > $ git grep "arm_pm_restart =" > > drivers/firmware/psci.c: arm_pm_restart = psci_sys_reset; > > arch/arm/mach-prima2/rstc.c: arm_pm_restart = sirfsoc_restart; > > arch/arm/xen/enlighten.c: arm_pm_restart = xen_restart; > > arch/arm/kernel/setup.c: arm_pm_restart = mdesc->restart; > > > > The first 3 should be easy to update and the last one could > > be solved by registering a wrapper function as restart handler, > > which calls mdesc->restart(). > > I remember this not being the first time that this confuses me. And from > looking around a little it seems like I'm not the only one. > > Do you know if there's ever been any attempts to formalize all of this > by adding some sort of framework for this? That way some of the > confusion may be removed and architecture-specific bits could be > eliminated more easily.
We have a framework for restart handlers, which has been written
by Guenter Roeck [0] in 2014. You just have to call register_restart_handler()
during probe and unregister_restart_handler() during removal of
your reboot driver. All reboot drivers in drivers/power/reset use
that framework.
The restart handlers are invoked by calling do_kernel_restart()
based on their configured priority. That function is called by
the architecture's machine_restart() function. It's currently
used by mips, ppc, arm & arm64 as far as I can see. ARM's
implementation looks like this:
if (arm_pm_restart)
arm_pm_restart()
else
do_kernel_restart() /* reboot handler framework */
No such thing exists for poweroff. Guenter also wrote something for
that [1], but Linus intervened [2]. Anyways, pm_power_off is at
least architecture independent.
[0] https://lwn.net/Articles/605298/
[1] https://lwn.net/Articles/617345/
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-June/351369.html
-- Sebastian
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