new file mode 100644
@@ -0,0 +1,6 @@
+What: /sys/class/leds/<led>/ttyname
+Date: Dec 2020
+KernelVersion: 5.10
+Contact: linux-leds@vger.kernel.org
+Description:
+ Specifies the tty device name of the triggering tty
@@ -144,4 +144,13 @@ config LEDS_TRIGGER_AUDIO
the audio mute and mic-mute changes.
If unsure, say N
+config LEDS_TRIGGER_TTY
+ tristate "LED Trigger for TTY devices"
+ depends on TTY
+ help
+ This allows LEDs to be controlled by activity on ttys which includes
+ serial devices like /dev/ttyS0.
+
+ When build as a module this driver will be called ledtrig-tty.
+
endif # LEDS_TRIGGERS
@@ -15,3 +15,4 @@ obj-$(CONFIG_LEDS_TRIGGER_PANIC) += ledtrig-panic.o
obj-$(CONFIG_LEDS_TRIGGER_NETDEV) += ledtrig-netdev.o
obj-$(CONFIG_LEDS_TRIGGER_PATTERN) += ledtrig-pattern.o
obj-$(CONFIG_LEDS_TRIGGER_AUDIO) += ledtrig-audio.o
+obj-$(CONFIG_LEDS_TRIGGER_TTY) += ledtrig-tty.o
new file mode 100644
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/delay.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <uapi/linux/serial.h>
+
+struct ledtrig_tty_data {
+ struct led_classdev *led_cdev;
+ struct delayed_work dwork;
+ struct mutex mutex;
+ const char *ttyname;
+ struct tty_struct *tty;
+ int rx, tx;
+};
+
+static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
+{
+ schedule_delayed_work(&trigger_data->dwork, 0);
+}
+
+static ssize_t ttyname_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+ ssize_t len = 0;
+
+ mutex_lock(&trigger_data->mutex);
+
+ if (trigger_data->ttyname)
+ len = sprintf(buf, "%s\n", trigger_data->ttyname);
+
+ mutex_unlock(&trigger_data->mutex);
+
+ return len;
+}
+
+static ssize_t ttyname_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);
+ char *ttyname;
+ ssize_t ret = size;
+ bool running;
+
+ if (size > 0 && buf[size - 1] == '\n')
+ size -= 1;
+
+ if (size) {
+ ttyname = kmemdup_nul(buf, size, GFP_KERNEL);
+ if (!ttyname) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+ } else {
+ ttyname = NULL;
+ }
+
+ mutex_lock(&trigger_data->mutex);
+
+ running = trigger_data->ttyname != NULL;
+
+ kfree(trigger_data->ttyname);
+ tty_kref_put(trigger_data->tty);
+ trigger_data->tty = NULL;
+
+ trigger_data->ttyname = ttyname;
+
+out_unlock:
+ mutex_unlock(&trigger_data->mutex);
+
+ if (ttyname && !running)
+ ledtrig_tty_restart(trigger_data);
+
+ return ret;
+}
+static DEVICE_ATTR_RW(ttyname);
+
+static void ledtrig_tty_work(struct work_struct *work)
+{
+ struct ledtrig_tty_data *trigger_data =
+ container_of(work, struct ledtrig_tty_data, dwork.work);
+ struct serial_icounter_struct icount;
+ int ret;
+
+ mutex_lock(&trigger_data->mutex);
+
+ if (!trigger_data->ttyname) {
+ /* exit without rescheduling */
+ mutex_unlock(&trigger_data->mutex);
+ return;
+ }
+
+ /* try to get the tty corresponding to $ttyname */
+ if (!trigger_data->tty) {
+ dev_t devno;
+ struct tty_struct *tty;
+ int ret;
+
+ ret = tty_dev_name_to_number(trigger_data->ttyname, &devno);
+ if (ret < 0)
+ /*
+ * A device with this name might appear later, so keep
+ * retrying.
+ */
+ goto out;
+
+ tty = tty_kopen_shared(devno);
+ if (IS_ERR(tty) || !tty)
+ /* What to do? retry or abort */
+ goto out;
+
+ 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(trigger_data->led_cdev, LED_ON);
+
+ trigger_data->rx = icount.rx;
+ trigger_data->tx = icount.tx;
+ } else {
+ led_set_brightness(trigger_data->led_cdev, LED_OFF);
+ }
+
+out:
+ mutex_unlock(&trigger_data->mutex);
+ schedule_delayed_work(&trigger_data->dwork, msecs_to_jiffies(100));
+}
+
+static struct attribute *ledtrig_tty_attrs[] = {
+ &dev_attr_ttyname.attr,
+ NULL
+};
+ATTRIBUTE_GROUPS(ledtrig_tty);
+
+static int ledtrig_tty_activate(struct led_classdev *led_cdev)
+{
+ struct ledtrig_tty_data *trigger_data;
+
+ trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
+ if (!trigger_data)
+ return -ENOMEM;
+
+ led_set_trigger_data(led_cdev, trigger_data);
+
+ INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
+ trigger_data->led_cdev = led_cdev;
+ mutex_init(&trigger_data->mutex);
+
+ return 0;
+}
+
+static void ledtrig_tty_deactivate(struct led_classdev *led_cdev)
+{
+ struct ledtrig_tty_data *trigger_data = led_get_trigger_data(led_cdev);
+
+ cancel_delayed_work_sync(&trigger_data->dwork);
+
+ kfree(trigger_data);
+}
+
+static struct led_trigger ledtrig_tty = {
+ .name = "tty",
+ .activate = ledtrig_tty_activate,
+ .deactivate = ledtrig_tty_deactivate,
+ .groups = ledtrig_tty_groups,
+};
+module_led_trigger(ledtrig_tty);
+
+MODULE_AUTHOR("Uwe Kleine-König <u.kleine-koenig@pengutronix.de>");
+MODULE_DESCRIPTION("UART LED trigger");
+MODULE_LICENSE("GPL v2");