On Fri, Nov 26, 2021 at 09:00:44PM +0300, Dmitry Osipenko wrote:
SoC platforms often have multiple ways of how to perform system's power-off and restart operations. Meanwhile today's kernel is limited to a single option. Add combined power-off+restart handler call chain API, which is inspired by the restart API. The new API provides both power-off and restart functionality. The old pm_power_off method will be kept around till all users are converted to the new API. Current restart API will be replaced by the new unified API since new API is its superset. The restart functionality of the sys-off handler API is built upon the existing restart-notifier APIs. In order to ease conversion to the new API, convenient helpers are added for the common use-cases. They will reduce amount of boilerplate code and remove global variables. These helpers preserve old behaviour for cases where only one power-off handler is expected, this is what all existing drivers want, and thus, they could be easily converted to the new API. Users of the new API should explicitly enable power-off chaining by setting corresponding flag of the power_handler structure.
[...] Hi, A general question: do we really need three distinct chains for this? Can't there be only one that chain of callbacks that get a stage (RESTART_PREPARE, RESTART, POWER_OFF_PREPARE, POWER_OFF) and can ignore them at will? Calling through POWER_OFF_PREPARE would also return whether that POWER_OFF is possible (for kernel_can_power_off()). I would also split this patch into preparation cleanups (like wrapping pm_power_off call with a function) and adding the notifier-based implementation. Best Regards Michał Mirosław
