gpio-mockup.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * GPIO Testing Device Driver
  4 *
  5 * Copyright (C) 2014  Kamlakant Patel <kamlakant.patel@broadcom.com>
  6 * Copyright (C) 2015-2016  Bamvor Jian Zhang <bamv2005@gmail.com>
  7 * Copyright (C) 2017 Bartosz Golaszewski <brgl@bgdev.pl>
  8 */
  9
 10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 11
 12#include <linux/cleanup.h>
 13#include <linux/debugfs.h>
 14#include <linux/device.h>
 15#include <linux/gpio/driver.h>
 16#include <linux/interrupt.h>
 17#include <linux/irq.h>
 18#include <linux/irq_sim.h>
 19#include <linux/irqdomain.h>
 20#include <linux/mod_devicetable.h>
 21#include <linux/module.h>
 22#include <linux/platform_device.h>
 23#include <linux/property.h>
 24#include <linux/seq_file.h>
 25#include <linux/slab.h>
 26#include <linux/string_helpers.h>
 27#include <linux/uaccess.h>
 28
 29#define GPIO_MOCKUP_MAX_GC	10
 30/*
 31 * We're storing two values per chip: the GPIO base and the number
 32 * of GPIO lines.
 33 */
 34#define GPIO_MOCKUP_MAX_RANGES	(GPIO_MOCKUP_MAX_GC * 2)
 35/* Maximum of four properties + the sentinel. */
 36#define GPIO_MOCKUP_MAX_PROP	5
 37
 38/*
 39 * struct gpio_pin_status - structure describing a GPIO status
 40 * @dir:       Configures direction of gpio as "in" or "out"
 41 * @value:     Configures status of the gpio as 0(low) or 1(high)
 42 * @pull:      Configures the current pull of the GPIO as 0 (pull-down) or
 43 *             1 (pull-up)
 44 * @requested: Request status of this GPIO
 45 */
 46struct gpio_mockup_line_status {
 47	int dir;
 48	int value;
 49	int pull;
 50	bool requested;
 51};
 52
 53struct gpio_mockup_chip {
 54	struct gpio_chip gc;
 55	struct gpio_mockup_line_status *lines;
 56	struct irq_domain *irq_sim_domain;
 57	struct dentry *dbg_dir;
 58	struct mutex lock;
 59};
 60
 61struct gpio_mockup_dbgfs_private {
 62	struct gpio_mockup_chip *chip;
 63	unsigned int offset;
 64};
 65
 66static int gpio_mockup_ranges[GPIO_MOCKUP_MAX_RANGES];
 67static int gpio_mockup_num_ranges;
 68module_param_array(gpio_mockup_ranges, int, &gpio_mockup_num_ranges, 0400);
 69
 70static bool gpio_mockup_named_lines;
 71module_param_named(gpio_mockup_named_lines,
 72		   gpio_mockup_named_lines, bool, 0400);
 73
 74static struct dentry *gpio_mockup_dbg_dir;
 75
 76static int gpio_mockup_range_base(unsigned int index)
 77{
 78	return gpio_mockup_ranges[index * 2];
 79}
 80
 81static int gpio_mockup_range_ngpio(unsigned int index)
 82{
 83	return gpio_mockup_ranges[index * 2 + 1];
 84}
 85
 86static int __gpio_mockup_get(struct gpio_mockup_chip *chip,
 87			     unsigned int offset)
 88{
 89	return chip->lines[offset].value;
 90}
 91
 92static int gpio_mockup_get(struct gpio_chip *gc, unsigned int offset)
 93{
 94	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
 95	int val;
 96
 97	scoped_guard(mutex, &chip->lock)
 98		val = __gpio_mockup_get(chip, offset);
 99
100	return val;
101}
102
103static int gpio_mockup_get_multiple(struct gpio_chip *gc,
104				    unsigned long *mask, unsigned long *bits)
105{
106	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
107	unsigned int bit, val;
108
109	scoped_guard(mutex, &chip->lock) {
110		for_each_set_bit(bit, mask, gc->ngpio) {
111			val = __gpio_mockup_get(chip, bit);
112			__assign_bit(bit, bits, val);
113		}
114	}
115
116	return 0;
117}
118
119static void __gpio_mockup_set(struct gpio_mockup_chip *chip,
120			      unsigned int offset, int value)
121{
122	chip->lines[offset].value = !!value;
123}
124
125static int gpio_mockup_set(struct gpio_chip *gc,
