1/*
2 * Driver for pcf857x, pca857x, and pca967x I2C GPIO expanders
3 *
4 * Copyright (C) 2007 David Brownell
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 */
20
21#include <linux/kernel.h>
22#include <linux/slab.h>
23#include <linux/gpio.h>
24#include <linux/i2c.h>
25#include <linux/i2c/pcf857x.h>
26#include <linux/module.h>
27
28
29static const struct i2c_device_id pcf857x_id[] = {
30	{ "pcf8574", 8 },
31	{ "pcf8574a", 8 },
32	{ "pca8574", 8 },
33	{ "pca9670", 8 },
34	{ "pca9672", 8 },
35	{ "pca9674", 8 },
36	{ "pcf8575", 16 },
37	{ "pca8575", 16 },
38	{ "pca9671", 16 },
39	{ "pca9673", 16 },
40	{ "pca9675", 16 },
41	{ "max7328", 8 },
42	{ "max7329", 8 },
43	{ }
44};
45MODULE_DEVICE_TABLE(i2c, pcf857x_id);
46
47/*
48 * The pcf857x, pca857x, and pca967x chips only expose one read and one
49 * write register.  Writing a "one" bit (to match the reset state) lets
50 * that pin be used as an input; it's not an open-drain model, but acts
51 * a bit like one.  This is described as "quasi-bidirectional"; read the
52 * chip documentation for details.
53 *
54 * Many other I2C GPIO expander chips (like the pca953x models) have
55 * more complex register models and more conventional circuitry using
56 * push/pull drivers.  They often use the same 0x20..0x27 addresses as
57 * pcf857x parts, making the "legacy" I2C driver model problematic.
58 */
59struct pcf857x {
60	struct gpio_chip	chip;
61	struct i2c_client	*client;
62	struct mutex		lock;		/* protect 'out' */
63	unsigned		out;		/* software latch */
64};
65
66/*-------------------------------------------------------------------------*/
67
68/* Talk to 8-bit I/O expander */
69
70static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
71{
72	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
73	int		status;
74
75	mutex_lock(&gpio->lock);
76	gpio->out |= (1 << offset);
77	status = i2c_smbus_write_byte(gpio->client, gpio->out);
78	mutex_unlock(&gpio->lock);
79
80	return status;
81}
82
83static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
84{
85	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
86	s32		value;
87
88	value = i2c_smbus_read_byte(gpio->client);
89	return (value < 0) ? 0 : (value & (1 << offset));
90}
91
92static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
93{
94	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
95	unsigned	bit = 1 << offset;
96	int		status;
97
98	mutex_lock(&gpio->lock);
99	if (value)
100		gpio->out |= bit;
101	else
102		gpio->out &= ~bit;
103	status = i2c_smbus_write_byte(gpio->client, gpio->out);
104	mutex_unlock(&gpio->lock);
105
106	return status;
107}
108
109static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
110{
111	pcf857x_output8(chip, offset, value);
112}
113
114/*-------------------------------------------------------------------------*/
115
116/* Talk to 16-bit I/O expander */
117
118static int i2c_write_le16(struct i2c_client *client, u16 word)
119{
120	u8 buf[2] = { word & 0xff, word >> 8, };
121	int status;
122
123	status = i2c_master_send(client, buf, 2);
124	return (status < 0) ? status : 0;
125}
126
127static int i2c_read_le16(struct i2c_client *client)
128{
129	u8 buf[2];
130	int status;
131
132	status = i2c_master_recv(client, buf, 2);
133	if (status < 0)
134		return status;
135	return (buf[1] << 8) | buf[0];
136}
137
138static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
139{
140	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
141	int		status;
142
143	mutex_lock(&gpio->lock);
144	gpio->out |= (1 << offset);
145	status = i2c_write_le16(gpio->client, gpio->out);
146	mutex_unlock(&gpio->lock);
147
148	return status;
149}
150
151static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
152{
153	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
154	int		value;
155
156	value = i2c_read_le16(gpio->client);
157	return (value < 0) ? 0 : (value & (1 << offset));
158}
159
160static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
161{
162	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
163	unsigned	bit = 1 << offset;
164	int		status;
165
166	mutex_lock(&gpio->lock);
167	if (value)
168		gpio->out |= bit;
169	else
170		gpio->out &= ~bit;
171	status = i2c_write_le16(gpio->client, gpio->out);
172	mutex_unlock(&gpio->lock);
173
174	return status;
175}
176
177static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
178{
179	pcf857x_output16(chip, offset, value);
180}
181
182/*-------------------------------------------------------------------------*/
183
184static int pcf857x_probe(struct i2c_client *client,
185			 const struct i2c_device_id *id)
186{
187	struct pcf857x_platform_data	*pdata;
188	struct pcf857x			*gpio;
189	int				status;
190
191	pdata = client->dev.platform_data;
192	if (!pdata) {
193		dev_dbg(&client->dev, "no platform data\n");
194	}
195
196	/* Allocate, initialize, and register this gpio_chip. */
197	gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
198	if (!gpio)
199		return -ENOMEM;
200
201	mutex_init(&gpio->lock);
202
203	gpio->chip.base = pdata ? pdata->gpio_base : -1;
204	gpio->chip.can_sleep = 1;
205	gpio->chip.dev = &client->dev;
206	gpio->chip.owner = THIS_MODULE;
207
208	/* NOTE:  the OnSemi jlc1562b is also largely compatible with
209	 * these parts, notably for output.  It has a low-resolution
210	 * DAC instead of pin change IRQs; and its inputs can be the
211	 * result of comparators.
