drivers/i2c/muxes/gpio-i2cmux.c

   1 /*
   2  * I2C multiplexer using GPIO API
   3  *
   4  * Peter Korsgaard <peter.korsgaard@barco.com>
   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 version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/i2c.h>
  12 #include <linux/i2c-mux.h>
  13 #include <linux/gpio-i2cmux.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/init.h>
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include <linux/gpio.h>
  19
  20 struct gpiomux {
  21         struct i2c_adapter *parent;
  22         struct i2c_adapter **adap; /* child busses */
  23         struct gpio_i2cmux_platform_data data;
  24 };
  25
  26 static void gpiomux_set(const struct gpiomux *mux, unsigned val)
  27 {
  28         int i;
  29
  30         for (i = 0; i < mux->data.n_gpios; i++)
  31                 gpio_set_value(mux->data.gpios[i], val & (1 << i));
  32 }
  33
  34 static int gpiomux_select(struct i2c_adapter *adap, void *data, u32 chan)
  35 {
  36         struct gpiomux *mux = data;
  37
  38         gpiomux_set(mux, mux->data.values[chan]);
  39
  40         return 0;
  41 }
  42
  43 static int gpiomux_deselect(struct i2c_adapter *adap, void *data, u32 chan)
  44 {
  45         struct gpiomux *mux = data;
  46
  47         gpiomux_set(mux, mux->data.idle);
  48
  49         return 0;
  50 }
  51
  52 static int __devinit gpiomux_probe(struct platform_device *pdev)
  53 {
  54         struct gpiomux *mux;
  55         struct gpio_i2cmux_platform_data *pdata;
  56         struct i2c_adapter *parent;
  57         int (*deselect) (struct i2c_adapter *, void *, u32);
  58         unsigned initial_state;
  59         int i, ret;
  60
  61         pdata = pdev->dev.platform_data;
  62         if (!pdata) {
  63                 dev_err(&pdev->dev, "Missing platform data\n");
  64                 return -ENODEV;
  65         }
  66
  67         parent = i2c_get_adapter(pdata->parent);
  68         if (!parent) {
  69                 dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
  70                         pdata->parent);
  71                 return -ENODEV;
  72         }
  73
  74         mux = kzalloc(sizeof(*mux), GFP_KERNEL);
  75         if (!mux) {
  76                 ret = -ENOMEM;
  77                 goto alloc_failed;
  78         }
  79
  80         mux->parent = parent;
  81         mux->data = *pdata;
  82         mux->adap = kzalloc(sizeof(struct i2c_adapter *) * pdata->n_values,
  83                             GFP_KERNEL);
  84         if (!mux->adap) {
  85                 ret = -ENOMEM;
  86                 goto alloc_failed2;
  87         }
  88
  89         if (pdata->idle != GPIO_I2CMUX_NO_IDLE) {
  90                 initial_state = pdata->idle;
  91                 deselect = gpiomux_deselect;
  92         } else {
  93                 initial_state = pdata->values[0];
  94                 deselect = NULL;
  95         }
  96
  97         for (i = 0; i < pdata->n_gpios; i++) {
  98                 ret = gpio_request(pdata->gpios[i], "gpio-i2cmux");
  99                 if (ret)
 100                         goto err_request_gpio;
 101                 gpio_direction_output(pdata->gpios[i],
 102                                       initial_state & (1 << i));
 103         }
 104
 105         for (i = 0; i < pdata->n_values; i++) {
 106                 u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0;
 107
 108                 mux->adap[i] = i2c_add_mux_adapter(parent, mux, nr, i,
 109                                                    gpiomux_select, deselect);
 110                 if (!mux->adap[i]) {
 111                         ret = -ENODEV;
 112                         dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
 113                         goto add_adapter_failed;
 114                 }
 115         }
 116
 117         dev_info(&pdev->dev, "%d port mux on %s adapter\n",
 118                  pdata->n_values, parent->name);
 119
 120         platform_set_drvdata(pdev, mux);
 121
 122         return 0;
 123
 124 add_adapter_failed:
 125         for (; i > 0; i--)
 126                 i2c_del_mux_adapter(mux->adap[i - 1]);
 127         i = pdata->n_gpios;
 128 err_request_gpio:
 129         for (; i > 0; i--)
 130                 gpio_free(pdata->gpios[i - 1]);
 131         kfree(mux->adap);
 132 alloc_failed2:
 133         kfree(mux);
 134 alloc_failed:
 135         i2c_put_adapter(parent);
 136
 137         return ret;
 138 }
 139
 140 static int __devexit gpiomux_remove(struct platform_device *pdev)
 141 {
 142         struct gpiomux *mux = platform_get_drvdata(pdev);
 143         int i;
 144
 145         for (i = 0; i < mux->data.n_values; i++)
 146                 i2c_del_mux_adapter(mux->adap[i]);
 147
 148         for (i = 0; i < mux->data.n_gpios; i++)
 149                 gpio_free(mux->data.gpios[i]);
 150
 151         platform_set_drvdata(pdev, NULL);
 152         i2c_put_adapter(mux->parent);
 153         kfree(mux->adap);
 154         kfree(mux);
 155
 156         return 0;
 157 }
 158
 159 static struct platform_driver gpiomux_driver = {
 160         .probe  = gpiomux_probe,
 161         .remove = __devexit_p(gpiomux_remove),
 162         .driver = {
 163                 .owner  = THIS_MODULE,
 164                 .name   = "gpio-i2cmux",
 165         },
 166 };
 167
 168 module_platform_driver(gpiomux_driver);
 169
 170 MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
 171 MODULE_AUTHOR("Peter Korsgaard <peter.korsgaard@barco.com>");
 172 MODULE_LICENSE("GPL");
 173 MODULE_ALIAS("platform:gpio-i2cmux");