4  * Copyright (c) 2017 Andreas Klinger <ak@it-klinger.de>
17  * http://www.robot-electronics.co.uk/htm/srf04tech.htm
21  *          +---+
23  * trig:  --+   +------------------------------------------------------
25  *          |<->|
28  * ultra           +-+ +-+ +-+
30  * burst: ---------+ +-+ +-+ +-----------------------------------------
32  * ultra                     .              +-+ +-+ +-+
34  * echo:  ----------------------------------+ +-+ +-+ +----------------
36  *                           +------------------------+
38  * echo:  -------------------+                        +---------------
42  *                           |<---------------------->|
44  *                              --> one round trip of ultra sonic waves
77 	if (gpiod_get_value(data->gpiod_echo)) {  in srf04_handle_irq()
78 		data->ts_rising = now;  in srf04_handle_irq()
79 		complete(&data->rising);  in srf04_handle_irq()
81 		data->ts_falling = now;  in srf04_handle_irq()
82 		complete(&data->falling);  in srf04_handle_irq()
96 	 * just one read-echo-cycle can take place at a time  in srf04_read()
99 	mutex_lock(&data->lock);  in srf04_read()
101 	reinit_completion(&data->rising);  in srf04_read()
102 	reinit_completion(&data->falling);  in srf04_read()
104 	gpiod_set_value(data->gpiod_trig, 1);  in srf04_read()
106 	gpiod_set_value(data->gpiod_trig, 0);  in srf04_read()
109 	ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);  in srf04_read()
111 		mutex_unlock(&data->lock);  in srf04_read()
114 		mutex_unlock(&data->lock);  in srf04_read()
115 		return -ETIMEDOUT;  in srf04_read()
119 	ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);  in srf04_read()
121 		mutex_unlock(&data->lock);  in srf04_read()
124 		mutex_unlock(&data->lock);  in srf04_read()
125 		return -ETIMEDOUT;  in srf04_read()
128 	ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);  in srf04_read()
130 	mutex_unlock(&data->lock);  in srf04_read()
141 	 * time = ---------- = ------------ = 40438871 ns  in srf04_read()
144 	 * using a minimum speed at -20 °C of 319 m/s  in srf04_read()
147 		return -EIO;  in srf04_read()
163 	 * distance = ------ * ------- = ------------  in srf04_read()
183 	if (channel->type != IIO_DISTANCE)  in srf04_read_raw()
184 		return -EINVAL;  in srf04_read_raw()
202 		return -EINVAL;  in srf04_read_raw()
221 	struct device *dev = &pdev->dev;  in srf04_probe()
229 		return -ENOMEM;  in srf04_probe()
233 	data->dev = dev;  in srf04_probe()
235 	mutex_init(&data->lock);  in srf04_probe()
236 	init_completion(&data->rising);  in srf04_probe()
237 	init_completion(&data->falling);  in srf04_probe()
239 	data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);  in srf04_probe()
240 	if (IS_ERR(data->gpiod_trig)) {  in srf04_probe()
241 		dev_err(dev, "failed to get trig-gpios: err=%ld\n",  in srf04_probe()
242 					PTR_ERR(data->gpiod_trig));  in srf04_probe()
243 		return PTR_ERR(data->gpiod_trig);  in srf04_probe()
246 	data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);  in srf04_probe()
247 	if (IS_ERR(data->gpiod_echo)) {  in srf04_probe()
248 		dev_err(dev, "failed to get echo-gpios: err=%ld\n",  in srf04_probe()
249 					PTR_ERR(data->gpiod_echo));  in srf04_probe()
250 		return PTR_ERR(data->gpiod_echo);  in srf04_probe()
253 	if (gpiod_cansleep(data->gpiod_echo)) {  in srf04_probe()
254 		dev_err(data->dev, "cansleep-GPIOs not supported\n");  in srf04_probe()
255 		return -ENODEV;  in srf04_probe()
258 	data->irqnr = gpiod_to_irq(data->gpiod_echo);  in srf04_probe()
259 	if (data->irqnr < 0) {  in srf04_probe()
260 		dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);  in srf04_probe()
261 		return data->irqnr;  in srf04_probe()
264 	ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,  in srf04_probe()
266 			pdev->name, indio_dev);  in srf04_probe()
268 		dev_err(data->dev, "request_irq: %d\n", ret);  in srf04_probe()
274 	indio_dev->name = "srf04";  in srf04_probe()
275 	indio_dev->dev.parent = &pdev->dev;  in srf04_probe()
276 	indio_dev->info = &srf04_iio_info;  in srf04_probe()
277 	indio_dev->modes = INDIO_DIRECT_MODE;  in srf04_probe()
278 	indio_dev->channels = srf04_chan_spec;  in srf04_probe()
279 	indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);  in srf04_probe()
294 		.name		= "srf04-gpio",
301 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");