/*
 * I2C bridge driver for the Greybus "generic" I2C module.
 *
 * Copyright 2014 Google Inc.
 * Copyright 2014 Linaro Ltd.
 *
 * Released under the GPLv2 only.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/i2c.h>

#include "greybus.h"
#include "gbphy.h"

struct gb_i2c_device {
        struct gb_connection    *connection;
        struct gbphy_device     *gbphy_dev;

        u32                     functionality;

        struct i2c_adapter      adapter;
};

/*
 * Map Greybus i2c functionality bits into Linux ones
 */
static u32 gb_i2c_functionality_map(u32 gb_i2c_functionality)
{
        return gb_i2c_functionality;    /* All bits the same for now */
}

static int gb_i2c_functionality_operation(struct gb_i2c_device *gb_i2c_dev)
{
        struct gb_i2c_functionality_response response;
        u32 functionality;
        int ret;

        ret = gb_operation_sync(gb_i2c_dev->connection,
                                GB_I2C_TYPE_FUNCTIONALITY,
                                NULL, 0, &response, sizeof(response));
        if (ret)
                return ret;

        functionality = le32_to_cpu(response.functionality);
        gb_i2c_dev->functionality = gb_i2c_functionality_map(functionality);

        return 0;
}

/*
 * Map Linux i2c_msg flags into Greybus i2c transfer op flags.
 */
static u16 gb_i2c_transfer_op_flags_map(u16 flags)
{
        return flags;   /* All flags the same for now */
}

static void
gb_i2c_fill_transfer_op(struct gb_i2c_transfer_op *op, struct i2c_msg *msg)
{
        u16 flags = gb_i2c_transfer_op_flags_map(msg->flags);

        op->addr = cpu_to_le16(msg->addr);
        op->flags = cpu_to_le16(flags);
        op->size = cpu_to_le16(msg->len);
}

static struct gb_operation *
gb_i2c_operation_create(struct gb_connection *connection,
                        struct i2c_msg *msgs, u32 msg_count)
{
        struct gb_i2c_device *gb_i2c_dev = gb_connection_get_data(connection);
        struct gb_i2c_transfer_request *request;
        struct gb_operation *operation;
        struct gb_i2c_transfer_op *op;
        struct i2c_msg *msg;
        u32 data_out_size = 0;
        u32 data_in_size = 0;
        size_t request_size;
        void *data;
        u16 op_count;
        u32 i;

        if (msg_count > (u32)U16_MAX) {
                dev_err(&gb_i2c_dev->gbphy_dev->dev, "msg_count (%u) too big\n",
                        msg_count);
                return NULL;
        }
        op_count = (u16)msg_count;

        /*
         * In addition to space for all message descriptors we need
         * to have enough to hold all outbound message data.
         */
        msg = msgs;
        for (i = 0; i < msg_count; i++, msg++)
                if (msg->flags & I2C_M_RD)
                        data_in_size += (u32)msg->len;
                else
                        data_out_size += (u32)msg->len;

        request_size = sizeof(*request);
        request_size += msg_count * sizeof(*op);
        request_size += data_out_size;

        /* Response consists only of incoming data */
        operation = gb_operation_create(connection, GB_I2C_TYPE_TRANSFER,
                                request_size, data_in_size, GFP_KERNEL);
        if (!operation)
                return NULL;

        request = operation->request->payload;
        request->op_count = cpu_to_le16(op_count);
        /* Fill in the ops array */
        op = &request->ops[0];
        msg = msgs;
        for (i = 0; i < msg_count; i++)
                gb_i2c_fill_transfer_op(op++, msg++);

        if (!data_out_size)
                return operation;

        /* Copy over the outgoing data; it starts after the last op */
        data = op;
        msg = msgs;
        for (i = 0; i < msg_count; i++) {
                if (!(msg->flags & I2C_M_RD)) {
                        memcpy(data, msg->buf, msg->len);
                        data += msg->len;
                }
                msg++;
        }

        return operation;
}

static void gb_i2c_decode_response(struct i2c_msg *msgs, u32 msg_count,
                                struct gb_i2c_transfer_response *response)
{
        struct i2c_msg *msg = msgs;
        u8 *data;
        u32 i;

        if (!response)
                return;
        data = response->data;
        for (i = 0; i < msg_count; i++) {
                if (msg->flags & I2C_M_RD) {
                        memcpy(msg->buf, data, msg->len);
                        data += msg->len;
                }
                msg++;
        }
}

/*
 * Some i2c transfer operations return results that are expected.
 */
static bool gb_i2c_expected_transfer_error(int errno)
{
        return errno == -EAGAIN || errno == -ENODEV;
}

static int gb_i2c_transfer_operation(struct gb_i2c_device *gb_i2c_dev,
                                        struct i2c_msg *msgs, u32 msg_count)
{
        struct gb_connection *connection = gb_i2c_dev->connection;
        struct device *dev = &gb_i2c_dev->gbphy_dev->dev;
        struct gb_operation *operation;
        int ret;

        operation = gb_i2c_operation_create(connection, msgs, msg_count);
        if (!operation)
                return -ENOMEM;

        ret = gbphy_runtime_get_sync(gb_i2c_dev->gbphy_dev);
        if (ret)
                goto exit_operation_put;

