drivers/gpio/pcf857x.c

   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 static const struct i2c_device_id pcf857x_id[] = {
  30         { "pcf8574", 8 },
  31         { "pca8574", 8 },
  32         { "pca9670", 8 },
  33         { "pca9672", 8 },
  34         { "pca9674", 8 },
  35         { "pcf8575", 16 },
  36         { "pca8575", 16 },
  37         { "pca9671", 16 },
  38         { "pca9673", 16 },
  39         { "pca9675", 16 },
  40         { }
  41 };
  42 MODULE_DEVICE_TABLE(i2c, pcf857x_id);
  43
  44 /*
  45  * The pcf857x, pca857x, and pca967x chips only expose one read and one
  46  * write register.  Writing a "one" bit (to match the reset state) lets
  47  * that pin be used as an input; it's not an open-drain model, but acts
  48  * a bit like one.  This is described as "quasi-bidirectional"; read the
  49  * chip documentation for details.
  50  *
  51  * Many other I2C GPIO expander chips (like the pca953x models) have
  52  * more complex register models and more conventional circuitry using
  53  * push/pull drivers.  They often use the same 0x20..0x27 addresses as
  54  * pcf857x parts, making the "legacy" I2C driver model problematic.
  55  */
  56 struct pcf857x {
  57         struct gpio_chip        chip;
  58         struct i2c_client       *client;
  59         unsigned                out;            /* software latch */
  60 };
  61
  62 /*-------------------------------------------------------------------------*/
  63
  64 /* Talk to 8-bit I/O expander */
  65
  66 static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
  67 {
  68         struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
  69
  70         gpio->out |= (1 << offset);
  71         return i2c_smbus_write_byte(gpio->client, gpio->out);
  72 }
  73
  74 static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
  75 {
  76         struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
  77         s32             value;
  78
  79         value = i2c_smbus_read_byte(gpio->client);
  80         return (value < 0) ? 0 : (value & (1 << offset));
  81 }
  82
  83 static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
  84 {
  85         struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
  86         unsigned        bit = 1 << offset;
  87
  88         if (value)
  89                 gpio->out |= bit;
  90         else
  91                 gpio->out &= ~bit;
  92         return i2c_smbus_write_byte(gpio->client, gpio->out);
  93 }
  94
  95 static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
  96 {
  97         pcf857x_output8(chip, offset, value);
  98 }
  99
 100 /*-------------------------------------------------------------------------*/
 101
 102 /* Talk to 16-bit I/O expander */
 103
 104 static int i2c_write_le16(struct i2c_client *client, u16 word)
 105 {
 106         u8 buf[2] = { word & 0xff, word >> 8, };
 107         int status;
 108
 109         status = i2c_master_send(client, buf, 2);
 110         return (status < 0) ? status : 0;
 111 }
 112
 113 static int i2c_read_le16(struct i2c_client *client)
 114 {
 115         u8 buf[2];
 116         int status;
 117
 118         status = i2c_master_recv(client, buf, 2);
 119         if (status < 0)
 120                 return status;
 121         return (buf[1] << 8) | buf[0];
 122 }
 123
 124 static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
 125 {
 126         struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 127
 128         gpio->out |= (1 << offset);
 129         return i2c_write_le16(gpio->client, gpio->out);
 130 }
 131
 132 static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
 133 {
 134         struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 135         int             value;
 136
 137         value = i2c_read_le16(gpio->client);
 138         return (value < 0) ? 0 : (value & (1 << offset));
 139 }
 140
 141 static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
 142 {
 143         struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 144         unsigned        bit = 1 << offset;
 145
 146         if (value)
 147                 gpio->out |= bit;
 148         else
 149                 gpio->out &= ~bit;
 150         return i2c_write_le16(gpio->client, gpio->out);
 151 }
 152
 153 static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
 154 {
 155         pcf857x_output16(chip, offset, value);
 156 }
 157
 158 /*-------------------------------------------------------------------------*/
 159
 160 static int pcf857x_probe(struct i2c_client *client,
 161                          const struct i2c_device_id *id)
 162 {
 163         struct pcf857x_platform_data    *pdata;
 164         struct pcf857x                  *gpio;
 165         int                             status;
 166
 167         pdata = client->dev.platform_data;
 168         if (!pdata)
 169                 return -ENODEV;
 170
 171         /* Allocate, initialize, and register this gpio_chip. */
 172         gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
 173         if (!gpio)
 174                 return -ENOMEM;
 175
 176         gpio->chip.base = pdata->gpio_base;
 177         gpio->chip.can_sleep = 1;
 178         gpio->chip.owner = THIS_MODULE;
 179
 180         /* NOTE:  the OnSemi jlc1562b is also largely compatible with
 181          * these parts, notably for output.  It has a low-resolution
 182          * DAC instead of pin change IRQs; and its inputs can be the
 183          * result of comparators.
 184          */
 185
 186         /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
 187          * 9670, 9672, 9764, and 9764a use quite a variety.
 188          *
 189          * NOTE: we don't distinguish here between *4 and *4a parts.
