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1 | /* |
2 | * pcf857x - driver for pcf857x, pca857x, and pca967x I2C GPIO expanders | |
3 | * | |
4 | * Copyright (C) 2007 David Brownell | |
5 | * | |
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. | |
10 | * | |
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. | |
15 | * | |
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. | |
19 | */ | |
20 | ||
21 | #include <linux/kernel.h> | |
22 | #include <linux/slab.h> | |
23 | #include <linux/i2c.h> | |
24 | #include <linux/i2c/pcf857x.h> | |
25 | ||
26 | #include <asm/gpio.h> | |
27 | ||
28 | ||
29 | /* | |
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. | |
35 | * | |
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. | |
40 | */ | |
41 | struct pcf857x { | |
42 | struct gpio_chip chip; | |
43 | struct i2c_client *client; | |
44 | unsigned out; /* software latch */ | |
45 | }; | |
46 | ||
47 | /*-------------------------------------------------------------------------*/ | |
48 | ||
49 | /* Talk to 8-bit I/O expander */ | |
50 | ||
51 | static int pcf857x_input8(struct gpio_chip *chip, unsigned offset) | |
52 | { | |
53 | struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); | |
54 | ||
55 | gpio->out |= (1 << offset); | |
56 | return i2c_smbus_write_byte(gpio->client, gpio->out); | |
57 | } | |
58 | ||
59 | static int pcf857x_get8(struct gpio_chip *chip, unsigned offset) | |
60 | { | |
61 | struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); | |
62 | s32 value; | |
63 | ||
64 | value = i2c_smbus_read_byte(gpio->client); | |
65 | return (value < 0) ? 0 : (value & (1 << offset)); | |
66 | } | |
67 | ||
68 | static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value) | |
69 | { | |
70 | struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); | |
71 | unsigned bit = 1 << offset; | |
72 | ||
73 | if (value) | |
74 | gpio->out |= bit; | |
75 | else | |
76 | gpio->out &= ~bit; | |
77 | return i2c_smbus_write_byte(gpio->client, gpio->out); | |
78 | } | |
79 | ||
80 | static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value) | |
81 | { | |
82 | pcf857x_output8(chip, offset, value); | |
83 | } | |
84 | ||
85 | /*-------------------------------------------------------------------------*/ | |
86 | ||
87 | /* Talk to 16-bit I/O expander */ | |
88 | ||
89 | static int i2c_write_le16(struct i2c_client *client, u16 word) | |
90 | { | |
91 | u8 buf[2] = { word & 0xff, word >> 8, }; | |
92 | int status; | |
93 | ||
94 | status = i2c_master_send(client, buf, 2); | |
95 | return (status < 0) ? status : 0; | |
96 | } | |
97 | ||
98 | static int i2c_read_le16(struct i2c_client *client) | |
99 | { | |
100 | u8 buf[2]; | |
101 | int status; | |
102 | ||
103 | status = i2c_master_recv(client, buf, 2); | |
104 | if (status < 0) | |
105 | return status; | |
106 | return (buf[1] << 8) | buf[0]; | |
107 | } | |
108 | ||
109 | static int pcf857x_input16(struct gpio_chip *chip, unsigned offset) | |
110 | { | |
111 | struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); | |
112 | ||
113 | gpio->out |= (1 << offset); | |
114 | return i2c_write_le16(gpio->client, gpio->out); | |
115 | } | |
116 | ||
117 | static int pcf857x_get16(struct gpio_chip *chip, unsigned offset) | |
118 | { | |
119 | struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); | |
120 | int value; | |
121 | ||
122 | value = i2c_read_le16(gpio->client); | |
123 | return (value < 0) ? 0 : (value & (1 << offset)); | |
124 | } | |
125 | ||
126 | static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value) | |
127 | { | |
