main/syscalls/system_powerctl.md

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# zx_system_powerctl

## Summary

TODO(https://fxbug.dev/42108078)

## Declaration

```c
#include <zircon/syscalls.h>

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

## Description

`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.

## COMMANDS

### ZX_SYSTEM_POWERCTL_ENABLE_ALL_CPUS

Sets all processor cores as active.

*arg* type: `n/a`

### ZX_SYSTEM_POWERCTL_DISABLE_ALL_CPUS_BUT_PRIMARY

Set only the primary CPU as active.

*arg* type: `n/a`

### ZX_SYSTEM_POWERCTL_ACPI_TRANSITION_S_STATE

Only defined for x86-64, but is no longer supported.

Returns `ZX_ERR_NOT_SUPPORTED`.

### ZX_SYSTEM_POWERCTL_X86_SET_PKG_PL1

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.

```c
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;
```

### ZX_SYSTEM_POWERCTL_REBOOT

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

*arg* type: `n/a`

### ZX_SYSTEM_POWERCTL_REBOOT_BOOTLOADER

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

*arg* type: `n/a`

### ZX_SYSTEM_POWERCTL_REBOOT_RECOVERY

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

*arg* type: `n/a`

### ZX_SYSTEM_POWERCTL_SHUTDOWN

Turn the system off.

*arg* type: `n/a`

### ZX_SYSTEM_POWERCTL_ACK_KERNEL_INITIATED_REBOOT

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.

## Rights

*resource* must have resource kind `ZX_RSRC_KIND_SYSTEM` with base `ZX_RSRC_SYSTEM_POWER_BASE`.

## Return value

`ZX_OK`

## Errors

Returns `ZX_ERR_INVALID_ARGS` when an unrecognized `cmd` value is supplied.

## See also

TODO(https://fxbug.dev/42108078)