126			   unsigned int offset, int value)
127{
128	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
129
130	guard(mutex)(&chip->lock);
131
132	__gpio_mockup_set(chip, offset, value);
133
134	return 0;
135}
136
137static int gpio_mockup_set_multiple(struct gpio_chip *gc,
138				    unsigned long *mask, unsigned long *bits)
139{
140	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
141	unsigned int bit;
142
143	guard(mutex)(&chip->lock);
144
145	for_each_set_bit(bit, mask, gc->ngpio)
146		__gpio_mockup_set(chip, bit, test_bit(bit, bits));
147
148	return 0;
149}
150
151static int gpio_mockup_apply_pull(struct gpio_mockup_chip *chip,
152				  unsigned int offset, int value)
153{
154	struct gpio_mockup_line_status *line = &chip->lines[offset];
155	int curr, irq, irq_type, ret = 0;
156
157	guard(mutex)(&chip->lock);
158
159	if (line->requested && line->dir == GPIO_LINE_DIRECTION_IN) {
160		curr = __gpio_mockup_get(chip, offset);
161		if (curr == value)
162			goto out;
163
164		irq = irq_find_mapping(chip->irq_sim_domain, offset);
165		if (!irq)
166			/*
167			 * This is fine - it just means, nobody is listening
168			 * for interrupts on this line, otherwise
169			 * irq_create_mapping() would have been called from
170			 * the to_irq() callback.
171			 */
172			goto set_value;
173
174		irq_type = irq_get_trigger_type(irq);
175
176		if ((value == 1 && (irq_type & IRQ_TYPE_EDGE_RISING)) ||
177		    (value == 0 && (irq_type & IRQ_TYPE_EDGE_FALLING))) {
178			ret = irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING,
179						    true);
180			if (ret)
181				goto out;
182		}
183	}
184
185set_value:
186	/* Change the value unless we're actively driving the line. */
187	if (!line->requested || line->dir == GPIO_LINE_DIRECTION_IN)
188		__gpio_mockup_set(chip, offset, value);
189
190out:
191	chip->lines[offset].pull = value;
192	return ret;
193}
194
195static int gpio_mockup_set_config(struct gpio_chip *gc,
196				  unsigned int offset, unsigned long config)
197{
198	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
199
200	switch (pinconf_to_config_param(config)) {
201	case PIN_CONFIG_BIAS_PULL_UP:
202		return gpio_mockup_apply_pull(chip, offset, 1);
203	case PIN_CONFIG_BIAS_PULL_DOWN:
204		return gpio_mockup_apply_pull(chip, offset, 0);
205	default:
206		break;
207	}
208	return -ENOTSUPP;
209}
210
211static int gpio_mockup_dirout(struct gpio_chip *gc,
212			      unsigned int offset, int value)
213{
214	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
215
216	scoped_guard(mutex, &chip->lock) {
217		chip->lines[offset].dir = GPIO_LINE_DIRECTION_OUT;
218		__gpio_mockup_set(chip, offset, value);
219	}
220
221	return 0;
222}
223
224static int gpio_mockup_dirin(struct gpio_chip *gc, unsigned int offset)
225{
226	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
227
228	scoped_guard(mutex, &chip->lock)
229		chip->lines[offset].dir = GPIO_LINE_DIRECTION_IN;
230
231	return 0;
232}
233
234static int gpio_mockup_get_direction(struct gpio_chip *gc, unsigned int offset)
235{
236	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
237	int direction;
238
239	scoped_guard(mutex, &chip->lock)
240		direction = chip->lines[offset].dir;
241
242	return direction;
243}
244
245static int gpio_mockup_to_irq(struct gpio_chip *gc, unsigned int offset)
246{
247	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
248
249	return irq_create_mapping(chip->irq_sim_domain, offset);
250}
251
252static int gpio_mockup_request(struct gpio_chip *gc, unsigned int offset)
253{
254	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
