This is only a proof of concept driver that makes an LED blink on UART
activity. Feedback about the concept is very welcome.
Without-S-o-b-on-purpose-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
drivers/leds/trigger/Kconfig | 7 ++
drivers/leds/trigger/Makefile | 1 +
drivers/leds/trigger/ledtrig-uart.c | 138 ++++++++++++++++++++++++++++
3 files changed, 146 insertions(+)
create mode 100644 drivers/leds/trigger/ledtrig-uart.c
diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 4018af769969..fcea6a87adc7 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -129,4 +129,11 @@ config LEDS_TRIGGER_NETDEV
This allows LEDs to be controlled by network device activity.
If unsure, say Y.
+config LEDS_TRIGGER_UART
+ tristate "LED Trigger for UART devices"
+ depends on SERIAL_CORE
+ help
+ This allows LEDs to be controlled by activity on serial devices like
+ /dev/ttyS0.
+
endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index f3cfe1950538..9e1341b711fd 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT) += ledtrig-transient.o
obj-$(CONFIG_LEDS_TRIGGER_CAMERA) += ledtrig-camera.o
obj-$(CONFIG_LEDS_TRIGGER_PANIC) += ledtrig-panic.o
obj-$(CONFIG_LEDS_TRIGGER_NETDEV) += ledtrig-netdev.o
+obj-$(CONFIG_LEDS_TRIGGER_UART) += ledtrig-uart.o
diff --git a/drivers/leds/trigger/ledtrig-uart.c b/drivers/leds/trigger/ledtrig-uart.c
new file mode 100644
index 000000000000..6f0ece9829de
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-uart.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/module.h>
+#include <linux/leds.h>
+#include <linux/slab.h>
+#include <linux/serial_core.h>
+
+struct ledtrig_uart_data {
+ struct led_classdev *led_cdev;
+ const char *devname;
+ struct delayed_work dwork;
+ struct uart_icount icount;
+};
+
+static void ledtrig_uart_halt(struct ledtrig_uart_data *trigger_data)
+{
+ cancel_delayed_work_sync(&trigger_data->dwork);
+}
+
+static void ledtrig_uart_restart(struct ledtrig_uart_data *trigger_data)
+{
+ pr_info("%s:%d: devname = %s\n", __func__, __LINE__, trigger_data->devname);
+ if (!trigger_data->devname)
+ return;
+
+ schedule_delayed_work(&trigger_data->dwork, 0);
+}
+
+static ssize_t devname_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct ledtrig_uart_data *trigger_data = led_trigger_get_drvdata(dev);
+ ssize_t len;
+
+ len = sprintf(buf, "%s\n", trigger_data->devname);
+
+ return len;
+}
+
+static ssize_t devname_store(struct device *dev,
+ struct device_attribute *attr, const char *buf,
+ size_t size)
+{
+ struct ledtrig_uart_data *trigger_data = led_trigger_get_drvdata(dev);
+ char *devname;
+
+ if (size == 0 || (size == 1 || buf[0] == '\n')) {
+ devname = NULL;
+ } else {
+ devname = kstrndup(buf, size, GFP_KERNEL);
+ if (!devname)
+ return -ENOMEM;
+
+ if (devname[size - 1] == '\n')
+ devname[size - 1] = '\0';
+ }
+
+ ledtrig_uart_halt(trigger_data);
+
+ kfree(trigger_data->devname);
+ trigger_data->devname = devname;
+
+ ledtrig_uart_restart(trigger_data);
+
+ return size;
+}
+static DEVICE_ATTR_RW(devname);
+
+static void ledtrig_uart_work(struct work_struct *work)
+{
+ struct ledtrig_uart_data *trigger_data =
+ container_of(work, struct ledtrig_uart_data, dwork.work);
+ const struct uart_port *port = uart_get_port_by_name(trigger_data->devname);
+
+ pr_info("%s:%d: devname = %s, port = %px\n", __func__, __LINE__, trigger_data->devname, port);
+
+ if (!port) {
+ led_set_brightness(trigger_data->led_cdev, LED_OFF);
+ return;
+ }
+
+ if (port->icount.rx > trigger_data->icount.rx ||
+ port->icount.tx > trigger_data->icount.tx) {
+ unsigned long delay_on = 0, delay_off = 0;
+
+ led_blink_set_oneshot(trigger_data->led_cdev,
+ &delay_on, &delay_off, 0);
+
+ trigger_data->icount = port->icount;
+ }
+
+ schedule_delayed_work(&trigger_data->dwork, msecs_to_jiffies(1000));
+}
+
+static struct attribute *ledtrig_uart_attrs[] = {
+ &dev_attr_devname.attr,
+ NULL
+};
+ATTRIBUTE_GROUPS(ledtrig_uart);
+
+static int ledtrig_uart_activate(struct led_classdev *led_cdev)
+{
+ struct ledtrig_uart_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_uart_work);
+ trigger_data->led_cdev = led_cdev;
+
+ pr_info("%s:%d\n", __func__, __LINE__);
+
+ return 0;
+}
+
+static void ledtrig_uart_deactivate(struct led_classdev *led_cdev)
+{
+ struct ledtrig_uart_data *trigger_data = led_get_trigger_data(led_cdev);
+
+ cancel_delayed_work_sync(&trigger_data->dwork);
+
+ kfree(trigger_data);
+}
+
+struct led_trigger ledtrig_uart = {
+ .name = "uart",
+ .activate = ledtrig_uart_activate,
+ .deactivate = ledtrig_uart_deactivate,
+ .groups = ledtrig_uart_groups,
+};
+module_led_trigger(ledtrig_uart);
+
+MODULE_AUTHOR("Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("UART LED trigger");
+MODULE_LICENSE("GPL v2");
--
2.19.1
