#include <zircon/syscalls.h>

zx_status_t zx_system_powerctl(zx_handle_t resource,
                               uint32_t cmd,
                               const zx_system_powerctl_arg_t* arg);


zx_system_powerctl changes the power state of the system based on the value of cmd. Zircon may not be able to put the system in a given power state, depending on its level of support for the architecture being used.

arg is an optional pointer to a struct which provides further information about the command to be executed.



Sets all processor cores as active.

arg type: n/a


Set only the primary CPU as active.

arg type: n/a


Only defined for x86-64.

Currently only transitions to the S3 state are supported.

Before calling this syscall the following steps should be taken: 1. Enter ACPICA noncontested mode 2. Shut down the secondary CPUs 3. Execute the _PTS control method 4. (Optional) Execute the _SST control method 5. Clear the ACPI wake status bit register 6. Disable all ACPI GPEs 7. Enabled all ACPI wakeup GPEs

arg type: zx_system_powerctl_arg_t with only the acpi_transition_s_state union element considered valid.

struct {
    uint8_t target_s_state;  // Value between 1 and 5 indicating which S-state
    uint8_t sleep_type_a;    // Value from ACPI VM (SLP_TYPa)
    uint8_t sleep_type_b;    // Value from ACPI VM (SLP_TYPb)
} acpi_transition_s_state;

Returns ZX_ERR_INVALID_ARGS if the target S state is not in the range 1-5.

Returns ZX_ERR_NOT_SUPPORTED if transitioning to the target S state is not supported.

Returns ZX_ERR_BAD_STATE if the target S state is not 5 and the secondary CPUs have not been shut down.

Returns ZX_ERR_NO_MEMORY if there are not enough resources to run the thread.

Returns ZX_ERR_INTERNAL if the S state transition fails.


Only defined for x86-64.

Set CPU to power level 1.

arg type: zx_system_powerctl_arg_t with only the x86_power_limit union element considered valid.

struct {
    uint32_t power_limit;  // PL1 value in milliwatts
    uint32_t time_window;  // PL1 time window in microseconds
    uint8_t clamp;         // PL1 clamping enable
    uint8_t enable;        // PL1 enable
    uint8_t padding2[2];
} x86_power_limit;


Restart the system, control should go through any relevant firmware and bootloaders.

arg type: n/a


Restart the system, but stop in the bootloader instead of loading the operating system.

arg type: n/a


Restart the system, but load the recovery operating system instead of the primary OS.

arg type: n/a


Turn the system off.

arg type: n/a


Used by userspace when it is ready for a reboot in response to a previous signal from the kernel that the kernel wanted to reboot the system.

arg type: n/a

Returns ZX_ERR_BAD_STATE if the kernel has not previously signaled a desire to reboot.


resource must have resource kind ZX_RSRC_KIND_SYSTEM with base ZX_RSRC_SYSTEM_POWER_BASE.

Return value



Returns ZX_ERR_INVALID_ARGS when an unrecognized cmd value is supplied.

See also