i2c-mux-pca954x.c

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/*
 * I2C multiplexer
 *
 * Copyright (c) 2008-2009 Rodolfo Giometti <[email protected]>
 * Copyright (c) 2008-2009 Eurotech S.p.A. <[email protected]>
 *
 * This module supports the PCA954x series of I2C multiplexer/switch chips
 * made by Philips Semiconductors.
 * This includes the:
 *   PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
 *   and PCA9548.
 *
 * These chips are all controlled via the I2C bus itself, and all have a
 * single 8-bit register. The upstream "parent" bus fans out to two,
 * four, or eight downstream busses or channels; which of these
 * are selected is determined by the chip type and register contents. A
 * mux can select only one sub-bus at a time; a switch can select any
 * combination simultaneously.
 *
 * Based on:
 *  pca954x.c from Kumar Gala <[email protected]>
 * Copyright (C) 2006
 *
 * Based on:
 *  pca954x.c from Ken Harrenstien
 * Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
 *
 * Based on:
 *  i2c-virtual_cb.c from Brian Kuschak <[email protected]>
 * and
 *  pca9540.c from Jean Delvare <[email protected]>.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

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

#include <linux/i2c/pca954x.h>

#define PCA954X_MAX_NCHANS 8

enum pca_type {
    pca_9540,
    pca_9542,
    pca_9543,
    pca_9544,
    pca_9545,
    pca_9546,
    pca_9547,
    pca_9548,
};

struct pca954x {
    enum pca_type type;
    struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];

    u8 last_chan;       /* last register value */
};

struct chip_desc {
    u8 nchans;
    u8 enable;  /* used for muxes only */
    enum muxtype {
        pca954x_ismux = 0,
        pca954x_isswi
    } muxtype;
};

/* Provide specs for the PCA954x types we know about */
static const struct chip_desc chips[] = {
    [pca_9540] = {
        .nchans = 2,
        .enable = 0x4,
        .muxtype = pca954x_ismux,
    },
    [pca_9543] = {
        .nchans = 2,
        .muxtype = pca954x_isswi,
    },
    [pca_9544] = {
        .nchans = 4,
        .enable = 0x4,
        .muxtype = pca954x_ismux,
    },
    [pca_9545] = {
        .nchans = 4,
        .muxtype = pca954x_isswi,
    },
    [pca_9547] = {
        .nchans = 8,
        .enable = 0x8,
        .muxtype = pca954x_ismux,
    },
    [pca_9548] = {
        .nchans = 8,
        .muxtype = pca954x_isswi,
    },
};

static const struct i2c_device_id pca954x_id[] = {
    { "pca9540", pca_9540 },
    { "pca9542", pca_9540 },
    { "pca9543", pca_9543 },
    { "pca9544", pca_9544 },
    { "pca9545", pca_9545 },
    { "pca9546", pca_9545 },
    { "pca9547", pca_9547 },
    { "pca9548", pca_9548 },
    { }
};
MODULE_DEVICE_TABLE(i2c, pca954x_id);

/* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
   for this as they will try to lock adapter a second time */
static int pca954x_reg_write(struct i2c_adapter *adap,
                 struct i2c_client *client, u8 val)
{
    int ret = -ENODEV;

    if (adap->algo->master_xfer) {
        struct i2c_msg msg;
        char buf[1];

        msg.addr = client->addr;
        msg.flags = 0;
        msg.len = 1;
        buf[0] = val;
        msg.buf = buf;
        ret = adap->algo->master_xfer(adap, &msg, 1);
    } else {
        union i2c_smbus_data data;
        ret = adap->algo->smbus_xfer(adap, client->addr,
                         client->flags,
                         I2C_SMBUS_WRITE,
                         val, I2C_SMBUS_BYTE, &data);
    }

    return ret;
}

static int pca954x_select_chan(struct i2c_adapter *adap,
                   void *client, u32 chan)
{
    struct pca954x *data = i2c_get_clientdata(client);
    const struct chip_desc *chip = &chips[data->type];
    u8 regval;
    int ret = 0;

