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[] = {
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");
197 /* Allocate, initialize, and register this gpio_chip. */
198 gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
202 mutex_init(&gpio->lock);
204 gpio->chip.base = pdata->gpio_base;
205 gpio->chip.can_sleep = 1;
206 gpio->chip.dev = &client->dev;
207 gpio->chip.owner = THIS_MODULE;
209 /* NOTE: the OnSemi jlc1562b is also largely compatible with
210 * these parts, notably for output. It has a low-resolution
211 * DAC instead of pin change IRQs; and its inputs can be the
212 * result of comparators.
215 /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
216 * 9670, 9672, 9764, and 9764a use quite a variety.
218 * NOTE: we don't distinguish here between *4 and *4a parts.
220 gpio->chip.ngpio = id->driver_data;
221 if (gpio->chip.ngpio == 8) {
222 gpio->chip.direction_input = pcf857x_input8;
223 gpio->chip.get = pcf857x_get8;
224 gpio->chip.direction_output = pcf857x_output8;
225 gpio->chip.set = pcf857x_set8;
227 if (!i2c_check_functionality(client->adapter,
228 I2C_FUNC_SMBUS_BYTE))
231 /* fail if there's no chip present */
233 status = i2c_smbus_read_byte(client);
235 /* '75/'75c addresses are 0x20..0x27, just like the '74;
236 * the '75c doesn't have a current source pulling high.
237 * 9671, 9673, and 9765 use quite a variety of addresses.
239 * NOTE: we don't distinguish here between '75 and '75c parts.
241 } else if (gpio->chip.ngpio == 16) {
242 gpio->chip.direction_input = pcf857x_input16;
243 gpio->chip.get = pcf857x_get16;
244 gpio->chip.direction_output = pcf857x_output16;
245 gpio->chip.set = pcf857x_set16;
247 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
250 /* fail if there's no chip present */
252 status = i2c_read_le16(client);
255 dev_dbg(&client->dev, "unsupported number of gpios\n");
262 gpio->chip.label = client->name;
264 gpio->client = client;
265 i2c_set_clientdata(client, gpio);
267 /* NOTE: these chips have strange "quasi-bidirectional" I/O pins.
268 * We can't actually know whether a pin is configured (a) as output
269 * and driving the signal low, or (b) as input and reporting a low
270 * value ... without knowing the last value written since the chip
271 * came out of reset (if any). We can't read the latched output.
273 * In short, the only reliable solution for setting up pin direction
274 * is to do it explicitly. The setup() method can do that, but it
275 * may cause transient glitching since it can't know the last value
276 * written (some pins may need to be driven low).
278 * Using pdata->n_latch avoids that trouble. When left initialized
279 * to zero, our software copy of the "latch" then matches the chip's
280 * all-ones reset state. Otherwise it flags pins to be driven low.
282 gpio->out = ~pdata->n_latch;
284 status = gpiochip_add(&gpio->chip);
288 /* NOTE: these chips can issue "some pin-changed" IRQs, which we
289 * don't yet even try to use. Among other issues, the relevant
290 * genirq state isn't available to modular drivers; and most irq
291 * methods can't be called from sleeping contexts.
294 dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
296 gpio->chip.base + gpio->chip.ngpio - 1,
298 client->irq ? " (irq ignored)" : "");
300 /* Let platform code set up the GPIOs and their users.
301 * Now is the first time anyone could use them.
304 status = pdata->setup(client,
305 gpio->chip.base, gpio->chip.ngpio,
308 dev_warn(&client->dev, "setup --> %d\n", status);
314 dev_dbg(&client->dev, "probe error %d for '%s'\n",
315 status, client->name);
320 static int pcf857x_remove(struct i2c_client *client)
322 struct pcf857x_platform_data *pdata = client->dev.platform_data;
323 struct pcf857x *gpio = i2c_get_clientdata(client);
326 if (pdata->teardown) {
327 status = pdata->teardown(client,
328 gpio->chip.base, gpio->chip.ngpio,
331 dev_err(&client->dev, "%s --> %d\n",
337 status = gpiochip_remove(&gpio->chip);
341 dev_err(&client->dev, "%s --> %d\n", "remove", status);
345 static struct i2c_driver pcf857x_driver = {
348 .owner = THIS_MODULE,
350 .probe = pcf857x_probe,
351 .remove = pcf857x_remove,
352 .id_table = pcf857x_id,
355 static int __init pcf857x_init(void)
357 return i2c_add_driver(&pcf857x_driver);
359 /* register after i2c postcore initcall and before
360 * subsys initcalls that may rely on these GPIOs
362 subsys_initcall(pcf857x_init);
364 static void __exit pcf857x_exit(void)
366 i2c_del_driver(&pcf857x_driver);
368 module_exit(pcf857x_exit);
370 MODULE_LICENSE("GPL");
371 MODULE_AUTHOR("David Brownell");