128 | struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); | |
129 | unsigned bit = 1 << offset; | |
130 | ||
131 | if (value) | |
132 | gpio->out |= bit; | |
133 | else | |
134 | gpio->out &= ~bit; | |
135 | return i2c_write_le16(gpio->client, gpio->out); | |
136 | } | |
137 | ||
138 | static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value) | |
139 | { | |
140 | pcf857x_output16(chip, offset, value); | |
141 | } | |
142 | ||
143 | /*-------------------------------------------------------------------------*/ | |
144 | ||
145 | static int pcf857x_probe(struct i2c_client *client) | |
146 | { | |
147 | struct pcf857x_platform_data *pdata; | |
148 | struct pcf857x *gpio; | |
149 | int status; | |
150 | ||
151 | pdata = client->dev.platform_data; | |
152 | if (!pdata) | |
153 | return -ENODEV; | |
154 | ||
155 | /* Allocate, initialize, and register this gpio_chip. */ | |
156 | gpio = kzalloc(sizeof *gpio, GFP_KERNEL); | |
157 | if (!gpio) | |
158 | return -ENOMEM; | |
159 | ||
160 | gpio->chip.base = pdata->gpio_base; | |
161 | gpio->chip.can_sleep = 1; | |
162 | ||
163 | /* NOTE: the OnSemi jlc1562b is also largely compatible with | |
164 | * these parts, notably for output. It has a low-resolution | |
165 | * DAC instead of pin change IRQs; and its inputs can be the | |
166 | * result of comparators. | |
167 | */ | |
168 | ||
169 | /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f; | |
170 | * 9670, 9672, 9764, and 9764a use quite a variety. | |
171 | * | |
172 | * NOTE: we don't distinguish here between *4 and *4a parts. | |
173 | */ | |
174 | if (strcmp(client->name, "pcf8574") == 0 | |
175 | || strcmp(client->name, "pca8574") == 0 | |
176 | || strcmp(client->name, "pca9670") == 0 | |
177 | || strcmp(client->name, "pca9672") == 0 | |
178 | || strcmp(client->name, "pca9674") == 0 | |
179 | ) { | |
180 | gpio->chip.ngpio = 8; | |
181 | gpio->chip.direction_input = pcf857x_input8; | |
182 | gpio->chip.get = pcf857x_get8; | |
183 | gpio->chip.direction_output = pcf857x_output8; | |
184 | gpio->chip.set = pcf857x_set8; | |
185 | ||
186 | if (!i2c_check_functionality(client->adapter, | |
187 | I2C_FUNC_SMBUS_BYTE)) | |
188 | status = -EIO; | |
189 | ||
190 | /* fail if there's no chip present */ | |
191 | else | |
192 | status = i2c_smbus_read_byte(client); | |
193 | ||
194 | /* '75/'75c addresses are 0x20..0x27, just like the '74; | |
195 | * the '75c doesn't have a current source pulling high. | |
196 | * 9671, 9673, and 9765 use quite a variety of addresses. | |
197 | * | |
198 | * NOTE: we don't distinguish here between '75 and '75c parts. | |
199 | */ | |
200 | } else if (strcmp(client->name, "pcf8575") == 0 | |
201 | || strcmp(client->name, "pca8575") == 0 | |
202 | || strcmp(client->name, "pca9671") == 0 | |
203 | || strcmp(client->name, "pca9673") == 0 | |
204 | || strcmp(client->name, "pca9675") == 0 | |
205 | ) { | |
206 | gpio->chip.ngpio = 16; | |
207 | gpio->chip.direction_input = pcf857x_input16; | |
208 | gpio->chip.get = pcf857x_get16; | |
209 | gpio->chip.direction_output = pcf857x_output16; | |
210 | gpio->chip.set = pcf857x_set16; | |
211 | ||
212 | if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) | |
213 | status = -EIO; | |
214 | ||
215 | /* fail if there's no chip present */ | |
216 | else | |
217 | status = i2c_read_le16(client); | |
218 | ||
219 | } else | |
220 | status = -ENODEV; | |
221 | ||
222 | if (status < 0) | |
223 | goto fail; | |
224 | ||
225 | gpio->chip.label = client->name; | |
226 | ||
227 | gpio->client = client; | |
228 | i2c_set_clientdata(client, gpio); | |
229 | ||
