[PATCH 2/2] leds: trigger: ledtrig-tty: add additional modes

Florian Eckert
2023-02-13T14:23:03Z

Add additional modes to trigger the selected LED.
The following modes are supported:

TD/RD: Flash LED on data transmission (default)
CTS: DCE Ready to accept data from the DTE.
DSR: DCE is ready to receive and send data.
CAR: DCE is receiving a carrier from a remote DTE.
RNG: DCE has detected an incoming ring signal.

The mode can be changed for example with the following command:
echo "CTS" /sys/class/leds/<led>/mode

This would turn on the LED, when the DTE(modem) signals the DCE that it
is ready to accept data.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
---
.../ABI/testing/sysfs-class-led-trigger-tty | 16 ++
drivers/leds/trigger/ledtrig-tty.c | 148 ++++++++++++++++--
2 files changed, 149 insertions(+), 15 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-tty b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
index 2bf6b24e781b..bb6333ed7028 100644
--- a/Documentation/ABI/testing/sysfs-class-led-trigger-tty
+++ b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
@@ -4,3 +4,19 @@ KernelVersion: 5.10
Contact: linux-leds@vger.kernel.org
Description:
Specifies the tty device name of the triggering tty
+
+What: /sys/class/leds/<led>/mode
+Date: January 2023
+KernelVersion: 6.3
+Description:
+ Specifies the operating to trigger the LED.
+ The following operating modes are supported:
+ TD/RD: Flash LED on data transmission (default)
+ CTS: DCE Ready to accept data from the DTE.
+ LED on if line is high.
+ DSR: DCE is ready to receive and send data.
+ LED on if line is high.
+ CAR: DCE is receiving a carrier from a remote DTE.
+ LED on if line is high.
+ RNG: DCE has detected an incoming ring signal.
+ LED on if line is high.
diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
index f62db7e520b5..152b3020998e 100644
--- a/drivers/leds/trigger/ledtrig-tty.c
+++ b/drivers/leds/trigger/ledtrig-tty.c
@@ -7,6 +7,14 @@
#include <linux/tty.h>
#include <uapi/linux/serial.h>

+enum tty_led_mode {
+ TTY_LED_CNT,
+ TTY_LED_CTS,
+ TTY_LED_DSR,
+ TTY_LED_CAR,
+ TTY_LED_RNG,
+};
+
struct ledtrig_tty_data {
struct led_classdev *led_cdev;
struct delayed_work dwork;
@@ -14,6 +22,15 @@ struct ledtrig_tty_data {
const char *ttyname;
struct tty_struct *tty;
int rx, tx;
+ unsigned int mode;
+};
+
+static const char * const mode[] = {
+ [TTY_LED_CNT] = "TD/RD", // Trasmit Data / Receive Data
+ [TTY_LED_CTS] = "CTS", // CTS Clear To Send
+ [TTY_LED_DSR] = "DSR", // DSR Data Set Ready
+ [TTY_LED_CAR] = "CAR", // CAR Data Carrier Detect (DCD)
+ [TTY_LED_RNG] = "RNG", // RNG Ring Indicator (RI)
};

static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
@@ -21,6 +38,74 @@ static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
schedule_delayed_work(&trigger_data->dwork, 0);
}

