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 /*
  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         gpio->chip.owner = THIS_MODULE;
 163
 164         /* NOTE:  the OnSemi jlc1562b is also largely compatible with
 165          * these parts, notably for output.  It has a low-resolution
 166          * DAC instead of pin change IRQs; and its inputs can be the
 167          * result of comparators.
 168          */
 169
 170         /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
 171          * 9670, 9672, 9764, and 9764a use quite a variety.
 172          *
 173          * NOTE: we don't distinguish here between *4 and *4a parts.
 174          */
 175         if (strcmp(client->name, "pcf8574") == 0
 176                         || strcmp(client->name, "pca8574") == 0
 177                         || strcmp(client->name, "pca9670") == 0
 178                         || strcmp(client->name, "pca9672") == 0
 179                         || strcmp(client->name, "pca9674") == 0
 180                         ) {
 181                 gpio->chip.ngpio = 8;
 182                 gpio->chip.direction_input = pcf857x_input8;
 183                 gpio->chip.get = pcf857x_get8;
 184                 gpio->chip.direction_output = pcf857x_output8;
 185                 gpio->chip.set = pcf857x_set8;
 186
 187                 if (!i2c_check_functionality(client->adapter,
 188                                 I2C_FUNC_SMBUS_BYTE))
 189                         status = -EIO;
 190
 191                 /* fail if there's no chip present */
 192                 else
 193                         status = i2c_smbus_read_byte(client);
 194
 195         /* '75/'75c addresses are 0x20..0x27, just like the '74;
 196          * the '75c doesn't have a current source pulling high.
 197          * 9671, 9673, and 9765 use quite a variety of addresses.
 198          *
 199          * NOTE: we don't distinguish here between '75 and '75c parts.
 200          */
 201         } else if (strcmp(client->name, "pcf8575") == 0
 202                         || strcmp(client->name, "pca8575") == 0
 203                         || strcmp(client->name, "pca9671") == 0
 204                         || strcmp(client->name, "pca9673") == 0
 205                         || strcmp(client->name, "pca9675") == 0
 206                         ) {
 207                 gpio->chip.ngpio = 16;
 208                 gpio->chip.direction_input = pcf857x_input16;
 209                 gpio->chip.get = pcf857x_get16;
 210                 gpio->chip.direction_output = pcf857x_output16;
 211                 gpio->chip.set = pcf857x_set16;
 212
 213                 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 214                         status = -EIO;
 215
 216                 /* fail if there's no chip present */
 217                 else
 218                         status = i2c_read_le16(client);
 219
 220         } else
 221                 status = -ENODEV;
 222
 223         if (status < 0)
 224                 goto fail;
 225
 226         gpio->chip.label = client->name;
 227
 228         gpio->client = client;
 229         i2c_set_clientdata(client, gpio);
 230
 231         /* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
 232          * We can't actually know whether a pin is configured (a) as output
 233          * and driving the signal low, or (b) as input and reporting a low
 234          * value ... without knowing the last value written since the chip
 235          * came out of reset (if any).  We can't read the latched output.
 236          *
 237          * In short, the only reliable solution for setting up pin direction
 238          * is to do it explicitly.  The setup() method can do that, but it
 239          * may cause transient glitching since it can't know the last value
 240          * written (some pins may need to be driven low).
 241          *
 242          * Using pdata->n_latch avoids that trouble.  When left initialized
 243          * to zero, our software copy of the "latch" then matches the chip's
 244          * all-ones reset state.  Otherwise it flags pins to be driven low.
 245          */
 246         gpio->out = ~pdata->n_latch;
 247
 248         status = gpiochip_add(&gpio->chip);
 249         if (status < 0)
 250                 goto fail;
 251
 252         /* NOTE: these chips can issue "some pin-changed" IRQs, which we
 253          * don't yet even try to use.  Among other issues, the relevant
 254          * genirq state isn't available to modular drivers; and most irq
 255          * methods can't be called from sleeping contexts.
 256          */
 257
 258         dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
 259                         gpio->chip.base,
 260                         gpio->chip.base + gpio->chip.ngpio - 1,
 261                         client->name,
 262                         client->irq ? " (irq ignored)" : "");
 263
 264         /* Let platform code set up the GPIOs and their users.
 265          * Now is the first time anyone could use them.
 266          */
 267         if (pdata->setup) {
 268                 status = pdata->setup(client,
 269                                 gpio->chip.base, gpio->chip.ngpio,
 270                                 pdata->context);
 271                 if (status < 0)
 272                         dev_warn(&client->dev, "setup --> %d\n", status);
 273         }
 274
 275         return 0;
 276
 277 fail:
 278         dev_dbg(&client->dev, "probe error %d for '%s'\n",
 279                         status, client->name);
 280         kfree(gpio);
 281         return status;
 282 }
 283
 284 static int pcf857x_remove(struct i2c_client *client)
 285 {
 286         struct pcf857x_platform_data    *pdata = client->dev.platform_data;
 287         struct pcf857x                  *gpio = i2c_get_clientdata(client);
 288         int                             status = 0;
 289
 290         if (pdata->teardown) {
 291                 status = pdata->teardown(client,
 292                                 gpio->chip.base, gpio->chip.ngpio,
 293                                 pdata->context);
 294                 if (status < 0) {
 295                         dev_err(&client->dev, "%s --> %d\n",
 296                                         "teardown", status);
 297                         return status;
 298                 }
 299         }
 300
 301         status = gpiochip_remove(&gpio->chip);
 302         if (status == 0)
 303                 kfree(gpio);
 304         else
 305                 dev_err(&client->dev, "%s --> %d\n", "remove", status);
 306         return status;
 307 }
 308
 309 static struct i2c_driver pcf857x_driver = {
 310         .driver = {
 311                 .name   = "pcf857x",
 312                 .owner  = THIS_MODULE,
 313         },
 314         .probe  = pcf857x_probe,
 315         .remove = pcf857x_remove,
 316 };
 317
 318 static int __init pcf857x_init(void)
 319 {
 320         return i2c_add_driver(&pcf857x_driver);
 321 }
 322 module_init(pcf857x_init);
 323
 324 static void __exit pcf857x_exit(void)
 325 {
 326         i2c_del_driver(&pcf857x_driver);
 327 }
 328 module_exit(pcf857x_exit);
 329
 330 MODULE_LICENSE("GPL");
 331 MODULE_AUTHOR("David Brownell");