summaryrefslogtreecommitdiffstats
path: root/drivers/gpio/pcf857x.c
blob: 1106aa15ac79ad92d6807aab7a0aa2106e786784 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
/*
 * pcf857x - driver for pcf857x, pca857x, and pca967x I2C GPIO expanders
 *
 * Copyright (C) 2007 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/i2c/pcf857x.h>

#include <asm/gpio.h>


/*
 * The pcf857x, pca857x, and pca967x chips only expose one read and one
 * write register.  Writing a "one" bit (to match the reset state) lets
 * that pin be used as an input; it's not an open-drain model, but acts
 * a bit like one.  This is described as "quasi-bidirectional"; read the
 * chip documentation for details.
 *
 * Many other I2C GPIO expander chips (like the pca953x models) have
 * more complex register models and more conventional circuitry using
 * push/pull drivers.  They often use the same 0x20..0x27 addresses as
 * pcf857x parts, making the "legacy" I2C driver model problematic.
 */
struct pcf857x {
	struct gpio_chip	chip;
	struct i2c_client	*client;
	unsigned		out;		/* software latch */
};

/*-------------------------------------------------------------------------*/

/* Talk to 8-bit I/O expander */

static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
{
	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);

	gpio->out |= (1 << offset);
	return i2c_smbus_write_byte(gpio->client, gpio->out);
}

static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
{
	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
	s32		value;

	value = i2c_smbus_read_byte(gpio->client);
	return (value < 0) ? 0 : (value & (1 << offset));
}

static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
{
	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
	unsigned	bit = 1 << offset;

	if (value)
		gpio->out |= bit;
	else
		gpio->out &= ~bit;
	return i2c_smbus_write_byte(gpio->client, gpio->out);
}

static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
{
	pcf857x_output8(chip, offset, value);
}

/*-------------------------------------------------------------------------*/

/* Talk to 16-bit I/O expander */

static int i2c_write_le16(struct i2c_client *client, u16 word)
{
	u8 buf[2] = { word & 0xff, word >> 8, };
	int status;

	status = i2c_master_send(client, buf, 2);
	return (status < 0) ? status : 0;
}

static int i2c_read_le16(struct i2c_client *client)
{
	u8 buf[2];
	int status;

	status = i2c_master_recv(client, buf, 2);
	if (status < 0)
		return status;
	return (buf[1] << 8) | buf[0];
}

static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
{
	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);

	gpio->out |= (1 << offset);
	return i2c_write_le16(gpio->client, gpio->out);
}

static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
{
	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
	int		value;

	value = i2c_read_le16(gpio->client);
	return (value < 0) ? 0 : (value & (1 << offset));
}

static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
{
	struct pcf857x	*gpio = container_of(chip, struct pcf857x, chip);
	unsigned	bit = 1 << offset;

	if (value)
		gpio->out |= bit;
	else
		gpio->out &= ~bit;
	return i2c_write_le16(gpio->client, gpio->out);
}

static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
{
	pcf857x_output16(chip, offset, value);
}

/*-------------------------------------------------------------------------*/

static int pcf857x_probe(struct i2c_client *client)
{
	struct pcf857x_platform_data	*pdata;
	struct pcf857x			*gpio;
	int				status;

	pdata = client->dev.platform_data;
	if (!pdata)
		return -ENODEV;

	/* Allocate, initialize, and register this gpio_chip. */
	gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
	if (!gpio)
		return -ENOMEM;

	gpio->chip.base = pdata->gpio_base;
	gpio->chip.can_sleep = 1;
	gpio->chip.owner = THIS_MODULE;

	/* NOTE:  the OnSemi jlc1562b is also largely compatible with
	 * these parts, notably for output.  It has a low-resolution
	 * DAC instead of pin change IRQs; and its inputs can be the
	 * result of comparators.
	 */

	/* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
	 * 9670, 9672, 9764, and 9764a use quite a variety.
	 *
	 * NOTE: we don't distinguish here between *4 and *4a parts.
	 */
	if (strcmp(client->name, "pcf8574") == 0
			|| strcmp(client->name, "pca8574") == 0
			|| strcmp(client->name, "pca9670") == 0
			|| strcmp(client->name, "pca9672") == 0
			|| strcmp(client->name, "pca9674") == 0
			) {
		gpio->chip.ngpio = 8;
		gpio->chip.direction_input = pcf857x_input8;
		gpio->chip.get = pcf857x_get8;
		gpio->chip.direction_output = pcf857x_output8;
		gpio->chip.set = pcf857x_set8;

		if (!i2c_check_functionality(client->adapter,
				I2C_FUNC_SMBUS_BYTE))
			status = -EIO;

