#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#define IOCTL_BACKLIGHT 0x83102144
#define BACKLIGHT_CAPABILITY 0x01
#define BACKLIGHT_STATUS 0x32
#define BACKLIGHT_OFF 0x00033
#define BACKLIGHT_LEVEL1 0x10033
#define BACKLIGHT_LEVEL2 0x20033
#define BACKLIGHT_AUTO 0x30033
char *get_base_name(char *path)
{
if (!path) {
return NULL;
}
char *an = NULL;
char *p = path;
while (*p++) {
if (*p == '\\' || *p == '/') {
an = p;
}
}
return (an == NULL) ? path : (an + 1);
}
uint32_t device_io_control(HANDLE drv_handle, uint32_t func)
{
char outbuff[4] = { 0 };
DWORD ret_len = 0;
if (DeviceIoControl(drv_handle, IOCTL_BACKLIGHT, &func, sizeof(func), outbuff, sizeof(outbuff), &ret_len, NULL)) {
outbuff[ret_len] = '\0';
return (outbuff[3] << 24) | (outbuff[2] << 16) | (outbuff[1] << 8) | outbuff[0];
} else {
fprintf(stderr, "Error: DeviceIoControl failed, func=%d\n", func);
return (uint32_t) -1;
}
}
uint32_t get_backlight_capability(HANDLE drv_handle)
{
return device_io_control(drv_handle, BACKLIGHT_CAPABILITY);
}
uint32_t get_backlight_status(HANDLE drv_handle)
{
return device_io_control(drv_handle, BACKLIGHT_STATUS);
}
uint32_t set_backlight_level(HANDLE drv_handle, int level)
{
uint32_t func = BACKLIGHT_AUTO;
switch (level) {
case 0:
func = BACKLIGHT_OFF;
break;
case 1:
func = BACKLIGHT_LEVEL1;
break;
case 2:
func = BACKLIGHT_LEVEL2;
break;
}
return device_io_control(drv_handle, func);
}
int main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, "Usage: %s [0|1|2|3]\n", get_base_name(argv[0]));
return -1;
}
int level = (int) strtol(argv[1], NULL, 0);
if (level < 0 || level > 3) {
fprintf(stderr, "Usage: %s [0|1|2|3]\n", get_base_name(argv[0]));
return -1;
}
/* open */
HANDLE drv_handle = CreateFileA("\\\\.\\EnergyDrv", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (drv_handle == INVALID_HANDLE_VALUE) {
fprintf(stderr, "Error: Failed to find device, make sure Lenovo energy management driver is installed!\n");
return -1;
}
/* run */
do {
/* cap */
uint32_t cap = get_backlight_capability(drv_handle);
if (cap == (uint32_t) -1) {
break;
}
if ((cap & 1) != 1) {
fprintf(stderr, "Error: Failed to get capability!\n");
break;
}
if ((cap >> 1) != 3) {
fprintf(stderr, "Error: Auto-level not supported!\n");
break;
}
/* status */
uint32_t status = get_backlight_status(drv_handle);
if (status == (uint32_t) -1) {
break;
}
if ((status & 1) != 1) {
fprintf(stderr, "Error: Failed to get current status!\n");
break;
}
status = status >> 1;
if ((status & 0x8000) != 0x8000) {
fprintf(stderr, "Error: Cannot set backlight when keyboard is disabled!\n");
break;
}
int curr_level = -1;
switch (status & 0x7fff) {
case 0:
curr_level = 0;
break;
case 1:
curr_level = 1;
break;
case 2:
curr_level = 2;
break;
case 3:
curr_level = 3;
break;
}
printf("Current level: %d\n", curr_level);
set_backlight_level(drv_handle, level);
printf("Finished setting level: %d\n", level);
} while (FALSE);
/* close */
CloseHandle(drv_handle);
return 0;
}
. See code: