[v6,7/7] leds: ledtrig-tty: add additional line state evaluation

diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-tty b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
index 504dece151b8..30cef9ac0f49 100644
--- a/Documentation/ABI/testing/sysfs-class-led-trigger-tty
+++ b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
@@ -20,3 +20,43 @@  Description:
 		Signal transmission (tx) of data on the named tty device.
 		If set to 0, the LED will not blink on transmission.
 		If set to 1 (default), the LED will blink on transmission.
+
+What:		/sys/class/leds/<led>/cts
+Date:		February 2024
+KernelVersion:	6.8
+Description:
+		CTS = Clear To Send
+		DCE is ready to accept data from the DTE.
+		If the line state is detected, the LED is switched on.
+		If set to 0 (default), the LED will not evaluate CTS.
+		If set to 1, the LED will evaluate CTS.
+
+What:		/sys/class/leds/<led>/dsr
+Date:		February 2024
+KernelVersion:	6.8
+Description:
+		DSR = Data Set Ready
+		DCE is ready to receive and send data.
+		If the line state is detected, the LED is switched on.
+		If set to 0 (default), the LED will not evaluate DSR.
+		If set to 1, the LED will evaluate DSR.
+
+What:		/sys/class/leds/<led>/dcd
+Date:		February 2024
+KernelVersion:	6.8
+Description:
+		DCD = Data Carrier Detect
+		DTE is receiving a carrier from the DCE.
+		If the line state is detected, the LED is switched on.
+		If set to 0 (default), the LED will not evaluate CAR (DCD).
+		If set to 1, the LED will evaluate CAR (DCD).
+
+What:		/sys/class/leds/<led>/rng
+Date:		February 2024
+KernelVersion:	6.8
+Description:
+		RNG = Ring Indicator
+		DCE has detected an incoming ring signal on the telephone
+		line. If the line state is detected, the LED is switched on.
+		If set to 0 (default), the LED will not evaluate RNG.
+		If set to 1, the LED will evaluate RNG.
diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
index 1a40a78bf1ee..a364b7ca38c8 100644
--- a/drivers/leds/trigger/ledtrig-tty.c
+++ b/drivers/leds/trigger/ledtrig-tty.c
@@ -19,17 +19,26 @@  struct ledtrig_tty_data {
 	int rx, tx;
 	bool mode_rx;
 	bool mode_tx;
+	bool mode_cts;
+	bool mode_dsr;
+	bool mode_dcd;
+	bool mode_rng;
 };
 
 /* Indicates which state the LED should now display */
 enum led_trigger_tty_state {
 	TTY_LED_BLINK,
+	TTY_LED_ENABLE,
 	TTY_LED_DISABLE,
 };
 
 enum led_trigger_tty_modes {
 	TRIGGER_TTY_RX = 0,
 	TRIGGER_TTY_TX,
+	TRIGGER_TTY_CTS,
+	TRIGGER_TTY_DSR,
+	TRIGGER_TTY_DCD,
+	TRIGGER_TTY_RNG,
 };
 
 static int ledtrig_tty_waitforcompletion(struct device *dev)
@@ -118,6 +127,18 @@  static ssize_t ledtrig_tty_attr_show(struct device *dev, char *buf,
 	case TRIGGER_TTY_TX:
 		state = trigger_data->mode_tx;
 		break;
+	case TRIGGER_TTY_CTS:
+		state = trigger_data->mode_cts;
+		break;
+	case TRIGGER_TTY_DSR:
+		state = trigger_data->mode_dsr;
+		break;
+	case TRIGGER_TTY_DCD:
+		state = trigger_data->mode_dcd;
+		break;
+	case TRIGGER_TTY_RNG:
+		state = trigger_data->mode_rng;
+		break;
 	}
 
 	return sysfs_emit(buf, "%u\n", state);
@@ -147,6 +168,18 @@  static ssize_t ledtrig_tty_attr_store(struct device *dev, const char *buf,
 	case TRIGGER_TTY_TX:
 		trigger_data->mode_tx = state;
 		break;
+	case TRIGGER_TTY_CTS:
+		trigger_data->mode_cts = state;
+		break;
+	case TRIGGER_TTY_DSR:
+		trigger_data->mode_dsr = state;
+		break;
+	case TRIGGER_TTY_DCD:
+		trigger_data->mode_dcd = state;
+		break;
+	case TRIGGER_TTY_RNG:
+		trigger_data->mode_rng = state;
+		break;
 	}
 
 	return size;
@@ -167,6 +200,10 @@  static ssize_t ledtrig_tty_attr_store(struct device *dev, const char *buf,
 
 DEFINE_TTY_TRIGGER(rx, TRIGGER_TTY_RX);
 DEFINE_TTY_TRIGGER(tx, TRIGGER_TTY_TX);
+DEFINE_TTY_TRIGGER(cts, TRIGGER_TTY_CTS);
+DEFINE_TTY_TRIGGER(dsr, TRIGGER_TTY_DSR);
+DEFINE_TTY_TRIGGER(dcd, TRIGGER_TTY_DCD);
+DEFINE_TTY_TRIGGER(rng, TRIGGER_TTY_RNG);
 
 static void ledtrig_tty_work(struct work_struct *work)
 {
@@ -175,6 +212,7 @@  static void ledtrig_tty_work(struct work_struct *work)
 	struct led_classdev *led_cdev = trigger_data->led_cdev;
 	enum led_trigger_tty_state state = TTY_LED_DISABLE;
 	unsigned long interval = LEDTRIG_TTY_INTERVAL;
+	int status;
 	int ret;
 
 	if (!trigger_data->ttyname)
@@ -202,6 +240,33 @@  static void ledtrig_tty_work(struct work_struct *work)
 		trigger_data->tty = tty;
 	}
 
+	status = tty_get_tiocm(trigger_data->tty);
+	if (status > 0) {
+		if (trigger_data->mode_cts) {
+			if (status & TIOCM_CTS)
+				state = TTY_LED_ENABLE;
+		}
+
+		if (trigger_data->mode_dsr) {
+			if (status & TIOCM_DSR)
+				state = TTY_LED_ENABLE;
+		}
+
+		if (trigger_data->mode_dcd) {
+			if (status & TIOCM_CAR)
+				state = TTY_LED_ENABLE;
+		}
+
+		if (trigger_data->mode_rng) {
+			if (status & TIOCM_RNG)
+				state = TTY_LED_ENABLE;
+		}
+	}
+
+	/*
+	 * The evaluation of rx/tx must be done after the evaluation
+	 * of TIOCM_*, because rx/tx has priority.
+	 */
 	if (trigger_data->mode_rx || trigger_data->mode_tx) {
 		struct serial_icounter_struct icount;
 
@@ -225,6 +290,9 @@  static void ledtrig_tty_work(struct work_struct *work)
 	case TTY_LED_BLINK:
 		led_blink_set_oneshot(led_cdev, &interval, &interval, 0);
 		break;
+	case TTY_LED_ENABLE:
+		led_set_brightness(led_cdev, led_cdev->blink_brightness);
+		break;
 	case TTY_LED_DISABLE:
 		fallthrough;
 	default:
@@ -241,6 +309,10 @@  static struct attribute *ledtrig_tty_attrs[] = {
 	&dev_attr_ttyname.attr,
 	&dev_attr_rx.attr,
 	&dev_attr_tx.attr,
+	&dev_attr_cts.attr,
+	&dev_attr_dsr.attr,
+	&dev_attr_dcd.attr,
+	&dev_attr_rng.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(ledtrig_tty);