xref: /linux/drivers/leds/trigger/ledtrig-tty.c (revision ea518afc992032f7570c0a89ac9240b387dc0faf)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <linux/completion.h>
4 #include <linux/delay.h>
5 #include <linux/leds.h>
6 #include <linux/module.h>
7 #include <linux/slab.h>
8 #include <linux/tty.h>
9 #include <uapi/linux/serial.h>
10 
11 #define LEDTRIG_TTY_INTERVAL	50
12 
13 struct ledtrig_tty_data {
14 	struct led_classdev *led_cdev;
15 	struct delayed_work dwork;
16 	struct completion sysfs;
17 	const char *ttyname;
18 	struct tty_struct *tty;
19 	int rx, tx;
20 	bool mode_rx;
21 	bool mode_tx;
22 	bool mode_cts;
23 	bool mode_dsr;
24 	bool mode_dcd;
25 	bool mode_rng;
26 };
27 
28 /* Indicates which state the LED should now display */
29 enum led_trigger_tty_state {
30 	TTY_LED_BLINK,
31 	TTY_LED_ENABLE,
32 	TTY_LED_DISABLE,
33 };
34 
35 enum led_trigger_tty_modes {
36 	TRIGGER_TTY_RX = 0,
37 	TRIGGER_TTY_TX,
38 	TRIGGER_TTY_CTS,
39 	TRIGGER_TTY_DSR,
40 	TRIGGER_TTY_DCD,
41 	TRIGGER_TTY_RNG,
42 };
43 
44 static int ledtrig_tty_wait_for_completion(struct device *dev)
45 {
46 	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
47 	int ret;
48 
49 	ret = wait_for_completion_timeout(&trigger_data->sysfs,
50 					  msecs_to_jiffies(LEDTRIG_TTY_INTERVAL * 20));
51 	if (ret == 0)
52 		return -ETIMEDOUT;
53 
54 	return ret;
55 }
56 
57 static ssize_t ttyname_show(struct device *dev,
58 			    struct device_attribute *attr, char *buf)
59 {
60 	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
61 	ssize_t len = 0;
62 	int completion;
63 
64 	reinit_completion(&trigger_data->sysfs);
65 	completion = ledtrig_tty_wait_for_completion(dev);
66 	if (completion < 0)
67 		return completion;
68 
69 	if (trigger_data->ttyname)
70 		len = sprintf(buf, "%s\n", trigger_data->ttyname);
71 
72 	return len;
73 }
74 
75 static ssize_t ttyname_store(struct device *dev,
76 			     struct device_attribute *attr, const char *buf,
77 			     size_t size)
78 {
79 	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
80 	char *ttyname;
81 	ssize_t ret = size;
82 	int completion;
83 
84 	if (size > 0 && buf[size - 1] == '\n')
85 		size -= 1;
86 
87 	if (size) {
88 		ttyname = kmemdup_nul(buf, size, GFP_KERNEL);
89 		if (!ttyname)
90 			return -ENOMEM;
91 	} else {
92 		ttyname = NULL;
93 	}
94 
95 	reinit_completion(&trigger_data->sysfs);
96 	completion = ledtrig_tty_wait_for_completion(dev);
97 	if (completion < 0)
98 		return completion;
99 
100 	kfree(trigger_data->ttyname);
101 	tty_kref_put(trigger_data->tty);
102 	trigger_data->tty = NULL;
103 
104 	trigger_data->ttyname = ttyname;
105 
106 	return ret;
107 }
108 static DEVICE_ATTR_RW(ttyname);
109 
110 static ssize_t ledtrig_tty_attr_show(struct device *dev, char *buf,
111 				     enum led_trigger_tty_modes attr)
112 {
113 	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
114 	bool state;
115 
116 	switch (attr) {
117 	case TRIGGER_TTY_RX:
118 		state = trigger_data->mode_rx;
119 		break;
120 	case TRIGGER_TTY_TX:
121 		state = trigger_data->mode_tx;
122 		break;
123 	case TRIGGER_TTY_CTS:
124 		state = trigger_data->mode_cts;
125 		break;
126 	case TRIGGER_TTY_DSR:
127 		state = trigger_data->mode_dsr;
128 		break;
129 	case TRIGGER_TTY_DCD:
130 		state = trigger_data->mode_dcd;
131 		break;
132 	case TRIGGER_TTY_RNG:
