關掉 uart 的功能

要求關掉 uart 的功能，
簡單追一下 kernel code
發現應該可以從userspace改，結果…不如預其

code: copy form here

/* show_msm_console - provide per-port serial console state. */
static ssize_t show_msm_console(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	int enable;
	struct uart_port *port;
	struct platform_device *pdev = to_platform_device(dev);
	port = get_port_from_line(get_line(pdev));
	enable = get_console_state(port);
	return snprintf(buf, sizeof(enable), "%d\n", enable);
}
/*
 * set_msm_console - allow to enable/disable serial console on port.
 *
 * writing 1 enables serial console on UART port.
 * writing 0 disables serial console on UART port.
 */
static ssize_t set_msm_console(struct device *dev,
				struct device_attribute *attr,
				const char *buf, size_t count)
{
	int enable, cur_state;
	struct uart_port *port;
	struct platform_device *pdev = to_platform_device(dev);
	port = get_port_from_line(get_line(pdev));
	cur_state = get_console_state(port);
	enable = buf[0] - '0';
	if (enable == cur_state)
		return count;
	switch (enable) {
	case 0:
		pr_debug("Calling stop_console\n");
		console_stop(port->cons);
		pr_debug("Calling unregister_console\n");
		unregister_console(port->cons);
		pm_runtime_put_sync(&pdev->dev);
		pm_runtime_disable(&pdev->dev);
		/*
		 * Disable UART Core clk
		 * 3 - to disable the UART clock
		 * Thid parameter is not used here, but used in serial core.
		 */
		msm_hsl_power(port, 3, 1);
		break;
	case 1:
		pr_debug("Calling register_console\n");
		/*
		 * Disable UART Core clk
		 * 0 - to enable the UART clock
		 * Thid parameter is not used here, but used in serial core.
		 */
		msm_hsl_power(port, 0, 1);
		pm_runtime_enable(&pdev->dev);
		register_console(port->cons);
		break;
	default:
		return -EINVAL;
	}
	return count;
}
static DEVICE_ATTR(console, S_IWUSR | S_IRUGO, show_msm_console,
						set_msm_console);

platform_device是在 /sys/devices/，
因沒有 grep，這樣範圍太大
後來再 /sys/class/tty，有找到ttyHSL0
有個軟連結 device，就能連到目標/sys/devices/soc/78af000.serial,
也找到 console 了，可以 RW,
但， echo 0 > consle 後，就當機了...
只能換個暴力的方法了...