230 | /* NOTE: these chips have strange "quasi-bidirectional" I/O pins. | |
231 | * We can't actually know whether a pin is configured (a) as output | |
232 | * and driving the signal low, or (b) as input and reporting a low | |
233 | * value ... without knowing the last value written since the chip | |
234 | * came out of reset (if any). We can't read the latched output. | |
235 | * | |
236 | * In short, the only reliable solution for setting up pin direction | |
237 | * is to do it explicitly. The setup() method can do that, but it | |
238 | * may cause transient glitching since it can't know the last value | |
239 | * written (some pins may need to be driven low). | |
240 | * | |
241 | * Using pdata->n_latch avoids that trouble. When left initialized | |
242 | * to zero, our software copy of the "latch" then matches the chip's | |
243 | * all-ones reset state. Otherwise it flags pins to be driven low. | |
244 | */ | |
245 | gpio->out = ~pdata->n_latch; | |
246 | ||
247 | status = gpiochip_add(&gpio->chip); | |
248 | if (status < 0) | |
249 | goto fail; | |
250 | ||
251 | /* NOTE: these chips can issue "some pin-changed" IRQs, which we | |
252 | * don't yet even try to use. Among other issues, the relevant | |
253 | * genirq state isn't available to modular drivers; and most irq | |
254 | * methods can't be called from sleeping contexts. | |
255 | */ | |
256 | ||
257 | dev_info(&client->dev, "gpios %d..%d on a %s%s\n", | |
258 | gpio->chip.base, | |
259 | gpio->chip.base + gpio->chip.ngpio - 1, | |
260 | client->name, | |
261 | client->irq ? " (irq ignored)" : ""); | |
262 | ||
263 | /* Let platform code set up the GPIOs and their users. | |
264 | * Now is the first time anyone could use them. | |
265 | */ | |
266 | if (pdata->setup) { | |
267 | status = pdata->setup(client, | |
268 | gpio->chip.base, gpio->chip.ngpio, | |
269 | pdata->context); | |
270 | if (status < 0) | |
271 | dev_warn(&client->dev, "setup --> %d\n", status); | |
272 | } | |
273 | ||
274 | return 0; | |
275 | ||
276 | fail: | |
277 | dev_dbg(&client->dev, "probe error %d for '%s'\n", | |
278 | status, client->name); | |
279 | kfree(gpio); | |
280 | return status; | |
281 | } | |
282 | ||
283 | static int pcf857x_remove(struct i2c_client *client) | |
284 | { | |
285 | struct pcf857x_platform_data *pdata = client->dev.platform_data; | |
286 | struct pcf857x *gpio = i2c_get_clientdata(client); | |
287 | int status = 0; | |
288 | ||
289 | if (pdata->teardown) { | |
290 | status = pdata->teardown(client, | |
291 | gpio->chip.base, gpio->chip.ngpio, | |
292 | pdata->context); | |
293 | if (status < 0) { | |
294 | dev_err(&client->dev, "%s --> %d\n", | |
295 | "teardown", status); | |
296 | return status; | |
297 | } | |
298 | } | |
299 | ||
300 | status = gpiochip_remove(&gpio->chip); | |
301 | if (status == 0) | |
302 | kfree(gpio); | |
303 | else | |
304 | dev_err(&client->dev, "%s --> %d\n", "remove", status); | |
305 | return status; | |
306 | } | |
307 | ||
308 | static struct i2c_driver pcf857x_driver = { | |
309 | .driver = { | |
310 | .name = "pcf857x", | |
311 | .owner = THIS_MODULE, | |
312 | }, | |
313 | .probe = pcf857x_probe, | |
314 | .remove = pcf857x_remove, | |
315 | }; | |
316 | ||
317 | static int __init pcf857x_init(void) | |
318 | { | |
319 | return i2c_add_driver(&pcf857x_driver); | |
320 | } | |
321 | module_init(pcf857x_init); | |
322 | ||
323 | static void __exit pcf857x_exit(void) | |
324 | { | |
325 | i2c_del_driver(&pcf857x_driver); | |
326 | } | |
327 | module_exit(pcf857x_exit); | |
328 | ||
329 | MODULE_LICENSE("GPL"); | |
330 | MODULE_AUTHOR("David Brownell"); |