 190          */
 191         gpio->chip.ngpio = id->driver_data;
 192         if (gpio->chip.ngpio == 8) {
 193                 gpio->chip.direction_input = pcf857x_input8;
 194                 gpio->chip.get = pcf857x_get8;
 195                 gpio->chip.direction_output = pcf857x_output8;
 196                 gpio->chip.set = pcf857x_set8;
 197
 198                 if (!i2c_check_functionality(client->adapter,
 199                                 I2C_FUNC_SMBUS_BYTE))
 200                         status = -EIO;
 201
 202                 /* fail if there's no chip present */
 203                 else
 204                         status = i2c_smbus_read_byte(client);
 205
 206         /* '75/'75c addresses are 0x20..0x27, just like the '74;
 207          * the '75c doesn't have a current source pulling high.
 208          * 9671, 9673, and 9765 use quite a variety of addresses.
 209          *
 210          * NOTE: we don't distinguish here between '75 and '75c parts.
 211          */
 212         } else if (gpio->chip.ngpio == 16) {
 213                 gpio->chip.direction_input = pcf857x_input16;
 214                 gpio->chip.get = pcf857x_get16;
 215                 gpio->chip.direction_output = pcf857x_output16;
 216                 gpio->chip.set = pcf857x_set16;
 217
 218                 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 219                         status = -EIO;
 220
 221                 /* fail if there's no chip present */
 222                 else
 223                         status = i2c_read_le16(client);
 224
 225         } else
 226                 status = -ENODEV;
 227
 228         if (status < 0)
 229                 goto fail;
 230
 231         gpio->chip.label = client->name;
 232
 233         gpio->client = client;
 234         i2c_set_clientdata(client, gpio);
 235
 236         /* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
 237          * We can't actually know whether a pin is configured (a) as output
 238          * and driving the signal low, or (b) as input and reporting a low
 239          * value ... without knowing the last value written since the chip
 240          * came out of reset (if any).  We can't read the latched output.
 241          *
 242          * In short, the only reliable solution for setting up pin direction
 243          * is to do it explicitly.  The setup() method can do that, but it
 244          * may cause transient glitching since it can't know the last value
 245          * written (some pins may need to be driven low).
 246          *
 247          * Using pdata->n_latch avoids that trouble.  When left initialized
 248          * to zero, our software copy of the "latch" then matches the chip's
 249          * all-ones reset state.  Otherwise it flags pins to be driven low.
 250          */
 251         gpio->out = ~pdata->n_latch;
 252
 253         status = gpiochip_add(&gpio->chip);
 254         if (status < 0)
 255                 goto fail;
 256
 257         /* NOTE: these chips can issue "some pin-changed" IRQs, which we
 258          * don't yet even try to use.  Among other issues, the relevant
 259          * genirq state isn't available to modular drivers; and most irq
 260          * methods can't be called from sleeping contexts.
 261          */
 262
 263         dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
 264                         gpio->chip.base,
 265                         gpio->chip.base + gpio->chip.ngpio - 1,
 266                         client->name,
 267                         client->irq ? " (irq ignored)" : "");
 268
 269         /* Let platform code set up the GPIOs and their users.
 270          * Now is the first time anyone could use them.
 271          */
 272         if (pdata->setup) {
 273                 status = pdata->setup(client,
 274                                 gpio->chip.base, gpio->chip.ngpio,
 275                                 pdata->context);
 276                 if (status < 0)
 277                         dev_warn(&client->dev, "setup --> %d\n", status);
 278         }
 279
 280         return 0;
 281
 282 fail:
 283         dev_dbg(&client->dev, "probe error %d for '%s'\n",
 284                         status, client->name);
 285         kfree(gpio);
 286         return status;
 287 }
 288
 289 static int pcf857x_remove(struct i2c_client *client)
 290 {
 291         struct pcf857x_platform_data    *pdata = client->dev.platform_data;
 292         struct pcf857x                  *gpio = i2c_get_clientdata(client);
 293         int                             status = 0;
 294
 295         if (pdata->teardown) {
 296                 status = pdata->teardown(client,
 297                                 gpio->chip.base, gpio->chip.ngpio,
 298                                 pdata->context);
 299                 if (status < 0) {
 300                         dev_err(&client->dev, "%s --> %d\n",
 301                                         "teardown", status);
 302                         return status;
 303                 }
 304         }
 305
 306         status = gpiochip_remove(&gpio->chip);
 307         if (status == 0)
 308                 kfree(gpio);
 309         else
 310                 dev_err(&client->dev, "%s --> %d\n", "remove", status);
 311         return status;
 312 }
 313
 314 static struct i2c_driver pcf857x_driver = {
 315         .driver = {
 316                 .name   = "pcf857x",
 317                 .owner  = THIS_MODULE,
 318         },
 319         .probe  = pcf857x_probe,
 320         .remove = pcf857x_remove,
 321         .id_table = pcf857x_id,
 322 };
 323
 324 static int __init pcf857x_init(void)
 325 {
 326         return i2c_add_driver(&pcf857x_driver);
 327 }
 328 module_init(pcf857x_init);
 329
 330 static void __exit pcf857x_exit(void)
 331 {
 332         i2c_del_driver(&pcf857x_driver);
 333 }
 334 module_exit(pcf857x_exit);
 335
 336 MODULE_LICENSE("GPL");
 337 MODULE_AUTHOR("David Brownell");