Re: [PATCH v2 08/45] kernel: Add combined power-off+restart handler call chain API

[Dmitry Osipenko <digetx@gmail.com>]

28.10.2021 12:59, Rafael J. Wysocki пишет:
>> +#define RESTART_PRIO_RESERVED          0
>> +#define RESTART_PRIO_DEFAULT           128
>> +#define RESTART_PRIO_HIGH              192
>>
>>  enum reboot_mode {
>>         REBOOT_UNDEFINED = -1,
>> @@ -49,6 +55,167 @@ int register_restart_handler(struct notifier_block *);
>>  int unregister_restart_handler(struct notifier_block *);
>>  void do_kernel_restart(char *cmd);
>>
>> +/*
>> + * Unified poweroff + restart API.
>> + */
>> +
>> +#define POWEROFF_PRIO_RESERVED         0
>> +#define POWEROFF_PRIO_PLATFORM         1
>> +#define POWEROFF_PRIO_DEFAULT          128
>> +#define POWEROFF_PRIO_HIGH             192
>> +#define POWEROFF_PRIO_FIRMWARE         224
> Also I'm wondering why these particular numbers were chosen, here and above?

These values are chosen based on priorities that drivers already use. I looked thorough them all and ended with this scheme that fulfills the needs of the current API users.

I'll add these comments in v3:

/*
 * Standard restart priority levels. Intended to be set in the
 * sys_off_handler.restart_priority field.
 *
 * Use `RESTART_PRIO_XXX +- prio` style for additional levels.
 *
 * RESTART_PRIO_RESERVED:	Falls back to RESTART_PRIO_DEFAULT.
 *				Drivers may leave priority initialized
 *				to zero, to auto-set it to the default level.
 *
 * RESTART_PRIO_DEFAULT:	Use this for generic handler.
 *
 * RESTART_PRIO_HIGH:		Use this if you have multiple handlers and
 *				this handler has higher priority than the
 *				default handler.
 */

/*
 * Standard power-off priority levels. Intended to be set in the
 * sys_off_handler.power_off_priority field.
 *
 * Use `POWEROFF_PRIO_XXX +- prio` style for additional levels.
 *
 * POWEROFF_PRIO_RESERVED:	Falls back to POWEROFF_PRIO_DEFAULT.
 *				Drivers may leave priority initialized
 *				to zero, to auto-set it to the default level.
 *
 * POWEROFF_PRIO_PLATFORM:	Intended to be used by platform-level handler.
 *				Has lowest priority since device drivers are
 *				expected to take over platform handler which
 *				doesn't allow further callback chaining.
 *
 * POWEROFF_PRIO_DEFAULT:	Use this for generic handler.
 *
 * POWEROFF_PRIO_HIGH:		Use this if you have multiple handlers and
 *				this handler has higher priority than the
 *				default handler.
 *
 * POWEROFF_PRIO_FIRMWARE:	Use this if handler uses firmware call.
 *				Has highest priority since firmware is expected
 *				to know best how to power-off hardware properly.
 */