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Subject[PATCH v5 3/3] leds: trigger: implement a tty trigger
Date
Usage is as follows:

myled=ledname
tty=ttyS0

echo tty > /sys/class/leds/$myled/trigger
cat /sys/class/tty/$tty/dev > /sys/class/leds/$myled/dev

. When this new trigger is active it periodically checks the tty's
statistics and when it changed since the last check the led is flashed
once.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
.../ABI/testing/sysfs-class-led-trigger-tty | 6 +
drivers/leds/trigger/Kconfig | 7 +
drivers/leds/trigger/Makefile | 1 +
drivers/leds/trigger/ledtrig-tty.c | 153 ++++++++++++++++++
4 files changed, 167 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-class-led-trigger-tty
create mode 100644 drivers/leds/trigger/ledtrig-tty.c

diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-tty b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
new file mode 100644
index 000000000000..f56f9721c317
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led-trigger-tty
@@ -0,0 +1,6 @@
+What: /sys/class/leds/<led>/dev
+Date: Dec 2019
+KernelVersion: 5.6
+Contact: linux-leds@vger.kernel.org
+Description:
+ Specifies $major:$minor of the triggering tty
diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index ce9429ca6dde..40ff08c93f56 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -144,4 +144,11 @@ 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.
+
endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index 733a83e2a718..25c4db97cdd4 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -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
diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
new file mode 100644
index 000000000000..e9bbad52cc3f
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-tty.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#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 tty_struct *tty;
+ dev_t device;
+ int rx, tx;
+};
+
+static void ledtrig_tty_halt(struct ledtrig_tty_data *trigger_data)
+{
+ cancel_delayed_work_sync(&trigger_data->dwork);
+}
+
+static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
+{
+ schedule_delayed_work(&trigger_data->dwork, 0);
+}
+
+static ssize_t dev_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;
+
+ if (trigger_data->tty)
+ len = sprintf(buf, "%d:%d\n", MAJOR(trigger_data->device),
+ MINOR(trigger_data->device));
+
+ return len;
+}
+
+static ssize_t dev_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);
+ struct tty_struct *tty;
+ unsigned major, minor;
+ int ret;
+
+ if (size == 0 || (size == 1 && buf[0] == '\n')) {
+ tty = NULL;
+ } else {
+ ret = sscanf(buf, "%u:%u", &major, &minor);
+ if (ret < 2)
+ return -EINVAL;
+
+ tty = tty_kopen_shared(MKDEV(major, minor));
+ if (IS_ERR(tty))
+ return PTR_ERR(tty);
+ }
+
+ ledtrig_tty_halt(trigger_data);
+
+ tty_kref_put(trigger_data->tty);
+ trigger_data->tty = tty;
+ trigger_data->device = MKDEV(major, minor);
+
+ if (tty) {
+ struct serial_icounter_struct icount;
+ ret = tty_get_icount(trigger_data->tty, &icount);
+ if (!ret) {
+ trigger_data->tx = icount.tx;
+ trigger_data->rx = icount.rx;
+ }
+
+ ledtrig_tty_restart(trigger_data);
+ }
+
+ return size;
+}
+static DEVICE_ATTR_RW(dev);
+
+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;
+
+ if (!trigger_data->tty) {
+ led_set_brightness(trigger_data->led_cdev, LED_OFF);
+ return;
+ }
+
+ ret = tty_get_icount(trigger_data->tty, &icount);
+ if (ret)
+ return;
+
+ if (icount.rx != trigger_data->rx ||
+ icount.tx != trigger_data->tx) {
+ unsigned long delay_on = 100, delay_off = 100;
+
+ led_blink_set_oneshot(trigger_data->led_cdev,
+ &delay_on, &delay_off, 0);
+
+ trigger_data->rx = icount.rx;
+ trigger_data->tx = icount.tx;
+ }
+
+ schedule_delayed_work(&trigger_data->dwork, msecs_to_jiffies(100));
+}
+
+static struct attribute *ledtrig_tty_attrs[] = {
+ &dev_attr_dev.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;
+
+ 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);
+}
+
+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");
--
2.24.0
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