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Uwe Kleine-Königgregkh
Uwe Kleine-König
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gregkh
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leds: trigger: implement a tty trigger
Usage is as follows: myled=ledname tty=ttyS0 echo tty > /sys/class/leds/$myled/trigger echo $tty > /sys/class/leds/$myled/ttyname . 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 <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]>
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‎Documentation/ABI/testing/sysfs-class-led-trigger-tty

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What: /sys/class/leds/<led>/ttyname
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Date: Dec 2020
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KernelVersion: 5.10
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Contact: [email protected]
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Description:
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Specifies the tty device name of the triggering tty

‎drivers/leds/trigger/Kconfig

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@@ -144,4 +144,13 @@ config LEDS_TRIGGER_AUDIO
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the audio mute and mic-mute changes.
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If unsure, say N
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config LEDS_TRIGGER_TTY
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tristate "LED Trigger for TTY devices"
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depends on TTY
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help
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This allows LEDs to be controlled by activity on ttys which includes
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serial devices like /dev/ttyS0.
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When build as a module this driver will be called ledtrig-tty.
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endif # LEDS_TRIGGERS

‎drivers/leds/trigger/Makefile

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@@ -15,3 +15,4 @@ obj-$(CONFIG_LEDS_TRIGGER_PANIC) += ledtrig-panic.o
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obj-$(CONFIG_LEDS_TRIGGER_NETDEV) += ledtrig-netdev.o
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obj-$(CONFIG_LEDS_TRIGGER_PATTERN) += ledtrig-pattern.o
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obj-$(CONFIG_LEDS_TRIGGER_AUDIO) += ledtrig-audio.o
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obj-$(CONFIG_LEDS_TRIGGER_TTY) += ledtrig-tty.o

‎drivers/leds/trigger/ledtrig-tty.c

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// SPDX-License-Identifier: GPL-2.0
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#include <linux/delay.h>
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#include <linux/leds.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/tty.h>
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#include <uapi/linux/serial.h>
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struct ledtrig_tty_data {
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struct led_classdev *led_cdev;
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struct delayed_work dwork;
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struct mutex mutex;
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const char *ttyname;
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struct tty_struct *tty;
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int rx, tx;
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};
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static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
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{
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schedule_delayed_work(&trigger_data->dwork, 0);
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}
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static ssize_t ttyname_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
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ssize_t len = 0;
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mutex_lock(&trigger_data->mutex);
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if (trigger_data->ttyname)
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len = sprintf(buf, "%s\n", trigger_data->ttyname);
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mutex_unlock(&trigger_data->mutex);
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return len;
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}
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static ssize_t ttyname_store(struct device *dev,
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struct device_attribute *attr, const char *buf,
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size_t size)
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{
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struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
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char *ttyname;
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ssize_t ret = size;
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bool running;
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if (size > 0 && buf[size - 1] == '\n')
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size -= 1;
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if (size) {
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ttyname = kmemdup_nul(buf, size, GFP_KERNEL);
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if (!ttyname) {
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ret = -ENOMEM;
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goto out_unlock;
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}
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} else {
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ttyname = NULL;
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}
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mutex_lock(&trigger_data->mutex);
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running = trigger_data->ttyname != NULL;
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kfree(trigger_data->ttyname);
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tty_kref_put(trigger_data->tty);
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trigger_data->tty = NULL;
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trigger_data->ttyname = ttyname;
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out_unlock:
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mutex_unlock(&trigger_data->mutex);
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if (ttyname && !running)
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ledtrig_tty_restart(trigger_data);
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return ret;
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}
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static DEVICE_ATTR_RW(ttyname);
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static void ledtrig_tty_work(struct work_struct *work)
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{
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struct ledtrig_tty_data *trigger_data =
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container_of(work, struct ledtrig_tty_data, dwork.work);
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struct serial_icounter_struct icount;
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int ret;
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mutex_lock(&trigger_data->mutex);
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if (!trigger_data->ttyname) {
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/* exit without rescheduling */
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mutex_unlock(&trigger_data->mutex);
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return;
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}
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/* try to get the tty corresponding to $ttyname */
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if (!trigger_data->tty) {
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dev_t devno;
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struct tty_struct *tty;
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int ret;
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ret = tty_dev_name_to_number(trigger_data->ttyname, &devno);
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if (ret < 0)
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/*
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* A device with this name might appear later, so keep
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* retrying.
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*/
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goto out;
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tty = tty_kopen_shared(devno);
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if (IS_ERR(tty) || !tty)
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/* What to do? retry or abort */
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goto out;
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trigger_data->tty = tty;
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}
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ret = tty_get_icount(trigger_data->tty, &icount);
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if (ret) {
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dev_info(trigger_data->tty->dev, "Failed to get icount, stopped polling\n");
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mutex_unlock(&trigger_data->mutex);
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return;
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}
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if (icount.rx != trigger_data->rx ||
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icount.tx != trigger_data->tx) {
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led_set_brightness(trigger_data->led_cdev, LED_ON);
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trigger_data->rx = icount.rx;
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trigger_data->tx = icount.tx;
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} else {
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led_set_brightness(trigger_data->led_cdev, LED_OFF);
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}
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out:
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mutex_unlock(&trigger_data->mutex);
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schedule_delayed_work(&trigger_data->dwork, msecs_to_jiffies(100));
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}
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static struct attribute *ledtrig_tty_attrs[] = {
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&dev_attr_ttyname.attr,
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NULL
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};
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ATTRIBUTE_GROUPS(ledtrig_tty);
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static int ledtrig_tty_activate(struct led_classdev *led_cdev)
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{
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struct ledtrig_tty_data *trigger_data;
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trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
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if (!trigger_data)
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return -ENOMEM;
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led_set_trigger_data(led_cdev, trigger_data);
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INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
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trigger_data->led_cdev = led_cdev;
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mutex_init(&trigger_data->mutex);
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return 0;
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}
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static void ledtrig_tty_deactivate(struct led_classdev *led_cdev)
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{
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struct ledtrig_tty_data *trigger_data = led_get_trigger_data(led_cdev);
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cancel_delayed_work_sync(&trigger_data->dwork);
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kfree(trigger_data);
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}
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static struct led_trigger ledtrig_tty = {
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.name = "tty",
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.activate = ledtrig_tty_activate,
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.deactivate = ledtrig_tty_deactivate,
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.groups = ledtrig_tty_groups,
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};
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module_led_trigger(ledtrig_tty);
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MODULE_AUTHOR("Uwe Kleine-König <[email protected]>");
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MODULE_DESCRIPTION("UART LED trigger");
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MODULE_LICENSE("GPL v2");

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