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>
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.
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.
42 struct gpio_chip chip;
43 struct i2c_client *client;
44 unsigned out; /* software latch */
47 /*-------------------------------------------------------------------------*/
49 /* Talk to 8-bit I/O expander */
51 static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
53 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
55 gpio->out |= (1 << offset);
56 return i2c_smbus_write_byte(gpio->client, gpio->out);
59 static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
61 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
64 value = i2c_smbus_read_byte(gpio->client);
65 return (value < 0) ? 0 : (value & (1 << offset));
68 static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
70 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
71 unsigned bit = 1 << offset;
77 return i2c_smbus_write_byte(gpio->client, gpio->out);
80 static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
82 pcf857x_output8(chip, offset, value);
85 /*-------------------------------------------------------------------------*/
87 /* Talk to 16-bit I/O expander */
89 static int i2c_write_le16(struct i2c_client *client, u16 word)
91 u8 buf[2] = { word & 0xff, word >> 8, };
94 status = i2c_master_send(client, buf, 2);
95 return (status < 0) ? status : 0;
98 static int i2c_read_le16(struct i2c_client *client)
103 status = i2c_master_recv(client, buf, 2);
106 return (buf[1] << 8) | buf[0];
109 static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
111 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
113 gpio->out |= (1 << offset);
114 return i2c_write_le16(gpio->client, gpio->out);
117 static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
119 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
122 value = i2c_read_le16(gpio->client);
123 return (value < 0) ? 0 : (value & (1 << offset));
126 static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
128 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
129 unsigned bit = 1 << offset;
135 return i2c_write_le16(gpio->client, gpio->out);
138 static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
140 pcf857x_output16(chip, offset, value);
143 /*-------------------------------------------------------------------------*/
145 static int pcf857x_probe(struct i2c_client *client,
146 const struct i2c_device_id *id)
148 struct pcf857x_platform_data *pdata;
149 struct pcf857x *gpio;
152 pdata = client->dev.platform_data;
156 /* Allocate, initialize, and register this gpio_chip. */
157 gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
161 gpio->chip.base = pdata->gpio_base;
162 gpio->chip.can_sleep = 1;
163 gpio->chip.owner = THIS_MODULE;
165 /* NOTE: the OnSemi jlc1562b is also largely compatible with
166 * these parts, notably for output. It has a low-resolution
167 * DAC instead of pin change IRQs; and its inputs can be the
168 * result of comparators.
171 /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
172 * 9670, 9672, 9764, and 9764a use quite a variety.
174 * NOTE: we don't distinguish here between *4 and *4a parts.
176 if (strcmp(client->name, "pcf8574") == 0
177 || strcmp(client->name, "pca8574") == 0
178 || strcmp(client->name, "pca9670") == 0
179 || strcmp(client->name, "pca9672") == 0
180 || strcmp(client->name, "pca9674") == 0
182 gpio->chip.ngpio = 8;
183 gpio->chip.direction_input = pcf857x_input8;
184 gpio->chip.get = pcf857x_get8;
185 gpio->chip.direction_output = pcf857x_output8;
186 gpio->chip.set = pcf857x_set8;
188 if (!i2c_check_functionality(client->adapter,
189 I2C_FUNC_SMBUS_BYTE))
192 /* fail if there's no chip present */
194 status = i2c_smbus_read_byte(client);
196 /* '75/'75c addresses are 0x20..0x27, just like the '74;
197 * the '75c doesn't have a current source pulling high.
198 * 9671, 9673, and 9765 use quite a variety of addresses.
200 * NOTE: we don't distinguish here between '75 and '75c parts.
202 } else if (strcmp(client->name, "pcf8575") == 0
203 || strcmp(client->name, "pca8575") == 0
204 || strcmp(client->name, "pca9671") == 0
205 || strcmp(client->name, "pca9673") == 0
206 || strcmp(client->name, "pca9675") == 0
208 gpio->chip.ngpio = 16;
209 gpio->chip.direction_input = pcf857x_input16;
210 gpio->chip.get = pcf857x_get16;
211 gpio->chip.direction_output = pcf857x_output16;
212 gpio->chip.set = pcf857x_set16;
214 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
217 /* fail if there's no chip present */
219 status = i2c_read_le16(client);
227 gpio->chip.label = client->name;
229 gpio->client = client;
230 i2c_set_clientdata(client, gpio);
232 /* NOTE: these chips have strange "quasi-bidirectional" I/O pins.
233 * We can't actually know whether a pin is configured (a) as output
234 * and driving the signal low, or (b) as input and reporting a low
235 * value ... without knowing the last value written since the chip
236 * came out of reset (if any). We can't read the latched output.
238 * In short, the only reliable solution for setting up pin direction
239 * is to do it explicitly. The setup() method can do that, but it
240 * may cause transient glitching since it can't know the last value
241 * written (some pins may need to be driven low).
243 * Using pdata->n_latch avoids that trouble. When left initialized
244 * to zero, our software copy of the "latch" then matches the chip's
245 * all-ones reset state. Otherwise it flags pins to be driven low.
247 gpio->out = ~pdata->n_latch;
249 status = gpiochip_add(&gpio->chip);
253 /* NOTE: these chips can issue "some pin-changed" IRQs, which we
254 * don't yet even try to use. Among other issues, the relevant
255 * genirq state isn't available to modular drivers; and most irq
256 * methods can't be called from sleeping contexts.
259 dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
261 gpio->chip.base + gpio->chip.ngpio - 1,
263 client->irq ? " (irq ignored)" : "");
265 /* Let platform code set up the GPIOs and their users.
266 * Now is the first time anyone could use them.
269 status = pdata->setup(client,
270 gpio->chip.base, gpio->chip.ngpio,
273 dev_warn(&client->dev, "setup --> %d\n", status);
279 dev_dbg(&client->dev, "probe error %d for '%s'\n",
280 status, client->name);
285 static int pcf857x_remove(struct i2c_client *client)
287 struct pcf857x_platform_data *pdata = client->dev.platform_data;
288 struct pcf857x *gpio = i2c_get_clientdata(client);
291 if (pdata->teardown) {
292 status = pdata->teardown(client,
293 gpio->chip.base, gpio->chip.ngpio,
296 dev_err(&client->dev, "%s --> %d\n",
302 status = gpiochip_remove(&gpio->chip);
306 dev_err(&client->dev, "%s --> %d\n", "remove", status);
310 static struct i2c_driver pcf857x_driver = {
313 .owner = THIS_MODULE,
315 .probe = pcf857x_probe,
316 .remove = pcf857x_remove,
319 static int __init pcf857x_init(void)
321 return i2c_add_driver(&pcf857x_driver);
323 module_init(pcf857x_init);
325 static void __exit pcf857x_exit(void)
327 i2c_del_driver(&pcf857x_driver);
329 module_exit(pcf857x_exit);
331 MODULE_LICENSE("GPL");
332 MODULE_AUTHOR("David Brownell");