		/* fail if there's no chip present */
		else
			status = i2c_smbus_read_byte(client);

	/* '75/'75c addresses are 0x20..0x27, just like the '74;
	 * the '75c doesn't have a current source pulling high.
	 * 9671, 9673, and 9765 use quite a variety of addresses.
	 *
	 * NOTE: we don't distinguish here between '75 and '75c parts.
	 */
	} else if (strcmp(client->name, "pcf8575") == 0
			|| strcmp(client->name, "pca8575") == 0
			|| strcmp(client->name, "pca9671") == 0
			|| strcmp(client->name, "pca9673") == 0
			|| strcmp(client->name, "pca9675") == 0
			) {
		gpio->chip.ngpio = 16;
		gpio->chip.direction_input = pcf857x_input16;
		gpio->chip.get = pcf857x_get16;
		gpio->chip.direction_output = pcf857x_output16;
		gpio->chip.set = pcf857x_set16;

		if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
			status = -EIO;

		/* fail if there's no chip present */
		else
			status = i2c_read_le16(client);

	} else
		status = -ENODEV;

	if (status < 0)
		goto fail;

	gpio->chip.label = client->name;

	gpio->client = client;
	i2c_set_clientdata(client, gpio);

	/* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
	 * We can't actually know whether a pin is configured (a) as output
	 * and driving the signal low, or (b) as input and reporting a low
	 * value ... without knowing the last value written since the chip
	 * came out of reset (if any).  We can't read the latched output.
	 *
	 * In short, the only reliable solution for setting up pin direction
	 * is to do it explicitly.  The setup() method can do that, but it
	 * may cause transient glitching since it can't know the last value
	 * written (some pins may need to be driven low).
	 *
	 * Using pdata->n_latch avoids that trouble.  When left initialized
	 * to zero, our software copy of the "latch" then matches the chip's
	 * all-ones reset state.  Otherwise it flags pins to be driven low.
	 */
	gpio->out = ~pdata->n_latch;

	status = gpiochip_add(&gpio->chip);
	if (status < 0)
		goto fail;

	/* NOTE: these chips can issue "some pin-changed" IRQs, which we
	 * don't yet even try to use.  Among other issues, the relevant
	 * genirq state isn't available to modular drivers; and most irq
	 * methods can't be called from sleeping contexts.
	 */

	dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
			gpio->chip.base,
			gpio->chip.base + gpio->chip.ngpio - 1,
			client->name,
			client->irq ? " (irq ignored)" : "");

	/* Let platform code set up the GPIOs and their users.
	 * Now is the first time anyone could use them.
	 */
	if (pdata->setup) {
		status = pdata->setup(client,
				gpio->chip.base, gpio->chip.ngpio,
				pdata->context);
		if (status < 0)
			dev_warn(&client->dev, "setup --> %d\n", status);
	}

	return 0;

fail:
	dev_dbg(&client->dev, "probe error %d for '%s'\n",
			status, client->name);
	kfree(gpio);
	return status;
}

static int pcf857x_remove(struct i2c_client *client)
{
	struct pcf857x_platform_data	*pdata = client->dev.platform_data;
	struct pcf857x			*gpio = i2c_get_clientdata(client);
	int				status = 0;

	if (pdata->teardown) {
		status = pdata->teardown(client,
				gpio->chip.base, gpio->chip.ngpio,
				pdata->context);
		if (status < 0) {
			dev_err(&client->dev, "%s --> %d\n",
					"teardown", status);
			return status;
		}
	}

	status = gpiochip_remove(&gpio->chip);
	if (status == 0)
		kfree(gpio);
	else
		dev_err(&client->dev, "%s --> %d\n", "remove", status);
	return status;
}

static struct i2c_driver pcf857x_driver = {
	.driver = {
		.name	= "pcf857x",
		.owner	= THIS_MODULE,
	},
	.probe	= pcf857x_probe,
	.remove	= pcf857x_remove,
};

static int __init pcf857x_init(void)
{
	return i2c_add_driver(&pcf857x_driver);
}
module_init(pcf857x_init);

static void __exit pcf857x_exit(void)
{
	i2c_del_driver(&pcf857x_driver);
}
module_exit(pcf857x_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Brownell");