1 /* 2 * 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/gpio.h> 24 #include <linux/i2c.h> 25 #include <linux/i2c/pcf857x.h> 26 #include <linux/module.h> 27 28 29 static const struct i2c_device_id pcf857x_id[] = { 30 { "pcf8574", 8 }, 31 { "pcf8574a", 8 }, 32 { "pca8574", 8 }, 33 { "pca9670", 8 }, 34 { "pca9672", 8 }, 35 { "pca9674", 8 }, 36 { "pcf8575", 16 }, 37 { "pca8575", 16 }, 38 { "pca9671", 16 }, 39 { "pca9673", 16 }, 40 { "pca9675", 16 }, 41 { "max7328", 8 }, 42 { "max7329", 8 }, 43 { } 44 }; 45 MODULE_DEVICE_TABLE(i2c, pcf857x_id); 46 47 /* 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. 53 * 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. 58 */ 59 struct pcf857x { 60 struct gpio_chip chip; 61 struct i2c_client *client; 62 struct mutex lock; /* protect 'out' */ 63 unsigned out; /* software latch */ 64 65 int (*write)(struct i2c_client *client, unsigned data); 66 int (*read)(struct i2c_client *client); 67 }; 68 69 /*-------------------------------------------------------------------------*/ 70 71 /* Talk to 8-bit I/O expander */ 72 73 static int i2c_write_le8(struct i2c_client *client, unsigned data) 74 { 75 return i2c_smbus_write_byte(client, data); 76 } 77 78 static int i2c_read_le8(struct i2c_client *client) 79 { 80 return (int)i2c_smbus_read_byte(client); 81 } 82 83 /* Talk to 16-bit I/O expander */ 84 85 static int i2c_write_le16(struct i2c_client *client, unsigned word) 86 { 87 u8 buf[2] = { word & 0xff, word >> 8, }; 88 int status; 89 90 status = i2c_master_send(client, buf, 2); 91 return (status < 0) ? status : 0; 92 } 93 94 static int i2c_read_le16(struct i2c_client *client) 95 { 96 u8 buf[2]; 97 int status; 98 99 status = i2c_master_recv(client, buf, 2); 100 if (status < 0) 101 return status; 102 return (buf[1] << 8) | buf[0]; 103 } 104 105 /*-------------------------------------------------------------------------*/ 106 107 static int pcf857x_input(struct gpio_chip *chip, unsigned offset) 108 { 109 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); 110 int status; 111 112 mutex_lock(&gpio->lock); 113 gpio->out |= (1 << offset); 114 status = gpio->write(gpio->client, gpio->out); 115 mutex_unlock(&gpio->lock); 116 117 return status; 118 } 119 120 static int pcf857x_get(struct gpio_chip *chip, unsigned offset) 121 { 122 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); 123 int value; 124 125 value = gpio->read(gpio->client); 126 return (value < 0) ? 0 : (value & (1 << offset)); 127 } 128 129 static int pcf857x_output(struct gpio_chip *chip, unsigned offset, int value) 130 { 131 struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); 132 unsigned bit = 1 << offset; 133 int status; 134 135 mutex_lock(&gpio->lock); 136 if (value) 137 gpio->out |= bit; 138 else 139 gpio->out &= ~bit; 140 status = gpio->write(gpio->client, gpio->out); 141 mutex_unlock(&gpio->lock); 142 143 return status; 144 } 145 146 static void pcf857x_set(struct gpio_chip *chip, unsigned offset, int value) 147 { 148 pcf857x_output(chip, offset, value); 149 } 150 151 /*-------------------------------------------------------------------------*/ 152 153 static int pcf857x_probe(struct i2c_client *client, 154 const struct i2c_device_id *id) 155 { 156 struct pcf857x_platform_data *pdata; 157 struct pcf857x *gpio; 158 int status; 159 160 pdata = client->dev.platform_data; 161 if (!pdata) { 162 dev_dbg(&client->dev, "no platform data\n"); 163 } 164 165 /* Allocate, initialize, and register this gpio_chip. */ 166 gpio = kzalloc(sizeof *gpio, GFP_KERNEL); 167 if (!gpio) 168 return -ENOMEM; 169 170 mutex_init(&gpio->lock); 171 172 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; 181 182 /* 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. 