133 		state = trigger_data->mode_rng;
134 		break;
135 	}
136 
137 	return sysfs_emit(buf, "%u\n", state);
138 }
139 
140 static ssize_t ledtrig_tty_attr_store(struct device *dev, const char *buf,
141 				      size_t size, enum led_trigger_tty_modes attr)
142 {
143 	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
144 	bool state;
145 	int ret;
146 
147 	ret = kstrtobool(buf, &state);
148 	if (ret)
149 		return ret;
150 
151 	switch (attr) {
152 	case TRIGGER_TTY_RX:
153 		trigger_data->mode_rx = state;
154 		break;
155 	case TRIGGER_TTY_TX:
156 		trigger_data->mode_tx = state;
157 		break;
158 	case TRIGGER_TTY_CTS:
159 		trigger_data->mode_cts = state;
160 		break;
161 	case TRIGGER_TTY_DSR:
162 		trigger_data->mode_dsr = state;
163 		break;
164 	case TRIGGER_TTY_DCD:
165 		trigger_data->mode_dcd = state;
166 		break;
167 	case TRIGGER_TTY_RNG:
168 		trigger_data->mode_rng = state;
169 		break;
170 	}
171 
172 	return size;
173 }
174 
175 #define DEFINE_TTY_TRIGGER(trigger_name, trigger) \
176 	static ssize_t trigger_name##_show(struct device *dev, \
177 		struct device_attribute *attr, char *buf) \
178 	{ \
179 		return ledtrig_tty_attr_show(dev, buf, trigger); \
180 	} \
181 	static ssize_t trigger_name##_store(struct device *dev, \
182 		struct device_attribute *attr, const char *buf, size_t size) \
183 	{ \
184 		return ledtrig_tty_attr_store(dev, buf, size, trigger); \
185 	} \
186 	static DEVICE_ATTR_RW(trigger_name)
187 
188 DEFINE_TTY_TRIGGER(rx, TRIGGER_TTY_RX);
189 DEFINE_TTY_TRIGGER(tx, TRIGGER_TTY_TX);
190 DEFINE_TTY_TRIGGER(cts, TRIGGER_TTY_CTS);
191 DEFINE_TTY_TRIGGER(dsr, TRIGGER_TTY_DSR);
192 DEFINE_TTY_TRIGGER(dcd, TRIGGER_TTY_DCD);
193 DEFINE_TTY_TRIGGER(rng, TRIGGER_TTY_RNG);
194 
195 static void ledtrig_tty_work(struct work_struct *work)
196 {
197 	struct ledtrig_tty_data *trigger_data =
198 		container_of(work, struct ledtrig_tty_data, dwork.work);
199 	enum led_trigger_tty_state state = TTY_LED_DISABLE;
200 	unsigned long interval = LEDTRIG_TTY_INTERVAL;
201 	bool invert = false;
202 	int status;
203 	int ret;
204 
205 	if (!trigger_data->ttyname)
206 		goto out;
207 
208 	/* try to get the tty corresponding to $ttyname */
209 	if (!trigger_data->tty) {
210 		dev_t devno;
211 		struct tty_struct *tty;
212 		int ret;
213 
214 		ret = tty_dev_name_to_number(trigger_data->ttyname, &devno);
215 		if (ret < 0)
216 			/*
217 			 * A device with this name might appear later, so keep
218 			 * retrying.
219 			 */
220 			goto out;
221 
222 		tty = tty_kopen_shared(devno);
223 		if (IS_ERR(tty) || !tty)
224 			/* What to do? retry or abort */
225 			goto out;
226 
227 		trigger_data->tty = tty;
228 	}
229 
230 	status = tty_get_tiocm(trigger_data->tty);
231 	if (status > 0) {
232 		if (trigger_data->mode_cts) {
233 			if (status & TIOCM_CTS)
234 				state = TTY_LED_ENABLE;
235 		}
236 
237 		if (trigger_data->mode_dsr) {
238 			if (status & TIOCM_DSR)
239 				state = TTY_LED_ENABLE;
240 		}
241 
242 		if (trigger_data->mode_dcd) {
243 			if (status & TIOCM_CAR)
244 				state = TTY_LED_ENABLE;
245 		}
246 
247 		if (trigger_data->mode_rng) {
248 			if (status & TIOCM_RNG)
249 				state = TTY_LED_ENABLE;
250 		}
251 	}
252 
253 	/*
254 	 * The evaluation of rx/tx must be done after the evaluation
255 	 * of TIOCM_*, because rx/tx has priority.