255
256	scoped_guard(mutex, &chip->lock)
257		chip->lines[offset].requested = true;
258
259	return 0;
260}
261
262static void gpio_mockup_free(struct gpio_chip *gc, unsigned int offset)
263{
264	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
265
266	guard(mutex)(&chip->lock);
267
268	chip->lines[offset].requested = false;
269	__gpio_mockup_set(chip, offset, chip->lines[offset].pull);
270}
271
272static ssize_t gpio_mockup_debugfs_read(struct file *file,
273					char __user *usr_buf,
274					size_t size, loff_t *ppos)
275{
276	struct gpio_mockup_dbgfs_private *priv;
277	struct gpio_mockup_chip *chip;
278	struct seq_file *sfile;
279	struct gpio_chip *gc;
280	int val, cnt;
281	char buf[3];
282
283	if (*ppos != 0)
284		return 0;
285
286	sfile = file->private_data;
287	priv = sfile->private;
288	chip = priv->chip;
289	gc = &chip->gc;
290
291	val = gpio_mockup_get(gc, priv->offset);
292	cnt = snprintf(buf, sizeof(buf), "%d\n", val);
293
294	return simple_read_from_buffer(usr_buf, size, ppos, buf, cnt);
295}
296
297static ssize_t gpio_mockup_debugfs_write(struct file *file,
298					 const char __user *usr_buf,
299					 size_t size, loff_t *ppos)
300{
301	struct gpio_mockup_dbgfs_private *priv;
302	int rv, val;
303	struct seq_file *sfile;
304
305	if (*ppos != 0)
306		return -EINVAL;
307
308	rv = kstrtoint_from_user(usr_buf, size, 0, &val);
309	if (rv)
310		return rv;
311	if (val != 0 && val != 1)
312		return -EINVAL;
313
314	sfile = file->private_data;
315	priv = sfile->private;
316	rv = gpio_mockup_apply_pull(priv->chip, priv->offset, val);
317	if (rv)
318		return rv;
319
320	return size;
321}
322
323static int gpio_mockup_debugfs_open(struct inode *inode, struct file *file)
324{
325	return single_open(file, NULL, inode->i_private);
326}
327
328/*
329 * Each mockup chip is represented by a directory named after the chip's device
330 * name under /sys/kernel/debug/gpio-mockup/. Each line is represented by
331 * a file using the line's offset as the name under the chip's directory.
332 *
333 * Reading from the line's file yields the current *value*, writing to the
334 * line's file changes the current *pull*. Default pull for mockup lines is
335 * down.
336 *
337 * Examples:
338 * - when a line pulled down is requested in output mode and driven high, its
339 *   value will return to 0 once it's released
340 * - when the line is requested in output mode and driven high, writing 0 to
341 *   the corresponding debugfs file will change the pull to down but the
342 *   reported value will still be 1 until the line is released
343 * - line requested in input mode always reports the same value as its pull
344 *   configuration
345 * - when the line is requested in input mode and monitored for events, writing
346 *   the same value to the debugfs file will be a noop, while writing the
347 *   opposite value will generate a dummy interrupt with an appropriate edge
348 */
349static const struct file_operations gpio_mockup_debugfs_ops = {
350	.owner = THIS_MODULE,
351	.open = gpio_mockup_debugfs_open,
352	.read = gpio_mockup_debugfs_read,
353	.write = gpio_mockup_debugfs_write,
354	.release = single_release,
355};
356
357static void gpio_mockup_debugfs_setup(struct device *dev,
358				      struct gpio_mockup_chip *chip)
359{
360	struct gpio_mockup_dbgfs_private *priv;
361	struct gpio_chip *gc;
362	const char *devname;
363	char *name;
364	int i;
365
366	gc = &chip->gc;
367
368	/*
369	 * There can only be a single GPIO device per platform device in
370	 * gpio-mockup so using device_find_any_child() is OK.
