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kernel/reboot: Introduce sys-off handler API

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In order to support power-off chaining we need to get rid of the global
pm_* variables, replacing them with the new kernel API functions that
support chaining.

Introduce new generic sys-off handler API that brings the following
features:

1. Power-off and restart handlers are registered using same API function
   that supports chaining, hence all power-off and restart modes will
   support chaining using this unified function.

2. Prevents notifier priority collisions by disallowing registration of
   multiple handlers at the non-default priority level.

3. Supports passing opaque user argument to callback, which allows us to
   remove global variables from drivers.

This patch adds support of the following sys-off modes:

- SYS_OFF_MODE_POWER_OFF_PREPARE that replaces global pm_power_off_prepare
  variable and provides chaining support for power-off-prepare handlers.

- SYS_OFF_MODE_POWER_OFF that replaces global pm_power_off variable and
  provides chaining support for power-off handlers.

- SYS_OFF_MODE_RESTART that provides a better restart API, removing a need
  from drivers to have a global scratch variable by utilizing the opaque
  callback argument.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Dmitry Osipenko 2022-05-10 02:32:11 +03:00 committed by Rafael J. Wysocki
parent c82f898d87
commit 232edc2f72
2 changed files with 259 additions and 0 deletions
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77
include/linux/reboot.h
View File

@ -7,6 +7,7 @@
#include <uapi/linux/reboot.h>
struct device;
struct sys_off_handler;
#define SYS_DOWN 0x0001 /* Notify of system down */
#define SYS_RESTART SYS_DOWN
@ -62,6 +63,82 @@ extern void machine_shutdown(void);
struct pt_regs;
extern void machine_crash_shutdown(struct pt_regs *);
/*
* sys-off handler API.
*/
/*
* Standard sys-off priority levels. Users are expected to set priorities
* relative to the standard levels.
*
* SYS_OFF_PRIO_PLATFORM: Use this for platform-level handlers.
*
* SYS_OFF_PRIO_LOW: Use this for handler of last resort.
*
* SYS_OFF_PRIO_DEFAULT: Use this for normal handlers.
*
* SYS_OFF_PRIO_HIGH: Use this for higher priority handlers.
*
* SYS_OFF_PRIO_FIRMWARE: Use this if handler uses firmware call.
*/
#define SYS_OFF_PRIO_PLATFORM -256
#define SYS_OFF_PRIO_LOW -128
#define SYS_OFF_PRIO_DEFAULT 0
#define SYS_OFF_PRIO_HIGH 192
#define SYS_OFF_PRIO_FIRMWARE 224
enum sys_off_mode {
/**
* @SYS_OFF_MODE_POWER_OFF_PREPARE:
*
* Handlers prepare system to be powered off. Handlers are
* allowed to sleep.
*/
SYS_OFF_MODE_POWER_OFF_PREPARE,
/**
* @SYS_OFF_MODE_POWER_OFF:
*
* Handlers power-off system. Handlers are disallowed to sleep.
*/
SYS_OFF_MODE_POWER_OFF,
/**
* @SYS_OFF_MODE_RESTART:
*
* Handlers restart system. Handlers are disallowed to sleep.
*/
SYS_OFF_MODE_RESTART,
};
/**
* struct sys_off_data - sys-off callback argument
*
* @mode: Mode ID. Currently used only by the sys-off restart mode,
* see enum reboot_mode for the available modes.
* @cb_data: User's callback data.
* @cmd: Command string. Currently used only by the sys-off restart mode,
* NULL otherwise.
*/
struct sys_off_data {
int mode;
void *cb_data;
const char *cmd;
};
struct sys_off_handler *
register_sys_off_handler(enum sys_off_mode mode,
int priority,
int (*callback)(struct sys_off_data *data),
void *cb_data);
void unregister_sys_off_handler(struct sys_off_handler *handler);
int devm_register_sys_off_handler(struct device *dev,
enum sys_off_mode mode,
int priority,
int (*callback)(struct sys_off_data *data),
void *cb_data);
/*
* Architecture independent implemenations of sys_reboot commands.
*/