+static ssize_t mode_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+ enum tty_led_mode tty_mode;
+
+ mutex_lock(&trigger_data->mutex);
+ tty_mode = trigger_data->mode;
+ mutex_unlock(&trigger_data->mutex);
+
+ switch (tty_mode) {
+ case TTY_LED_CTS:
+ return sprintf(buf, "%s [%s] %s %s %s\n", mode[TTY_LED_CNT],
+ mode[TTY_LED_CTS], mode[TTY_LED_DSR],
+ mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
+ case TTY_LED_DSR:
+ return sprintf(buf, "%s %s [%s] %s %s\n", mode[TTY_LED_CNT],
+ mode[TTY_LED_CTS], mode[TTY_LED_DSR],
+ mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
+ case TTY_LED_CAR:
+ return sprintf(buf, "%s %s %s [%s] %s\n", mode[TTY_LED_CNT],
+ mode[TTY_LED_CTS], mode[TTY_LED_DSR],
+ mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
+ case TTY_LED_RNG:
+ return sprintf(buf, "%s %s %s %s [%s]\n", mode[TTY_LED_CNT],
+ mode[TTY_LED_CTS], mode[TTY_LED_DSR],
+ mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
+ case TTY_LED_CNT:
+ default:
+ return sprintf(buf, "[%s] %s %s %s %s\n", mode[TTY_LED_CNT],
+ mode[TTY_LED_CTS], mode[TTY_LED_DSR],
+ mode[TTY_LED_CAR], mode[TTY_LED_RNG]);
+ }
+}
+
+static ssize_t mode_store(struct device *dev,
+ struct device_attribute *attr, const char *buf,
+ size_t size)
+{
+ struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+ ssize_t ret = size;
+ enum tty_led_mode tty_mode;
+
+ /* Check for new line in string*/
+ if (size > 0 && buf[size - 1] == '\n')
+ size -= 1;
+
+ if (strncmp(buf, mode[TTY_LED_CTS], size) == 0)
+ tty_mode = TTY_LED_CTS;
+ else if (strncmp(buf, mode[TTY_LED_DSR], size) == 0)
+ tty_mode = TTY_LED_DSR;
+ else if (strncmp(buf, mode[TTY_LED_CAR], size) == 0)
+ tty_mode = TTY_LED_CAR;
+ else if (strncmp(buf, mode[TTY_LED_RNG], size) == 0)
+ tty_mode = TTY_LED_RNG;
+ else if (strncmp(buf, mode[TTY_LED_CNT], size) == 0)
+ tty_mode = TTY_LED_CNT;
+ else
+ return -EINVAL;
+
+ mutex_lock(&trigger_data->mutex);
+ trigger_data->mode = tty_mode;
+ mutex_unlock(&trigger_data->mutex);
+
+ return ret;
+}
+static DEVICE_ATTR_RW(mode);
+
static ssize_t ttyname_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -76,6 +161,18 @@ static ssize_t ttyname_store(struct device *dev,
}
static DEVICE_ATTR_RW(ttyname);

+static void ledtrig_tty_flags(struct ledtrig_tty_data *trigger_data,
+ unsigned int flag)
+{
+ unsigned int status;
+
+ status = tty_get_mget(trigger_data->tty);
+ if (status & flag)
+ led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
+ else
+ led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+}
+
static void ledtrig_tty_work(struct work_struct *work)
{
struct ledtrig_tty_data *trigger_data =
@@ -113,21 +210,38 @@ static void ledtrig_tty_work(struct work_struct *work)
trigger_data->tty = tty;
}

- ret = tty_get_icount(trigger_data->tty, &icount);
- if (ret) {
- dev_info(trigger_data->tty->dev, "Failed to get icount, stopped polling\n");
- mutex_unlock(&trigger_data->mutex);
- return;
- }
-
- if (icount.rx != trigger_data->rx ||
- icount.tx != trigger_data->tx) {
- led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
-
- trigger_data->rx = icount.rx;
- trigger_data->tx = icount.tx;
- } else {
- led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+ switch (trigger_data->mode) {
+ case TTY_LED_CTS:
+ ledtrig_tty_flags(trigger_data, TIOCM_CTS);
+ break;
+ case TTY_LED_DSR:
+ ledtrig_tty_flags(trigger_data, TIOCM_DSR);
+ break;
+ case TTY_LED_CAR:
+ ledtrig_tty_flags(trigger_data, TIOCM_CAR);
+ break;
+ case TTY_LED_RNG:
+ ledtrig_tty_flags(trigger_data, TIOCM_RNG);
+ break;
+ case TTY_LED_CNT:
+ default:
+ ret = tty_get_icount(trigger_data->tty, &icount);
+ if (ret) {
+ dev_info(trigger_data->tty->dev, "Failed to get icount, stopped polling\n");
+ mutex_unlock(&trigger_data->mutex);
+ return;
+ }
+
+ if (icount.rx != trigger_data->rx ||
+ icount.tx != trigger_data->tx) {
+ led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
+
+ trigger_data->rx = icount.rx;
+ trigger_data->tx = icount.tx;
+ } else {
+ led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
+ }
+ break;
}

out:
@@ -137,6 +251,7 @@ static void ledtrig_tty_work(struct work_struct *work)

static struct attribute *ledtrig_tty_attrs[] = {
&dev_attr_ttyname.attr,
+ &dev_attr_mode.attr,
NULL
};
ATTRIBUTE_GROUPS(ledtrig_tty);
@@ -149,6 +264,9 @@ static int ledtrig_tty_activate(struct led_classdev *led_cdev)
if (!trigger_data)
return -ENOMEM;

+ /* set default mode */
+ trigger_data->mode = TTY_LED_CNT;
+
led_set_trigger_data(led_cdev, trigger_data);

INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
--
2.30.2