        ret = gb_operation_request_send_sync(operation);
        if (!ret) {
                struct gb_i2c_transfer_response *response;

                response = operation->response->payload;
                gb_i2c_decode_response(msgs, msg_count, response);
                ret = msg_count;
        } else if (!gb_i2c_expected_transfer_error(ret)) {
                dev_err(dev, "transfer operation failed (%d)\n", ret);
        }

        gbphy_runtime_put_autosuspend(gb_i2c_dev->gbphy_dev);

exit_operation_put:
        gb_operation_put(operation);

        return ret;
}

static int gb_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                int msg_count)
{
        struct gb_i2c_device *gb_i2c_dev;

        gb_i2c_dev = i2c_get_adapdata(adap);

        return gb_i2c_transfer_operation(gb_i2c_dev, msgs, msg_count);
}

#if 0
/* Later */
static int gb_i2c_smbus_xfer(struct i2c_adapter *adap,
                        u16 addr, unsigned short flags, char read_write,
                        u8 command, int size, union i2c_smbus_data *data)
{
        struct gb_i2c_device *gb_i2c_dev;

        gb_i2c_dev = i2c_get_adapdata(adap);

        return 0;
}
#endif

static u32 gb_i2c_functionality(struct i2c_adapter *adap)
{
        struct gb_i2c_device *gb_i2c_dev = i2c_get_adapdata(adap);

        return gb_i2c_dev->functionality;
}

static const struct i2c_algorithm gb_i2c_algorithm = {
        .master_xfer    = gb_i2c_master_xfer,
        /* .smbus_xfer  = gb_i2c_smbus_xfer, */
        .functionality  = gb_i2c_functionality,
};

/*
 * Do initial setup of the i2c device.  This includes verifying we
 * can support it (based on the protocol version it advertises).
 * If that's OK, we get and cached its functionality bits.
 *
 * Note: gb_i2c_dev->connection is assumed to have been valid.
 */
static int gb_i2c_device_setup(struct gb_i2c_device *gb_i2c_dev)
{
        /* Assume the functionality never changes, just get it once */
        return gb_i2c_functionality_operation(gb_i2c_dev);
}

static int gb_i2c_probe(struct gbphy_device *gbphy_dev,
                         const struct gbphy_device_id *id)
{
        struct gb_connection *connection;
        struct gb_i2c_device *gb_i2c_dev;
        struct i2c_adapter *adapter;
        int ret;

        gb_i2c_dev = kzalloc(sizeof(*gb_i2c_dev), GFP_KERNEL);
        if (!gb_i2c_dev)
                return -ENOMEM;

        connection = gb_connection_create(gbphy_dev->bundle,
                                          le16_to_cpu(gbphy_dev->cport_desc->id),
                                          NULL);
        if (IS_ERR(connection)) {
                ret = PTR_ERR(connection);
                goto exit_i2cdev_free;
        }

        gb_i2c_dev->connection = connection;
        gb_connection_set_data(connection, gb_i2c_dev);
        gb_i2c_dev->gbphy_dev = gbphy_dev;
        gb_gbphy_set_data(gbphy_dev, gb_i2c_dev);

        ret = gb_connection_enable(connection);
        if (ret)
                goto exit_connection_destroy;

        ret = gb_i2c_device_setup(gb_i2c_dev);
        if (ret)
                goto exit_connection_disable;

        /* Looks good; up our i2c adapter */
        adapter = &gb_i2c_dev->adapter;
        adapter->owner = THIS_MODULE;
        adapter->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
        adapter->algo = &gb_i2c_algorithm;
        /* adapter->algo_data = what? */

        adapter->dev.parent = &gbphy_dev->dev;
        snprintf(adapter->name, sizeof(adapter->name), "Greybus i2c adapter");
        i2c_set_adapdata(adapter, gb_i2c_dev);

        ret = i2c_add_adapter(adapter);
        if (ret)
                goto exit_connection_disable;

        gbphy_runtime_put_autosuspend(gbphy_dev);
        return 0;

exit_connection_disable:
        gb_connection_disable(connection);
exit_connection_destroy:
        gb_connection_destroy(connection);
exit_i2cdev_free:
        kfree(gb_i2c_dev);

        return ret;
}

static void gb_i2c_remove(struct gbphy_device *gbphy_dev)
{
        struct gb_i2c_device *gb_i2c_dev = gb_gbphy_get_data(gbphy_dev);
        struct gb_connection *connection = gb_i2c_dev->connection;
        int ret;

        ret = gbphy_runtime_get_sync(gbphy_dev);
        if (ret)
                gbphy_runtime_get_noresume(gbphy_dev);

        i2c_del_adapter(&gb_i2c_dev->adapter);
        gb_connection_disable(connection);
        gb_connection_destroy(connection);
        kfree(gb_i2c_dev);
}

static const struct gbphy_device_id gb_i2c_id_table[] = {
        { GBPHY_PROTOCOL(GREYBUS_PROTOCOL_I2C) },
        { },
};
MODULE_DEVICE_TABLE(gbphy, gb_i2c_id_table);

static struct gbphy_driver i2c_driver = {
        .name           = "i2c",
        .probe          = gb_i2c_probe,
        .remove         = gb_i2c_remove,
        .id_table       = gb_i2c_id_table,
};

module_gbphy_driver(i2c_driver);
MODULE_LICENSE("GPL v2");