212	 */
213
214	/* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
215	 * 9670, 9672, 9764, and 9764a use quite a variety.
216	 *
217	 * NOTE: we don't distinguish here between *4 and *4a parts.
218	 */
219	gpio->chip.ngpio = id->driver_data;
220	if (gpio->chip.ngpio == 8) {
221		gpio->chip.direction_input = pcf857x_input8;
222		gpio->chip.get = pcf857x_get8;
223		gpio->chip.direction_output = pcf857x_output8;
224		gpio->chip.set = pcf857x_set8;
225
226		if (!i2c_check_functionality(client->adapter,
227				I2C_FUNC_SMBUS_BYTE))
228			status = -EIO;
229
230		/* fail if there's no chip present */
231		else
232			status = i2c_smbus_read_byte(client);
233
234	/* '75/'75c addresses are 0x20..0x27, just like the '74;
235	 * the '75c doesn't have a current source pulling high.
236	 * 9671, 9673, and 9765 use quite a variety of addresses.
237	 *
238	 * NOTE: we don't distinguish here between '75 and '75c parts.
239	 */
240	} else if (gpio->chip.ngpio == 16) {
241		gpio->chip.direction_input = pcf857x_input16;
242		gpio->chip.get = pcf857x_get16;
243		gpio->chip.direction_output = pcf857x_output16;
244		gpio->chip.set = pcf857x_set16;
245
246		if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
247			status = -EIO;
248
249		/* fail if there's no chip present */
250		else
251			status = i2c_read_le16(client);
252
253	} else {
254		dev_dbg(&client->dev, "unsupported number of gpios\n");
255		status = -EINVAL;
256	}
257
258	if (status < 0)
259		goto fail;
260
261	gpio->chip.label = client->name;
262
263	gpio->client = client;
264	i2c_set_clientdata(client, gpio);
265
266	/* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
267	 * We can't actually know whether a pin is configured (a) as output
268	 * and driving the signal low, or (b) as input and reporting a low
269	 * value ... without knowing the last value written since the chip
270	 * came out of reset (if any).  We can't read the latched output.
271	 *
272	 * In short, the only reliable solution for setting up pin direction
273	 * is to do it explicitly.  The setup() method can do that, but it
274	 * may cause transient glitching since it can't know the last value
275	 * written (some pins may need to be driven low).
276	 *
277	 * Using pdata->n_latch avoids that trouble.  When left initialized
278	 * to zero, our software copy of the "latch" then matches the chip's
279	 * all-ones reset state.  Otherwise it flags pins to be driven low.
280	 */
281	gpio->out = pdata ? ~pdata->n_latch : ~0;
282
283	status = gpiochip_add(&gpio->chip);
284	if (status < 0)
285		goto fail;
286
287	/* NOTE: these chips can issue "some pin-changed" IRQs, which we
288	 * don't yet even try to use.  Among other issues, the relevant
289	 * genirq state isn't available to modular drivers; and most irq
290	 * methods can't be called from sleeping contexts.
291	 */
292
293	dev_info(&client->dev, "%s\n",
294			client->irq ? " (irq ignored)" : "");
295
296	/* Let platform code set up the GPIOs and their users.
297	 * Now is the first time anyone could use them.
298	 */
299	if (pdata && pdata->setup) {
300		status = pdata->setup(client,
301				gpio->chip.base, gpio->chip.ngpio,
302				pdata->context);
303		if (status < 0)
304			dev_warn(&client->dev, "setup --> %d\n", status);
305	}
306
307	return 0;
308
309fail:
310	dev_dbg(&client->dev, "probe error %d for '%s'\n",
311			status, client->name);
312	kfree(gpio);
313	return status;
314}
315
316static int pcf857x_remove(struct i2c_client *client)
317{
318	struct pcf857x_platform_data	*pdata = client->dev.platform_data;
319	struct pcf857x			*gpio = i2c_get_clientdata(client);
320	int				status = 0;
321
322	if (pdata && pdata->teardown) {
323		status = pdata->teardown(client,
324				gpio->chip.base, gpio->chip.ngpio,
325				pdata->context);
326		if (status < 0) {
327			dev_err(&client->dev, "%s --> %d\n",
328					"teardown", status);
329			return status;
330		}
331	}
332
333	status = gpiochip_remove(&gpio->chip);
334	if (status == 0)
335		kfree(gpio);
336	else
337		dev_err(&client->dev, "%s --> %d\n", "remove", status);
338	return status;
339}
340
341static struct i2c_driver pcf857x_driver = {
342	.driver = {
343		.name	= "pcf857x",
344		.owner	= THIS_MODULE,
345	},
346	.probe	= pcf857x_probe,
347	.remove	= pcf857x_remove,
348	.id_table = pcf857x_id,
349};
350
351static int __init pcf857x_init(void)
352{
353	return i2c_add_driver(&pcf857x_driver);
354}
355/* register after i2c postcore initcall and before
356 * subsys initcalls that may rely on these GPIOs
357 */
358subsys_initcall(pcf857x_init);
359
360static void __exit pcf857x_exit(void)
361{
362	i2c_del_driver(&pcf857x_driver);
363}
364module_exit(pcf857x_exit);
365
366MODULE_LICENSE("GPL");
367MODULE_AUTHOR("David Brownell");
368