182
kernel/reboot.c
View File

@ -48,6 +48,15 @@ int reboot_cpu;
enum reboot_type reboot_type = BOOT_ACPI;
int reboot_force;
struct sys_off_handler {
struct notifier_block nb;
int (*sys_off_cb)(struct sys_off_data *data);
void *cb_data;
enum sys_off_mode mode;
bool blocking;
void *list;
};
/*
* If set, this is used for preparing the system to power off.
*/
@ -281,6 +290,179 @@ void kernel_halt(void)
}
EXPORT_SYMBOL_GPL(kernel_halt);
/*
* Notifier list for kernel code which wants to be called
* to prepare system for power off.
*/
static BLOCKING_NOTIFIER_HEAD(power_off_prep_handler_list);
/*
* Notifier list for kernel code which wants to be called
* to power off system.
*/
static ATOMIC_NOTIFIER_HEAD(power_off_handler_list);
static int sys_off_notify(struct notifier_block *nb,
unsigned long mode, void *cmd)
{
struct sys_off_handler *handler;
struct sys_off_data data = {};
handler = container_of(nb, struct sys_off_handler, nb);
data.cb_data = handler->cb_data;
data.mode = mode;
data.cmd = cmd;
return handler->sys_off_cb(&data);
}
/**
* register_sys_off_handler - Register sys-off handler
* @mode: Sys-off mode
* @priority: Handler priority
* @callback: Callback function
* @cb_data: Callback argument
*
* Registers system power-off or restart handler that will be invoked
* at the step corresponding to the given sys-off mode. Handler's callback
* should return NOTIFY_DONE to permit execution of the next handler in
* the call chain or NOTIFY_STOP to break the chain (in error case for
* example).
*
* Multiple handlers can be registered at the default priority level.
*
* Only one handler can be registered at the non-default priority level,
* otherwise ERR_PTR(-EBUSY) is returned.
*
* Returns a new instance of struct sys_off_handler on success, or
* an ERR_PTR()-encoded error code otherwise.
*/
struct sys_off_handler *
register_sys_off_handler(enum sys_off_mode mode,
int priority,
int (*callback)(struct sys_off_data *data),
void *cb_data)
{
struct sys_off_handler *handler;
int err;
handler = kzalloc(sizeof(*handler), GFP_KERNEL);
if (!handler)
return ERR_PTR(-ENOMEM);
switch (mode) {
case SYS_OFF_MODE_POWER_OFF_PREPARE:
handler->list = &power_off_prep_handler_list;
handler->blocking = true;
break;
case SYS_OFF_MODE_POWER_OFF:
handler->list = &power_off_handler_list;
break;
case SYS_OFF_MODE_RESTART:
handler->list = &restart_handler_list;
break;
default:
kfree(handler);
return ERR_PTR(-EINVAL);
}
handler->nb.notifier_call = sys_off_notify;
handler->nb.priority = priority;
handler->sys_off_cb = callback;
handler->cb_data = cb_data;
handler->mode = mode;
if (handler->blocking) {
if (priority == SYS_OFF_PRIO_DEFAULT)
err = blocking_notifier_chain_register(handler->list,
&handler->nb);
else
err = blocking_notifier_chain_register_unique_prio(handler->list,
&handler->nb);
} else {
if (priority == SYS_OFF_PRIO_DEFAULT)
err = atomic_notifier_chain_register(handler->list,
&handler->nb);
else
err = atomic_notifier_chain_register_unique_prio(handler->list,
&handler->nb);
}
if (err) {
kfree(handler);
return ERR_PTR(err);
}
return handler;
}
EXPORT_SYMBOL_GPL(register_sys_off_handler);
/**
* unregister_sys_off_handler - Unregister sys-off handler
* @handler: Sys-off handler
*
* Unregisters given sys-off handler.
*/
void unregister_sys_off_handler(struct sys_off_handler *handler)
{
int err;
if (!handler)
return;
if (handler->blocking)
err = blocking_notifier_chain_unregister(handler->list,
&handler->nb);
else
err = atomic_notifier_chain_unregister(handler->list,
&handler->nb);
/* sanity check, shall never happen */
WARN_ON(err);
kfree(handler);
}
EXPORT_SYMBOL_GPL(unregister_sys_off_handler);
static void devm_unregister_sys_off_handler(void *data)
{
struct sys_off_handler *handler = data;
unregister_sys_off_handler(handler);
}
/**
* devm_register_sys_off_handler - Register sys-off handler
* @dev: Device that registers handler
* @mode: Sys-off mode
* @priority: Handler priority
* @callback: Callback function
* @cb_data: Callback argument
*
* Registers resource-managed sys-off handler.
*
* Returns zero on success, or error code on failure.
*/
int devm_register_sys_off_handler(struct device *dev,
enum sys_off_mode mode,
int priority,
int (*callback)(struct sys_off_data *data),
void *cb_data)
{
struct sys_off_handler *handler;
handler = register_sys_off_handler(mode, priority, callback, cb_data);
if (IS_ERR(handler))
return PTR_ERR(handler);
return devm_add_action_or_reset(dev, devm_unregister_sys_off_handler,
handler);
}
EXPORT_SYMBOL_GPL(devm_register_sys_off_handler);
/**
* kernel_power_off - power_off the system
*