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