10.2. 配置电源管理状态

main()

static int pm_qos_fd = -1;

void start_low_latency(void)
{
	s32_t target = 0;

	if (pm_qos_fd >= 0)
		return;
	pm_qos_fd = open("/dev/cpu_dma_latency", O_RDWR);
	if (pm_qos_fd < 0) {
	   fprintf(stderr, "Failed to open PM QOS file: %s",
	           strerror(errno));
	   exit(errno);
	}
	write(pm_qos_fd, &target, sizeof(target));
}

void stop_low_latency(void)
{
	if (pm_qos_fd >= 0)
	   close(pm_qos_fd);
}

main()

static int pm_qos_fd = -1;

void start_low_latency(void)
{
	s32_t target = 0;

	if (pm_qos_fd >= 0)
		return;
	pm_qos_fd = open("/dev/cpu_dma_latency", O_RDWR);
	if (pm_qos_fd < 0) {
	   fprintf(stderr, "Failed to open PM QOS file: %s",
	           strerror(errno));
	   exit(errno);
	}
	write(pm_qos_fd, &target, sizeof(target));
}

void stop_low_latency(void)
{
	if (pm_qos_fd >= 0)
	   close(pm_qos_fd);
}