371	 */
372	struct device *child __free(put_device) = device_find_any_child(dev);
373	if (!child)
374		return;
375
376	devname = dev_name(child);
377	chip->dbg_dir = debugfs_create_dir(devname, gpio_mockup_dbg_dir);
378
379	for (i = 0; i < gc->ngpio; i++) {
380		name = devm_kasprintf(dev, GFP_KERNEL, "%d", i);
381		if (!name)
382			return;
383
384		priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
385		if (!priv)
386			return;
387
388		priv->chip = chip;
389		priv->offset = i;
390
391		debugfs_create_file(name, 0600, chip->dbg_dir, priv,
392				    &gpio_mockup_debugfs_ops);
393	}
394}
395
396static void gpio_mockup_debugfs_cleanup(void *data)
397{
398	struct gpio_mockup_chip *chip = data;
399
400	debugfs_remove_recursive(chip->dbg_dir);
401}
402
403static void gpio_mockup_dispose_mappings(void *data)
404{
405	struct gpio_mockup_chip *chip = data;
406	struct gpio_chip *gc = &chip->gc;
407	int i, irq;
408
409	for (i = 0; i < gc->ngpio; i++) {
410		irq = irq_find_mapping(chip->irq_sim_domain, i);
411		if (irq)
412			irq_dispose_mapping(irq);
413	}
414}
415
416static int gpio_mockup_probe(struct platform_device *pdev)
417{
418	struct gpio_mockup_chip *chip;
419	struct gpio_chip *gc;
420	struct device *dev;
421	const char *name;
422	int rv, base, i;
423	u16 ngpio;
424
425	dev = &pdev->dev;
426
427	rv = device_property_read_u32(dev, "gpio-base", &base);
428	if (rv)
429		base = -1;
430
431	rv = device_property_read_u16(dev, "nr-gpios", &ngpio);
432	if (rv)
433		return rv;
434
435	rv = device_property_read_string(dev, "chip-label", &name);
436	if (rv)
437		name = dev_name(dev);
438
439	chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
440	if (!chip)
441		return -ENOMEM;
442
443	mutex_init(&chip->lock);
444
445	gc = &chip->gc;
446	gc->base = base;
447	gc->ngpio = ngpio;
448	gc->label = name;
449	gc->owner = THIS_MODULE;
450	gc->parent = dev;
451	gc->get = gpio_mockup_get;
452	gc->set = gpio_mockup_set;
453	gc->get_multiple = gpio_mockup_get_multiple;
454	gc->set_multiple = gpio_mockup_set_multiple;
455	gc->direction_output = gpio_mockup_dirout;
456	gc->direction_input = gpio_mockup_dirin;
457	gc->get_direction = gpio_mockup_get_direction;
458	gc->set_config = gpio_mockup_set_config;
459	gc->to_irq = gpio_mockup_to_irq;
460	gc->request = gpio_mockup_request;
461	gc->free = gpio_mockup_free;
462
463	chip->lines = devm_kcalloc(dev, gc->ngpio,
464				   sizeof(*chip->lines), GFP_KERNEL);
465	if (!chip->lines)
466		return -ENOMEM;
467
468	for (i = 0; i < gc->ngpio; i++)
469		chip->lines[i].dir = GPIO_LINE_DIRECTION_IN;
470
471	chip->irq_sim_domain = devm_irq_domain_create_sim(dev, NULL,
472							  gc->ngpio);
473	if (IS_ERR(chip->irq_sim_domain))
474		return PTR_ERR(chip->irq_sim_domain);
475
476	rv = devm_add_action_or_reset(dev, gpio_mockup_dispose_mappings, chip);
477	if (rv)
478		return rv;
479
480	rv = devm_gpiochip_add_data(dev, &chip->gc, chip);
481	if (rv)
482		return rv;
483
484	gpio_mockup_debugfs_setup(dev, chip);
485
486	return devm_add_action_or_reset(dev, gpio_mockup_debugfs_cleanup, chip);
487}
488
489static const struct of_device_id gpio_mockup_of_match[] = {
490	{ .compatible = "gpio-mockup", },
491	{},
492};
493MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
494
495static struct platform_driver gpio_mockup_driver = {
496	.driver = {
497		.name = "gpio-mockup",
498		.of_match_table = gpio_mockup_of_match,
499	},
500	.probe = gpio_mockup_probe,
501};
502
503static struct platform_device *gpio_mockup_pdevs[GPIO_MOCKUP_MAX_GC];
504
505static void gpio_mockup_unregister_pdevs(void)
506{
507	struct platform_device *pdev;
