i2c-mux-gpio.c

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/*
 * I2C multiplexer using GPIO API
 *
 * Peter Korsgaard <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/i2c-mux-gpio.h>
#include <linux/platform_device.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/gpio.h>

struct gpiomux {
    struct i2c_adapter *parent;
    struct i2c_adapter **adap; /* child busses */
    struct i2c_mux_gpio_platform_data data;
    unsigned gpio_base;
};

static void i2c_mux_gpio_set(const struct gpiomux *mux, unsigned val)
{
    int i;

    for (i = 0; i < mux->data.n_gpios; i++)
        gpio_set_value(mux->gpio_base + mux->data.gpios[i],
                   val & (1 << i));
}

static int i2c_mux_gpio_select(struct i2c_adapter *adap, void *data, u32 chan)
{
    struct gpiomux *mux = data;

    i2c_mux_gpio_set(mux, mux->data.values[chan]);

    return 0;
}

static int i2c_mux_gpio_deselect(struct i2c_adapter *adap, void *data, u32 chan)
{
    struct gpiomux *mux = data;

    i2c_mux_gpio_set(mux, mux->data.idle);

    return 0;
}

static int __devinit match_gpio_chip_by_label(struct gpio_chip *chip,
                          void *data)
{
    return !strcmp(chip->label, data);
}

static int __devinit i2c_mux_gpio_probe(struct platform_device *pdev)
{
    struct gpiomux *mux;
    struct i2c_mux_gpio_platform_data *pdata;
    struct i2c_adapter *parent;
    int (*deselect) (struct i2c_adapter *, void *, u32);
    unsigned initial_state, gpio_base;
    int i, ret;

    pdata = pdev->dev.platform_data;
    if (!pdata) {
        dev_err(&pdev->dev, "Missing platform data\n");
        return -ENODEV;
    }

    /*
     * If a GPIO chip name is provided, the GPIO pin numbers provided are
     * relative to its base GPIO number. Otherwise they are absolute.
     */
    if (pdata->gpio_chip) {
        struct gpio_chip *gpio;

        gpio = gpiochip_find(pdata->gpio_chip,
                     match_gpio_chip_by_label);
        if (!gpio)
            return -EPROBE_DEFER;

        gpio_base = gpio->base;
    } else {
        gpio_base = 0;
    }

    parent = i2c_get_adapter(pdata->parent);
    if (!parent) {
        dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
            pdata->parent);
        return -ENODEV;
    }

    mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
    if (!mux) {
        ret = -ENOMEM;
        goto alloc_failed;
    }

    mux->parent = parent;
    mux->data = *pdata;
    mux->gpio_base = gpio_base;
    mux->adap = devm_kzalloc(&pdev->dev,
                 sizeof(*mux->adap) * pdata->n_values,
                 GFP_KERNEL);
    if (!mux->adap) {
        ret = -ENOMEM;
        goto alloc_failed;
    }

    if (pdata->idle != I2C_MUX_GPIO_NO_IDLE) {
        initial_state = pdata->idle;
        deselect = i2c_mux_gpio_deselect;
    } else {
        initial_state = pdata->values[0];
        deselect = NULL;
    }

    for (i = 0; i < pdata->n_gpios; i++) {
        ret = gpio_request(gpio_base + pdata->gpios[i], "i2c-mux-gpio");
        if (ret)
            goto err_request_gpio;
        gpio_direction_output(gpio_base + pdata->gpios[i],
                      initial_state & (1 << i));
    }

    for (i = 0; i < pdata->n_values; i++) {
        u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0;
        unsigned int class = pdata->classes ? pdata->classes[i] : 0;

        mux->adap[i] = i2c_add_mux_adapter(parent, &pdev->dev, mux, nr,
                           i, class,
                           i2c_mux_gpio_select, deselect);
        if (!mux->adap[i]) {
            ret = -ENODEV;
            dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
            goto add_adapter_failed;
        }
    }

    dev_info(&pdev->dev, "%d port mux on %s adapter\n",
         pdata->n_values, parent->name);

    platform_set_drvdata(pdev, mux);

    return 0;

add_adapter_failed:
    for (; i > 0; i--)
        i2c_del_mux_adapter(mux->adap[i - 1]);
    i = pdata->n_gpios;
err_request_gpio:
    for (; i > 0; i--)
        gpio_free(gpio_base + pdata->gpios[i - 1]);
alloc_failed:
    i2c_put_adapter(parent);

    return ret;
}

static int __devexit i2c_mux_gpio_remove(struct platform_device *pdev)
{
    struct gpiomux *mux = platform_get_drvdata(pdev);
    int i;

    for (i = 0; i < mux->data.n_values; i++)
        i2c_del_mux_adapter(mux->adap[i]);

    for (i = 0; i < mux->data.n_gpios; i++)
        gpio_free(mux->gpio_base + mux->data.gpios[i]);

    platform_set_drvdata(pdev, NULL);
    i2c_put_adapter(mux->parent);

    return 0;
}

static struct platform_driver i2c_mux_gpio_driver = {
    .probe  = i2c_mux_gpio_probe,
    .remove = __devexit_p(i2c_mux_gpio_remove),
    .driver = {
        .owner  = THIS_MODULE,
        .name   = "i2c-mux-gpio",
    },
};

module_platform_driver(i2c_mux_gpio_driver);

MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
MODULE_AUTHOR("Peter Korsgaard <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:i2c-mux-gpio");