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 static const struct i2c_device_id pcf857x_id[] = {
30 { "pcf8574", 8 },
31 { "pca8574", 8 },
32 { "pca9670", 8 },
33 { "pca9672", 8 },
34 { "pca9674", 8 },
35 { "pcf8575", 16 },
36 { "pca8575", 16 },
37 { "pca9671", 16 },
38 { "pca9673", 16 },
39 { "pca9675", 16 },
40 { "max7328", 8 },
41 { "max7329", 8 },
42 { }
43 };
44 MODULE_DEVICE_TABLE(i2c, pcf857x_id);
45
46 /*
47 * The pcf857x, pca857x, and pca967x chips only expose one read and one
48 * write register. Writing a "one" bit (to match the reset state) lets
49 * that pin be used as an input; it's not an open-drain model, but acts
50 * a bit like one. This is described as "quasi-bidirectional"; read the
51 * chip documentation for details.
52 *
53 * Many other I2C GPIO expander chips (like the pca953x models) have
54 * more complex register models and more conventional circuitry using
55 * push/pull drivers. They often use the same 0x20..0x27 addresses as
56 * pcf857x parts, making the "legacy" I2C driver model problematic.
57 */
58 struct pcf857x {
59 struct gpio_chip chip;
60 struct i2c_client *client;
61 struct mutex lock; /* protect 'out' */
62 unsigned out; /* software latch */
63 };
64
65 /*-------------------------------------------------------------------------*/
66
67 /* Talk to 8-bit I/O expander */
68
pcf857x_input8(struct gpio_chip * chip,unsigned offset)69 static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
70 {
71 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
72 int status;
73
74 mutex_lock(&gpio->lock);
75 gpio->out |= (1 << offset);
76 status = i2c_smbus_write_byte(gpio->client, gpio->out);
77 mutex_unlock(&gpio->lock);
78
79 return status;
80 }
81
pcf857x_get8(struct gpio_chip * chip,unsigned offset)82 static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
83 {
84 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
85 s32 value;
86
87 value = i2c_smbus_read_byte(gpio->client);
88 return (value < 0) ? 0 : (value & (1 << offset));
89 }
90
pcf857x_output8(struct gpio_chip * chip,unsigned offset,int value)91 static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
92 {
93 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
94 unsigned bit = 1 << offset;
95 int status;
96
97 mutex_lock(&gpio->lock);
98 if (value)
99 gpio->out |= bit;
100 else
101 gpio->out &= ~bit;
102 status = i2c_smbus_write_byte(gpio->client, gpio->out);
103 mutex_unlock(&gpio->lock);
104
105 return status;
106 }
107
pcf857x_set8(struct gpio_chip * chip,unsigned offset,int value)108 static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
109 {
110 pcf857x_output8(chip, offset, value);
111 }
112
113 /*-------------------------------------------------------------------------*/
114
115 /* Talk to 16-bit I/O expander */
116
i2c_write_le16(struct i2c_client * client,u16 word)117 static int i2c_write_le16(struct i2c_client *client, u16 word)
118 {
119 u8 buf[2] = { word & 0xff, word >> 8, };
120 int status;
121
122 status = i2c_master_send(client, buf, 2);
123 return (status < 0) ? status : 0;
124 }
125
i2c_read_le16(struct i2c_client * client)126 static int i2c_read_le16(struct i2c_client *client)
127 {
128 u8 buf[2];
129 int status;
130
131 status = i2c_master_recv(client, buf, 2);
132 if (status < 0)
133 return status;
134 return (buf[1] << 8) | buf[0];
135 }
136
pcf857x_input16(struct gpio_chip * chip,unsigned offset)137 static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
138 {
139 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
140 int status;
141
142 mutex_lock(&gpio->lock);
143 gpio->out |= (1 << offset);
144 status = i2c_write_le16(gpio->client, gpio->out);
