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 */
65 int (*write
)(struct i2c_client
*client
, unsigned data
);
66 int (*read
)(struct i2c_client
*client
);
69 /*-------------------------------------------------------------------------*/
71 /* Talk to 8-bit I/O expander */
73 static int i2c_write_le8(struct i2c_client
*client
, unsigned data
)
75 return i2c_smbus_write_byte(client
, data
);
78 static int i2c_read_le8(struct i2c_client
*client
)
80 return (int)i2c_smbus_read_byte(client
);
83 /* Talk to 16-bit I/O expander */
85 static int i2c_write_le16(struct i2c_client
*client
, unsigned word
)
87 u8 buf
[2] = { word
& 0xff, word
>> 8, };
90 status
= i2c_master_send(client
, buf
, 2);
91 return (status
< 0) ? status
: 0;
94 static int i2c_read_le16(struct i2c_client
*client
)
99 status
= i2c_master_recv(client
, buf
, 2);
102 return (buf
[1] << 8) | buf
[0];
105 /*-------------------------------------------------------------------------*/
107 static int pcf857x_input(struct gpio_chip
*chip
, unsigned offset
)
109 struct pcf857x
*gpio
= container_of(chip
, struct pcf857x
, chip
);
112 mutex_lock(&gpio
->lock
);
113 gpio
->out
|= (1 << offset
);
114 status
= gpio
->write(gpio
->client
, gpio
->out
);
115 mutex_unlock(&gpio
->lock
);
120 static int pcf857x_get(struct gpio_chip
*chip
, unsigned offset
)
122 struct pcf857x
*gpio
= container_of(chip
, struct pcf857x
, chip
);
125 value
= gpio
->read(gpio
->client
);
126 return (value
< 0) ? 0 : (value
& (1 << offset
));
129 static int pcf857x_output(struct gpio_chip
*chip
, unsigned offset
, int value
)
131 struct pcf857x
*gpio
= container_of(chip
, struct pcf857x
, chip
);
132 unsigned bit
= 1 << offset
;
135 mutex_lock(&gpio
->lock
);
140 status
= gpio
->write(gpio
->client
, gpio
->out
);
141 mutex_unlock(&gpio
->lock
);
146 static void pcf857x_set(struct gpio_chip
*chip
, unsigned offset
, int value
)
148 pcf857x_output(chip
, offset
, value
);
151 /*-------------------------------------------------------------------------*/
153 static int pcf857x_probe(struct i2c_client
*client
,
154 const struct i2c_device_id
*id
)
156 struct pcf857x_platform_data
*pdata
;
157 struct pcf857x
*gpio
;
160 pdata
= client
->dev
.platform_data
;
162 dev_dbg(&client
->dev
, "no platform data\n");
165 /* Allocate, initialize, and register this gpio_chip. */
166 gpio
= kzalloc(sizeof *gpio
, GFP_KERNEL
);
170 mutex_init(&gpio
->lock
);
172 gpio
->chip
.base
= pdata
? pdata
->gpio_base
: -1;
173 gpio
->chip
.can_sleep
= 1;
174 gpio
->chip
.dev
= &client
->dev
;
175 gpio
->chip
.owner
= THIS_MODULE
;
176 gpio
->chip
.get
= pcf857x_get
;
177 gpio
->chip
.set
= pcf857x_set
;
178 gpio
->chip
.direction_input
= pcf857x_input
;
179 gpio
->chip
.direction_output
= pcf857x_output
;
180 gpio
->chip
.ngpio
= id
->driver_data
;
182 /* NOTE: the OnSemi jlc1562b is also largely compatible with
183 * these parts, notably for output. It has a low-resolution
184 * DAC instead of pin change IRQs; and its inputs can be the
185 * result of comparators.
188 /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
189 * 9670, 9672, 9764, and 9764a use quite a variety.
191 * NOTE: we don't distinguish here between *4 and *4a parts.
193 if (gpio
->chip
.ngpio
== 8) {
194 gpio
->write
= i2c_write_le8
;
195 gpio
->read
= i2c_read_le8
;
197 if (!i2c_check_functionality(client
->adapter
,
198 I2C_FUNC_SMBUS_BYTE
))
201 /* fail if there's no chip present */
203 status
= i2c_smbus_read_byte(client
);
205 /* '75/'75c addresses are 0x20..0x27, just like the '74;
206 * the '75c doesn't have a current source pulling high.
207 * 9671, 9673, and 9765 use quite a variety of addresses.
209 * NOTE: we don't distinguish here between '75 and '75c parts.
211 } else if (gpio
->chip
.ngpio
== 16) {
212 gpio
->write
= i2c_write_le16
;
213 gpio
->read
= i2c_read_le16
;
215 if (!i2c_check_functionality(client
->adapter
, I2C_FUNC_I2C
))
218 /* fail if there's no chip present */
220 status
= i2c_read_le16(client
);
223 dev_dbg(&client
->dev
, "unsupported number of gpios\n");
230 gpio
->chip
.label
= client
->name
;
232 gpio
->client
= client
;
233 i2c_set_clientdata(client
, gpio
);
235 /* NOTE: these chips have strange "quasi-bidirectional" I/O pins.
236 * We can't actually know whether a pin is configured (a) as output
237 * and driving the signal low, or (b) as input and reporting a low
238 * value ... without knowing the last value written since the chip
239 * came out of reset (if any). We can't read the latched output.
241 * In short, the only reliable solution for setting up pin direction
242 * is to do it explicitly. The setup() method can do that, but it
243 * may cause transient glitching since it can't know the last value
244 * written (some pins may need to be driven low).
246 * Using pdata->n_latch avoids that trouble. When left initialized
247 * to zero, our software copy of the "latch" then matches the chip's
248 * all-ones reset state. Otherwise it flags pins to be driven low.
250 gpio
->out
= pdata
? ~pdata
->n_latch
: ~0;
252 status
= gpiochip_add(&gpio
->chip
);
256 /* NOTE: these chips can issue "some pin-changed" IRQs, which we
257 * don't yet even try to use. Among other issues, the relevant
258 * genirq state isn't available to modular drivers; and most irq
259 * methods can't be called from sleeping contexts.
262 dev_info(&client
->dev
, "%s\n",
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.
268 if (pdata
&& pdata
->setup
) {
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
&& 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
,
317 .id_table
= pcf857x_id
,
320 static int __init
pcf857x_init(void)
322 return i2c_add_driver(&pcf857x_driver
);
324 /* register after i2c postcore initcall and before
325 * subsys initcalls that may rely on these GPIOs
327 subsys_initcall(pcf857x_init
);
329 static void __exit
pcf857x_exit(void)
331 i2c_del_driver(&pcf857x_driver
);
333 module_exit(pcf857x_exit
);
335 MODULE_LICENSE("GPL");
336 MODULE_AUTHOR("David Brownell");