2 * 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/gpio.h>
24 #include <linux/i2c.h>
25 #include <linux/i2c/pcf857x.h>
26 #include <linux/module.h>
29 static const struct i2c_device_id pcf857x_id[] = {
45 MODULE_DEVICE_TABLE(i2c, pcf857x_id);
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.
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.
60 struct gpio_chip chip;
61 struct i2c_client *client;
62 struct mutex lock; /* protect 'out' */
63 unsigned out; /* software latch */
66 /*-------------------------------------------------------------------------*/
68 /* Talk to 8-bit I/O expander */
70 static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
72 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
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);
83 static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
85 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
88 value = i2c_smbus_read_byte(gpio->client);
89 return (value < 0) ? 0 : (value & (1 << offset));
92 static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
94 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
95 unsigned bit = 1 << offset;
98 mutex_lock(&gpio->lock);
103 status = i2c_smbus_write_byte(gpio->client, gpio->out);
104 mutex_unlock(&gpio->lock);
109 static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
111 pcf857x_output8(chip, offset, value);
114 /*-------------------------------------------------------------------------*/
116 /* Talk to 16-bit I/O expander */
118 static int i2c_write_le16(struct i2c_client *client, u16 word)
120 u8 buf[2] = { word & 0xff, word >> 8, };
123 status = i2c_master_send(client, buf, 2);
124 return (status < 0) ? status : 0;
127 static int i2c_read_le16(struct i2c_client *client)
132 status = i2c_master_recv(client, buf, 2);
135 return (buf[1] << 8) | buf[0];
138 static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
140 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
143 mutex_lock(&gpio->lock);
144 gpio->out |= (1 << offset);
145 status = i2c_write_le16(gpio->client, gpio->out);
146 mutex_unlock(&gpio->lock);
151 static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
153 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
156 value = i2c_read_le16(gpio->client);
157 return (value < 0) ? 0 : (value & (1 << offset));
160 static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
162 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
163 unsigned bit = 1 << offset;
166 mutex_lock(&gpio->lock);
171 status = i2c_write_le16(gpio->client, gpio->out);
172 mutex_unlock(&gpio->lock);
177 static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
179 pcf857x_output16(chip, offset, value);
182 /*-------------------------------------------------------------------------*/
184 static int pcf857x_probe(struct i2c_client *client,
185 const struct i2c_device_id *id)
187 struct pcf857x_platform_data *pdata;
188 struct pcf857x *gpio;
191 pdata = client->dev.platform_data;
193 dev_dbg(&client->dev, "no platform data\n");
196 /* Allocate, initialize, and register this gpio_chip. */
197 gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
201 mutex_init(&gpio->lock);
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;
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.
214 /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
215 * 9670, 9672, 9764, and 9764a use quite a variety.
217 * NOTE: we don't distinguish here between *4 and *4a parts.
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;
226 if (!i2c_check_functionality(client->adapter,
227 I2C_FUNC_SMBUS_BYTE))
230 /* fail if there's no chip present */
232 status = i2c_smbus_read_byte(client);
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.
238 * NOTE: we don't distinguish here between '75 and '75c parts.
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;
246 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
249 /* fail if there's no chip present */
251 status = i2c_read_le16(client);
254 dev_dbg(&client->dev, "unsupported number of gpios\n");
261 gpio->chip.label = client->name;
263 gpio->client = client;
264 i2c_set_clientdata(client, gpio);
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.
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).
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.
281 gpio->out = pdata ? ~pdata->n_latch : ~0;
283 status = gpiochip_add(&gpio->chip);
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.
293 dev_info(&client->dev, "%s\n",
294 client->irq ? " (irq ignored)" : "");
296 /* Let platform code set up the GPIOs and their users.
297 * Now is the first time anyone could use them.
299 if (pdata && pdata->setup) {
300 status = pdata->setup(client,
301 gpio->chip.base, gpio->chip.ngpio,
304 dev_warn(&client->dev, "setup --> %d\n", status);
310 dev_dbg(&client->dev, "probe error %d for '%s'\n",
311 status, client->name);
316 static int pcf857x_remove(struct i2c_client *client)
318 struct pcf857x_platform_data *pdata = client->dev.platform_data;
319 struct pcf857x *gpio = i2c_get_clientdata(client);
322 if (pdata && pdata->teardown) {
323 status = pdata->teardown(client,
324 gpio->chip.base, gpio->chip.ngpio,
327 dev_err(&client->dev, "%s --> %d\n",
333 status = gpiochip_remove(&gpio->chip);
337 dev_err(&client->dev, "%s --> %d\n", "remove", status);
341 static struct i2c_driver pcf857x_driver = {
344 .owner = THIS_MODULE,
346 .probe = pcf857x_probe,
347 .remove = pcf857x_remove,
348 .id_table = pcf857x_id,
351 static int __init pcf857x_init(void)
353 return i2c_add_driver(&pcf857x_driver);
355 /* register after i2c postcore initcall and before
356 * subsys initcalls that may rely on these GPIOs
358 subsys_initcall(pcf857x_init);
360 static void __exit pcf857x_exit(void)
362 i2c_del_driver(&pcf857x_driver);
364 module_exit(pcf857x_exit);
366 MODULE_LICENSE("GPL");
367 MODULE_AUTHOR("David Brownell");