508	struct fwnode_handle *fwnode;
509	int i;
510
511	for (i = 0; i < GPIO_MOCKUP_MAX_GC; i++) {
512		pdev = gpio_mockup_pdevs[i];
513		if (!pdev)
514			continue;
515
516		fwnode = dev_fwnode(&pdev->dev);
517		platform_device_unregister(pdev);
518		fwnode_remove_software_node(fwnode);
519	}
520}
521
522static int __init gpio_mockup_register_chip(int idx)
523{
524	struct property_entry properties[GPIO_MOCKUP_MAX_PROP];
525	struct platform_device_info pdevinfo;
526	struct platform_device *pdev;
527	struct fwnode_handle *fwnode;
528	char **line_names = NULL;
529	char chip_label[32];
530	int prop = 0, base;
531	u16 ngpio;
532
533	memset(properties, 0, sizeof(properties));
534	memset(&pdevinfo, 0, sizeof(pdevinfo));
535
536	snprintf(chip_label, sizeof(chip_label), "gpio-mockup-%c", idx + 'A');
537	properties[prop++] = PROPERTY_ENTRY_STRING("chip-label", chip_label);
538
539	base = gpio_mockup_range_base(idx);
540	if (base >= 0)
541		properties[prop++] = PROPERTY_ENTRY_U32("gpio-base", base);
542
543	ngpio = base < 0 ? gpio_mockup_range_ngpio(idx)
544			 : gpio_mockup_range_ngpio(idx) - base;
545	properties[prop++] = PROPERTY_ENTRY_U16("nr-gpios", ngpio);
546
547	if (gpio_mockup_named_lines) {
548		line_names = kasprintf_strarray(GFP_KERNEL, chip_label, ngpio);
549		if (!line_names)
550			return -ENOMEM;
551
552		properties[prop++] = PROPERTY_ENTRY_STRING_ARRAY_LEN(
553					"gpio-line-names", line_names, ngpio);
554	}
555
556	fwnode = fwnode_create_software_node(properties, NULL);
557	if (IS_ERR(fwnode)) {
558		kfree_strarray(line_names, ngpio);
559		return PTR_ERR(fwnode);
560	}
561
562	pdevinfo.name = "gpio-mockup";
563	pdevinfo.id = idx;
564	pdevinfo.fwnode = fwnode;
565
566	pdev = platform_device_register_full(&pdevinfo);
567	kfree_strarray(line_names, ngpio);
568	if (IS_ERR(pdev)) {
569		fwnode_remove_software_node(fwnode);
570		pr_err("error registering device");
571		return PTR_ERR(pdev);
572	}
573
574	gpio_mockup_pdevs[idx] = pdev;
575
576	return 0;
577}
578
579static int __init gpio_mockup_init(void)
580{
581	int i, num_chips, err;
582
583	if ((gpio_mockup_num_ranges % 2) ||
584	    (gpio_mockup_num_ranges > GPIO_MOCKUP_MAX_RANGES))
585		return -EINVAL;
586
587	/* Each chip is described by two values. */
588	num_chips = gpio_mockup_num_ranges / 2;
589
590	/*
591	 * The second value in the <base GPIO - number of GPIOS> pair must
592	 * always be greater than 0.
593	 */
594	for (i = 0; i < num_chips; i++) {
595		if (gpio_mockup_range_ngpio(i) < 0)
596			return -EINVAL;
597	}
598
599	gpio_mockup_dbg_dir = debugfs_create_dir("gpio-mockup", NULL);
600
601	err = platform_driver_register(&gpio_mockup_driver);
602	if (err) {
603		pr_err("error registering platform driver\n");
604		debugfs_remove_recursive(gpio_mockup_dbg_dir);
605		return err;
606	}
607
608	for (i = 0; i < num_chips; i++) {
609		err = gpio_mockup_register_chip(i);
610		if (err) {
611			platform_driver_unregister(&gpio_mockup_driver);
612			gpio_mockup_unregister_pdevs();
613			debugfs_remove_recursive(gpio_mockup_dbg_dir);
614			return err;
615		}
616	}
617
618	return 0;
619}
620
621static void __exit gpio_mockup_exit(void)
622{
623	gpio_mockup_unregister_pdevs();
624	debugfs_remove_recursive(gpio_mockup_dbg_dir);
625	platform_driver_unregister(&gpio_mockup_driver);
626}
627
628module_init(gpio_mockup_init);
629module_exit(gpio_mockup_exit);
630
631MODULE_AUTHOR("Kamlakant Patel <kamlakant.patel@broadcom.com>");
632MODULE_AUTHOR("Bamvor Jian Zhang <bamv2005@gmail.com>");
633MODULE_AUTHOR("Bartosz Golaszewski <brgl@bgdev.pl>");
634MODULE_DESCRIPTION("GPIO Testing driver");
635MODULE_LICENSE("GPL v2");