/*
 * I2C multiplexer
 *
 * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
 * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
 *
 * 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 <galak@kernel.crashing.org>
 * 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 <bkuschak@yahoo.com>
 * and
 *      pca9540.c from Jean Delvare <khali@linux-fr.org>.
 *
 * 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 <giometti@linux.it>");
MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
MODULE_LICENSE("GPL v2");