2 * pcf857x - driver for pcf857x, pca857x, and pca967x I2C GPIO expanders
4 * Copyright (C) 2007 David Brownell
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.
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.
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.
21 #include <linux/kernel.h>
22 #include <linux/slab.h>
23 #include <linux/i2c.h>
24 #include <linux/i2c/pcf857x.h>
29 static const struct i2c_device_id pcf857x_id[] = {
44 MODULE_DEVICE_TABLE(i2c, pcf857x_id);
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.
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.
59 struct gpio_chip chip;
60 struct i2c_client *client;
61 struct mutex lock; /* protect 'out' */
62 unsigned out; /* software latch */
65 /*-------------------------------------------------------------------------*/
67 /* Talk to 8-bit I/O expander */
69 static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
71 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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);
82 static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
84 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
87 value = i2c_smbus_read_byte(gpio->client);
88 return (value < 0) ? 0 : (value & (1 << offset));
91 static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
93 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
94 unsigned bit = 1 << offset;
97 mutex_lock(&gpio->lock);
102 status = i2c_smbus_write_byte(gpio->client, gpio->out);
103 mutex_unlock(&gpio->lock);
108 static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
110 pcf857x_output8(chip, offset, value);
113 /*-------------------------------------------------------------------------*/
115 /* Talk to 16-bit I/O expander */
117 static int i2c_write_le16(struct i2c_client *client, u16 word)
119 u8 buf[2] = { word & 0xff, word >> 8, };
122 status = i2c_master_send(client, buf, 2);
123 return (status < 0) ? status : 0;
126 static int i2c_read_le16(struct i2c_client *client)
131 status = i2c_master_recv(client, buf, 2);
134 return (buf[1] << 8) | buf[0];
137 static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
139 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
142 mutex_lock(&gpio->lock);
143 gpio->out |= (1 << offset);
144 status = i2c_write_le16(gpio->client, gpio->out);
145 mutex_unlock(&gpio->lock);
150 static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
152 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
155 value = i2c_read_le16(gpio->client);
156 return (value < 0) ? 0 : (value & (1 << offset));
159 static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
161 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
162 unsigned bit = 1 << offset;
165 mutex_lock(&gpio->lock);
170 status = i2c_write_le16(gpio->client, gpio->out);
171 mutex_unlock(&gpio->lock);
176 static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
178 pcf857x_output16(chip, offset, value);
181 /*-------------------------------------------------------------------------*/
183 static int pcf857x_probe(struct i2c_client *client,
184 const struct i2c_device_id *id)
186 struct pcf857x_platform_data *pdata;
187 struct pcf857x *gpio;
190 pdata = client->dev.platform_data;
194 /* Allocate, initialize, and register this gpio_chip. */
195 gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
199 mutex_init(&gpio->lock);
201 gpio->chip.base = pdata->gpio_base;
202 gpio->chip.can_sleep = 1;
203 gpio->chip.owner = THIS_MODULE;
205 /* NOTE: the OnSemi jlc1562b is also largely compatible with
206 * these parts, notably for output. It has a low-resolution
207 * DAC instead of pin change IRQs; and its inputs can be the
208 * result of comparators.
211 /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
212 * 9670, 9672, 9764, and 9764a use quite a variety.
214 * NOTE: we don't distinguish here between *4 and *4a parts.
216 gpio->chip.ngpio = id->driver_data;
217 if (gpio->chip.ngpio == 8) {
218 gpio->chip.direction_input = pcf857x_input8;
219 gpio->chip.get = pcf857x_get8;
220 gpio->chip.direction_output = pcf857x_output8;
221 gpio->chip.set = pcf857x_set8;
223 if (!i2c_check_functionality(client->adapter,
224 I2C_FUNC_SMBUS_BYTE))
227 /* fail if there's no chip present */
229 status = i2c_smbus_read_byte(client);
231 /* '75/'75c addresses are 0x20..0x27, just like the '74;
232 * the '75c doesn't have a current source pulling high.
233 * 9671, 9673, and 9765 use quite a variety of addresses.
235 * NOTE: we don't distinguish here between '75 and '75c parts.
237 } else if (gpio->chip.ngpio == 16) {
238 gpio->chip.direction_input = pcf857x_input16;
239 gpio->chip.get = pcf857x_get16;
240 gpio->chip.direction_output = pcf857x_output16;
241 gpio->chip.set = pcf857x_set16;
243 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
246 /* fail if there's no chip present */
248 status = i2c_read_le16(client);
256 gpio->chip.label = client->name;
258 gpio->client = client;
259 i2c_set_clientdata(client, gpio);
261 /* NOTE: these chips have strange "quasi-bidirectional" I/O pins.
262 * We can't actually know whether a pin is configured (a) as output
263 * and driving the signal low, or (b) as input and reporting a low
264 * value ... without knowing the last value written since the chip
265 * came out of reset (if any). We can't read the latched output.
267 * In short, the only reliable solution for setting up pin direction
268 * is to do it explicitly. The setup() method can do that, but it
269 * may cause transient glitching since it can't know the last value
270 * written (some pins may need to be driven low).
272 * Using pdata->n_latch avoids that trouble. When left initialized
273 * to zero, our software copy of the "latch" then matches the chip's
274 * all-ones reset state. Otherwise it flags pins to be driven low.
276 gpio->out = ~pdata->n_latch;
278 status = gpiochip_add(&gpio->chip);
282 /* NOTE: these chips can issue "some pin-changed" IRQs, which we
283 * don't yet even try to use. Among other issues, the relevant
284 * genirq state isn't available to modular drivers; and most irq
285 * methods can't be called from sleeping contexts.
288 dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
290 gpio->chip.base + gpio->chip.ngpio - 1,
292 client->irq ? " (irq ignored)" : "");
294 /* Let platform code set up the GPIOs and their users.
295 * Now is the first time anyone could use them.
298 status = pdata->setup(client,
299 gpio->chip.base, gpio->chip.ngpio,
302 dev_warn(&client->dev, "setup --> %d\n", status);
308 dev_dbg(&client->dev, "probe error %d for '%s'\n",
309 status, client->name);
314 static int pcf857x_remove(struct i2c_client *client)
316 struct pcf857x_platform_data *pdata = client->dev.platform_data;
317 struct pcf857x *gpio = i2c_get_clientdata(client);
320 if (pdata->teardown) {
321 status = pdata->teardown(client,
322 gpio->chip.base, gpio->chip.ngpio,
325 dev_err(&client->dev, "%s --> %d\n",
331 status = gpiochip_remove(&gpio->chip);
335 dev_err(&client->dev, "%s --> %d\n", "remove", status);
339 static struct i2c_driver pcf857x_driver = {
342 .owner = THIS_MODULE,
344 .probe = pcf857x_probe,
345 .remove = pcf857x_remove,
346 .id_table = pcf857x_id,
349 static int __init pcf857x_init(void)
351 return i2c_add_driver(&pcf857x_driver);
353 module_init(pcf857x_init);
355 static void __exit pcf857x_exit(void)
357 i2c_del_driver(&pcf857x_driver);
359 module_exit(pcf857x_exit);
361 MODULE_LICENSE("GPL");
362 MODULE_AUTHOR("David Brownell");