    /* we make switches look like muxes, not sure how to be smarter */
    if (chip->muxtype == pca954x_ismux)
        regval = chan | chip->enable;
    else
        regval = 1 << chan;

    /* Only select the channel if its different from the last channel */
    if (data->last_chan != regval) {
        ret = pca954x_reg_write(adap, client, regval);
        data->last_chan = regval;
    }

    return ret;
}

static int pca954x_deselect_mux(struct i2c_adapter *adap,
                void *client, u32 chan)
{
    struct pca954x *data = i2c_get_clientdata(client);

    /* Deselect active channel */
    data->last_chan = 0;
    return pca954x_reg_write(adap, client, data->last_chan);
}

/*
 * I2C init/probing/exit functions
 */
static int pca954x_probe(struct i2c_client *client,
             const struct i2c_device_id *id)
{
    struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
    struct pca954x_platform_data *pdata = client->dev.platform_data;
    int num, force, class;
    struct pca954x *data;
    int ret = -ENODEV;

    if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
        goto err;

    data = kzalloc(sizeof(struct pca954x), GFP_KERNEL);
    if (!data) {
        ret = -ENOMEM;
        goto err;
    }

    i2c_set_clientdata(client, data);

    /* Write the mux register at addr to verify
     * that the mux is in fact present. This also
     * initializes the mux to disconnected state.
     */
    if (i2c_smbus_write_byte(client, 0) < 0) {
        dev_warn(&client->dev, "probe failed\n");
        goto exit_free;
    }

    data->type = id->driver_data;
    data->last_chan = 0;           /* force the first selection */

    /* Now create an adapter for each channel */
    for (num = 0; num < chips[data->type].nchans; num++) {
        force = 0;            /* dynamic adap number */
        class = 0;            /* no class by default */
        if (pdata) {
            if (num < pdata->num_modes) {
                /* force static number */
                force = pdata->modes[num].adap_id;
                class = pdata->modes[num].class;
            } else
                /* discard unconfigured channels */
                break;
        }

        data->virt_adaps[num] =
            i2c_add_mux_adapter(adap, &client->dev, client,
                force, num, class, pca954x_select_chan,
                (pdata && pdata->modes[num].deselect_on_exit)
                    ? pca954x_deselect_mux : NULL);

        if (data->virt_adaps[num] == NULL) {
            ret = -ENODEV;
            dev_err(&client->dev,
                "failed to register multiplexed adapter"
                " %d as bus %d\n", num, force);
            goto virt_reg_failed;
        }
    }

    dev_info(&client->dev,
         "registered %d multiplexed busses for I2C %s %s\n",
         num, chips[data->type].muxtype == pca954x_ismux
                ? "mux" : "switch", client->name);

    return 0;

virt_reg_failed:
    for (num--; num >= 0; num--)
        i2c_del_mux_adapter(data->virt_adaps[num]);
exit_free:
    kfree(data);
err:
    return ret;
}

static int pca954x_remove(struct i2c_client *client)
{
    struct pca954x *data = i2c_get_clientdata(client);
    const struct chip_desc *chip = &chips[data->type];
    int i, err;

    for (i = 0; i < chip->nchans; ++i)
        if (data->virt_adaps[i]) {
            err = i2c_del_mux_adapter(data->virt_adaps[i]);
            if (err)
                return err;
            data->virt_adaps[i] = NULL;
        }

    kfree(data);
    return 0;
}

static struct i2c_driver pca954x_driver = {
    .driver     = {
        .name   = "pca954x",
        .owner  = THIS_MODULE,
    },
    .probe      = pca954x_probe,
    .remove     = pca954x_remove,
    .id_table   = pca954x_id,
};

module_i2c_driver(pca954x_driver);

MODULE_AUTHOR("Rodolfo Giometti <[email protected]>");
MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
MODULE_LICENSE("GPL v2");