drivers/gpio/gpio-pcf857x.c

   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");