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// 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");
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