145 mutex_unlock(&gpio->lock);
146
147 return status;
148 }
149
pcf857x_get16(struct gpio_chip * chip,unsigned offset)150 static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
151 {
152 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
153 int value;
154
155 value = i2c_read_le16(gpio->client);
156 return (value < 0) ? 0 : (value & (1 << offset));
157 }
158
pcf857x_output16(struct gpio_chip * chip,unsigned offset,int value)159 static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
160 {
161 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
162 unsigned bit = 1 << offset;
163 int status;
164
165 mutex_lock(&gpio->lock);
166 if (value)
167 gpio->out |= bit;
168 else
169 gpio->out &= ~bit;
170 status = i2c_write_le16(gpio->client, gpio->out);
171 mutex_unlock(&gpio->lock);
172
173 return status;
174 }
175
pcf857x_set16(struct gpio_chip * chip,unsigned offset,int value)176 static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
177 {
178 pcf857x_output16(chip, offset, value);
179 }
180
181 /*-------------------------------------------------------------------------*/
182
pcf857x_probe(struct i2c_client * client,const struct i2c_device_id * id)183 static int pcf857x_probe(struct i2c_client *client,
184 const struct i2c_device_id *id)
185 {
186 struct pcf857x_platform_data *pdata;
187 struct pcf857x *gpio;
188 int status;
189
190 pdata = client->dev.platform_data;
191 if (!pdata) {
192 dev_dbg(&client->dev, "no platform data\n");
193 return -EINVAL;
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->gpio_base;
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->n_latch;
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, "gpios %d..%d on a %s%s\n",
294 gpio->chip.base,
295 gpio->chip.base + gpio->chip.ngpio - 1,
296 client->name,
297 client->irq ? " (irq ignored)" : "");
298
299 /* Let platform code set up the GPIOs and their users.
300 * Now is the first time anyone could use them.
301 */
302 if (pdata->setup) {
303 status = pdata->setup(client,
304 gpio->chip.base, gpio->chip.ngpio,
305 pdata->context);
306 if (status < 0)
307 dev_warn(&client->dev, "setup --> %d\n", status);
308 }
309
310 return 0;
311
312 fail:
313 dev_dbg(&client->dev, "probe error %d for '%s'\n",
314 status, client->name);
315 kfree(gpio);
316 return status;
317 }
318
pcf857x_remove(struct i2c_client * client)319 static int pcf857x_remove(struct i2c_client *client)
320 {
321 struct pcf857x_platform_data *pdata = client->dev.platform_data;
322 struct pcf857x *gpio = i2c_get_clientdata(client);
323 int status = 0;
324
325 if (pdata->teardown) {
326 status = pdata->teardown(client,
327 gpio->chip.base, gpio->chip.ngpio,
328 pdata->context);
329 if (status < 0) {
330 dev_err(&client->dev, "%s --> %d\n",
331 "teardown", status);
332 return status;
333 }
334 }
335
336 status = gpiochip_remove(&gpio->chip);
337 if (status == 0)
338 kfree(gpio);
339 else
340 dev_err(&client->dev, "%s --> %d\n", "remove", status);
341 return status;
342 }
343
344 static struct i2c_driver pcf857x_driver = {
345 .driver = {
346 .name = "pcf857x",
347 .owner = THIS_MODULE,
348 },
349 .probe = pcf857x_probe,
350 .remove = pcf857x_remove,
351 .id_table = pcf857x_id,
352 };
353
pcf857x_init(void)354 static int __init pcf857x_init(void)
355 {
356 return i2c_add_driver(&pcf857x_driver);
357 }
358 /* register after i2c postcore initcall and before
359 * subsys initcalls that may rely on these GPIOs
360 */
361 subsys_initcall(pcf857x_init);
362
pcf857x_exit(void)363 static void __exit pcf857x_exit(void)
364 {
365 i2c_del_driver(&pcf857x_driver);
366 }
367 module_exit(pcf857x_exit);
368
369 MODULE_LICENSE("GPL");
370 MODULE_AUTHOR("David Brownell");
371