256 	 */
257 	if (trigger_data->mode_rx || trigger_data->mode_tx) {
258 		struct serial_icounter_struct icount;
259 
260 		ret = tty_get_icount(trigger_data->tty, &icount);
261 		if (ret)
262 			goto out;
263 
264 		if (trigger_data->mode_tx && (icount.tx != trigger_data->tx)) {
265 			trigger_data->tx = icount.tx;
266 			invert = state == TTY_LED_ENABLE;
267 			state = TTY_LED_BLINK;
268 		}
269 
270 		if (trigger_data->mode_rx && (icount.rx != trigger_data->rx)) {
271 			trigger_data->rx = icount.rx;
272 			invert = state == TTY_LED_ENABLE;
273 			state = TTY_LED_BLINK;
274 		}
275 	}
276 
277 out:
278 	switch (state) {
279 	case TTY_LED_BLINK:
280 		led_blink_set_oneshot(trigger_data->led_cdev, &interval,
281 				&interval, invert);
282 		break;
283 	case TTY_LED_ENABLE:
284 		led_set_brightness(trigger_data->led_cdev,
285 				trigger_data->led_cdev->blink_brightness);
286 		break;
287 	case TTY_LED_DISABLE:
288 		fallthrough;
289 	default:
290 		led_set_brightness(trigger_data->led_cdev, LED_OFF);
291 		break;
292 	}
293 
294 	complete_all(&trigger_data->sysfs);
295 	schedule_delayed_work(&trigger_data->dwork,
296 			      msecs_to_jiffies(LEDTRIG_TTY_INTERVAL * 2));
297 }
298 
299 static struct attribute *ledtrig_tty_attrs[] = {
300 	&dev_attr_ttyname.attr,
301 	&dev_attr_rx.attr,
302 	&dev_attr_tx.attr,
303 	&dev_attr_cts.attr,
304 	&dev_attr_dsr.attr,
305 	&dev_attr_dcd.attr,
306 	&dev_attr_rng.attr,
307 	NULL
308 };
309 ATTRIBUTE_GROUPS(ledtrig_tty);
310 
311 static int ledtrig_tty_activate(struct led_classdev *led_cdev)
312 {
313 	struct ledtrig_tty_data *trigger_data;
314 
315 	trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
316 	if (!trigger_data)
317 		return -ENOMEM;
318 
319 	/* Enable default rx/tx mode */
320 	trigger_data->mode_rx = true;
321 	trigger_data->mode_tx = true;
322 
323 	led_set_trigger_data(led_cdev, trigger_data);
324 
325 	INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
326 	trigger_data->led_cdev = led_cdev;
327 	init_completion(&trigger_data->sysfs);
328 
329 	schedule_delayed_work(&trigger_data->dwork, 0);
330 
331 	return 0;
332 }
333 
334 static void ledtrig_tty_deactivate(struct led_classdev *led_cdev)
335 {
336 	struct ledtrig_tty_data *trigger_data = led_get_trigger_data(led_cdev);
337 
338 	cancel_delayed_work_sync(&trigger_data->dwork);
339 
340 	kfree(trigger_data->ttyname);
341 	tty_kref_put(trigger_data->tty);
342 	trigger_data->tty = NULL;
343 
344 	kfree(trigger_data);
345 }
346 
347 static struct led_trigger ledtrig_tty = {
348 	.name = "tty",
349 	.activate = ledtrig_tty_activate,
350 	.deactivate = ledtrig_tty_deactivate,
351 	.groups = ledtrig_tty_groups,
352 };
353 module_led_trigger(ledtrig_tty);
354 
355 MODULE_AUTHOR("Uwe Kleine-König <u.kleine-koenig@pengutronix.de>");
356 MODULE_DESCRIPTION("UART LED trigger");
357 MODULE_LICENSE("GPL v2");
358