186 */ 187 188 /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f; 189 * 9670, 9672, 9764, and 9764a use quite a variety. 190 * 191 * NOTE: we don't distinguish here between *4 and *4a parts. 192 */ 193 if (gpio->chip.ngpio == 8) { 194 gpio->write = i2c_write_le8; 195 gpio->read = i2c_read_le8; 196 197 if (!i2c_check_functionality(client->adapter, 198 I2C_FUNC_SMBUS_BYTE)) 199 status = -EIO; 200 201 /* fail if there's no chip present */ 202 else 203 status = i2c_smbus_read_byte(client); 204 205 /* '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. 208 * 209 * NOTE: we don't distinguish here between '75 and '75c parts. 210 */ 211 } else if (gpio->chip.ngpio == 16) { 212 gpio->write = i2c_write_le16; 213 gpio->read = i2c_read_le16; 214 215 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 216 status = -EIO; 217 218 /* fail if there's no chip present */ 219 else 220 status = i2c_read_le16(client); 221 222 } else { 223 dev_dbg(&client->dev, "unsupported number of gpios\n"); 224 status = -EINVAL; 225 } 226 227 if (status < 0) 228 goto fail; 229 230 gpio->chip.label = client->name; 231 232 gpio->client = client; 233 i2c_set_clientdata(client, gpio); 234 235 /* 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. 240 * 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). 245 * 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. 249 */ 250 gpio->out = pdata ? ~pdata->n_latch : ~0; 251 252 status = gpiochip_add(&gpio->chip); 253 if (status < 0) 254 goto fail; 255 256 /* 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. 260 */ 261 262 dev_info(&client->dev, "%s\n", 263 client->irq ? " (irq ignored)" : ""); 264 265 /* Let platform code set up the GPIOs and their users. 266 * Now is the first time anyone could use them. 267 */ 268 if (pdata && pdata->setup) { 269 status = pdata->setup(client, 270 gpio->chip.base, gpio->chip.ngpio, 271 pdata->context); 272 if (status < 0) 273 dev_warn(&client->dev, "setup --> %d\n", status); 274 } 275 276 return 0; 277 278 fail: 279 dev_dbg(&client->dev, "probe error %d for '%s'\n", 280 status, client->name); 281 kfree(gpio); 282 return status; 283 } 284 285 static int pcf857x_remove(struct i2c_client *client) 286 { 287 struct pcf857x_platform_data *pdata = client->dev.platform_data; 288 struct pcf857x *gpio = i2c_get_clientdata(client); 289 int status = 0; 290 291 if (pdata && pdata->teardown) { 292 status = pdata->teardown(client, 293 gpio->chip.base, gpio->chip.ngpio, 294 pdata->context); 295 if (status < 0) { 296 dev_err(&client->dev, "%s --> %d\n", 297 "teardown", status); 298 return status; 299 } 300 } 301 302 status = gpiochip_remove(&gpio->chip); 303 if (status == 0) 304 kfree(gpio); 305 else 306 dev_err(&client->dev, "%s --> %d\n", "remove", status); 307 return status; 308 } 309 310 static struct i2c_driver pcf857x_driver = { 311 .driver = { 312 .name = "pcf857x", 313 .owner = THIS_MODULE, 314 }, 315 .probe = pcf857x_probe, 316 .remove = pcf857x_remove, 317 .id_table = pcf857x_id, 318 }; 319 320 static int __init pcf857x_init(void) 321 { 322 return i2c_add_driver(&pcf857x_driver); 323 } 324 /* register after i2c postcore initcall and before 325 * subsys initcalls that may rely on these GPIOs 326 */ 327 subsys_initcall(pcf857x_init); 328 329 static void __exit pcf857x_exit(void) 330 { 331 i2c_del_driver(&pcf857x_driver); 332 } 333 module_exit(pcf857x_exit); 334 335 MODULE_LICENSE("GPL"); 336 MODULE_AUTHOR("David Brownell"); 337