1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/delay.h>
4 #include <linux/leds.h>
5 #include <linux/module.h>
6 #include <linux/slab.h>
8 #include <uapi/linux/serial.h>
10 struct ledtrig_tty_data {
11 struct led_classdev *led_cdev;
12 struct delayed_work dwork;
15 struct tty_struct *tty;
19 static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
21 schedule_delayed_work(&trigger_data->dwork, 0);
24 static ssize_t ttyname_show(struct device *dev,
25 struct device_attribute *attr, char *buf)
27 struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
30 mutex_lock(&trigger_data->mutex);
32 if (trigger_data->ttyname)
33 len = sprintf(buf, "%s\n", trigger_data->ttyname);
35 mutex_unlock(&trigger_data->mutex);
40 static ssize_t ttyname_store(struct device *dev,
41 struct device_attribute *attr, const char *buf,
44 struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
49 if (size > 0 && buf[size - 1] == '\n')
53 ttyname = kmemdup_nul(buf, size, GFP_KERNEL);
62 mutex_lock(&trigger_data->mutex);
64 running = trigger_data->ttyname != NULL;
66 kfree(trigger_data->ttyname);
67 tty_kref_put(trigger_data->tty);
68 trigger_data->tty = NULL;
70 trigger_data->ttyname = ttyname;
73 mutex_unlock(&trigger_data->mutex);
75 if (ttyname && !running)
76 ledtrig_tty_restart(trigger_data);
80 static DEVICE_ATTR_RW(ttyname);
82 static void ledtrig_tty_work(struct work_struct *work)
84 struct ledtrig_tty_data *trigger_data =
85 container_of(work, struct ledtrig_tty_data, dwork.work);
86 struct serial_icounter_struct icount;
89 mutex_lock(&trigger_data->mutex);
91 if (!trigger_data->ttyname) {
92 /* exit without rescheduling */
93 mutex_unlock(&trigger_data->mutex);
97 /* try to get the tty corresponding to $ttyname */
98 if (!trigger_data->tty) {
100 struct tty_struct *tty;
103 ret = tty_dev_name_to_number(trigger_data->ttyname, &devno);
106 * A device with this name might appear later, so keep
111 tty = tty_kopen_shared(devno);
112 if (IS_ERR(tty) || !tty)
113 /* What to do? retry or abort */
116 trigger_data->tty = tty;
119 ret = tty_get_icount(trigger_data->tty, &icount);
121 dev_info(trigger_data->tty->dev, "Failed to get icount, stopped polling\n");
122 mutex_unlock(&trigger_data->mutex);
126 if (icount.rx != trigger_data->rx ||
127 icount.tx != trigger_data->tx) {
128 led_set_brightness(trigger_data->led_cdev, LED_ON);
130 trigger_data->rx = icount.rx;
131 trigger_data->tx = icount.tx;
133 led_set_brightness(trigger_data->led_cdev, LED_OFF);
137 mutex_unlock(&trigger_data->mutex);
138 schedule_delayed_work(&trigger_data->dwork, msecs_to_jiffies(100));
141 static struct attribute *ledtrig_tty_attrs[] = {
142 &dev_attr_ttyname.attr,
145 ATTRIBUTE_GROUPS(ledtrig_tty);
147 static int ledtrig_tty_activate(struct led_classdev *led_cdev)
149 struct ledtrig_tty_data *trigger_data;
151 trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
155 led_set_trigger_data(led_cdev, trigger_data);
157 INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
158 trigger_data->led_cdev = led_cdev;
159 mutex_init(&trigger_data->mutex);
164 static void ledtrig_tty_deactivate(struct led_classdev *led_cdev)
166 struct ledtrig_tty_data *trigger_data = led_get_trigger_data(led_cdev);
168 cancel_delayed_work_sync(&trigger_data->dwork);
173 static struct led_trigger ledtrig_tty = {
175 .activate = ledtrig_tty_activate,
176 .deactivate = ledtrig_tty_deactivate,
177 .groups = ledtrig_tty_groups,
179 module_led_trigger(ledtrig_tty);
181 MODULE_AUTHOR("Uwe Kleine-König <u.kleine-koenig@pengutronix.de>");
182 MODULE_DESCRIPTION("UART LED trigger");
183 MODULE_LICENSE("GPL v2");