// SPDX-License-Identifier: GPL-2.0+
//
// em28xx-i2c.c - driver for Empia EM2800/EM2820/2840 USB video capture devices
//
// Copyright (C) 2005 Ludovico Cavedon <cavedon@sssup.it>
//                    Markus Rechberger <mrechberger@gmail.com>
//                    Mauro Carvalho Chehab <mchehab@kernel.org>
//                    Sascha Sommer <saschasommer@freenet.de>
// Copyright (C) 2013 Frank Schäfer <fschaefer.oss@googlemail.com>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

#include "em28xx.h"

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/usb.h>
#include <linux/i2c.h>
#include <linux/jiffies.h>

#include "tuner-xc2028.h"
#include <media/v4l2-common.h>
#include <media/tuner.h>

/* ----------------------------------------------------------- */

static unsigned int i2c_scan;
module_param(i2c_scan, int, 0444);
MODULE_PARM_DESC(i2c_scan, "scan i2c bus at insmod time");

static unsigned int i2c_debug;
module_param(i2c_debug, int, 0644);
MODULE_PARM_DESC(i2c_debug, "i2c debug message level (1: normal debug, 2: show I2C transfers)");

#define dprintk(level, fmt, arg...) do {                                \
        if (i2c_debug > level)                                          \
                dev_printk(KERN_DEBUG, &dev->intf->dev,                 \
                           "i2c: %s: " fmt, __func__, ## arg);          \
} while (0)

/*
 * Time in msecs to wait for i2c xfers to finish.
 * 35ms is the maximum time a SMBUS device could wait when
 * clock stretching is used. As the transfer itself will take
 * some time to happen, set it to 35 ms.
 *
 * Ok, I2C doesn't specify any limit. So, eventually, we may need
 * to increase this timeout.
 */
#define EM28XX_I2C_XFER_TIMEOUT         35 /* ms */

static int em28xx_i2c_timeout(struct em28xx *dev)
{
        int time = EM28XX_I2C_XFER_TIMEOUT;

        switch (dev->i2c_speed & 0x03) {
        case EM28XX_I2C_FREQ_25_KHZ:
                time += 4;              /* Assume 4 ms for transfers */
                break;
        case EM28XX_I2C_FREQ_100_KHZ:
        case EM28XX_I2C_FREQ_400_KHZ:
                time += 1;              /* Assume 1 ms for transfers */
                break;
        default: /* EM28XX_I2C_FREQ_1_5_MHZ */
                break;
        }

        return msecs_to_jiffies(time);
}

/*
 * em2800_i2c_send_bytes()
 * send up to 4 bytes to the em2800 i2c device
 */
static int em2800_i2c_send_bytes(struct em28xx *dev, u8 addr, u8 *buf, u16 len)
{
        unsigned long timeout = jiffies + em28xx_i2c_timeout(dev);
        int ret;
        u8 b2[6];

        if (len < 1 || len > 4)
                return -EOPNOTSUPP;

        b2[5] = 0x80 + len - 1;
        b2[4] = addr;
        b2[3] = buf[0];
        if (len > 1)
                b2[2] = buf[1];
        if (len > 2)
                b2[1] = buf[2];
        if (len > 3)
                b2[0] = buf[3];

        /* trigger write */
        ret = dev->em28xx_write_regs(dev, 4 - len, &b2[4 - len], 2 + len);
        if (ret != 2 + len) {
                dev_warn(&dev->intf->dev,
                         "failed to trigger write to i2c address 0x%x (error=%i)\n",
                            addr, ret);
                return (ret < 0) ? ret : -EIO;
        }
        /* wait for completion */
        while (time_is_after_jiffies(timeout)) {
                ret = dev->em28xx_read_reg(dev, 0x05);
                if (ret == 0x80 + len - 1)
                        return len;
                if (ret == 0x94 + len - 1) {
                        dprintk(1, "R05 returned 0x%02x: I2C ACK error\n", ret);
                        return -ENXIO;
                }
                if (ret < 0) {
                        dev_warn(&dev->intf->dev,
                                 "failed to get i2c transfer status from bridge register (error=%i)\n",
                                ret);
                        return ret;
                }
                usleep_range(5000, 6000);
        }
        dprintk(0, "write to i2c device at 0x%x timed out\n", addr);
        return -ETIMEDOUT;
}

/*
 * em2800_i2c_recv_bytes()
 * read up to 4 bytes from the em2800 i2c device
 */
static int em2800_i2c_recv_bytes(struct em28xx *dev, u8 addr, u8 *buf, u16 len)
{
        unsigned long timeout = jiffies + em28xx_i2c_timeout(dev);
        u8 buf2[4];
        int ret;
        int i;

        if (len < 1 || len > 4)
                return -EOPNOTSUPP;

        /* trigger read */
        buf2[1] = 0x84 + len - 1;
        buf2[0] = addr;
        ret = dev->em28xx_write_regs(dev, 0x04, buf2, 2);
        if (ret != 2) {
                dev_warn(&dev->intf->dev,
                         "failed to trigger read from i2c address 0x%x (error=%i)\n",
                         addr, ret);
                return (ret < 0) ? ret : -EIO;
        }

        /* wait for completion */
        while (time_is_after_jiffies(timeout)) {
                ret = dev->em28xx_read_reg(dev, 0x05);
                if (ret == 0x84 + len - 1)
                        break;
                if (ret == 0x94 + len - 1) {
                        dprintk(1, "R05 returned 0x%02x: I2C ACK error\n",
                                ret);
                        return -ENXIO;
                }
                if (ret < 0) {
                        dev_warn(&dev->intf->dev,
                                 "failed to get i2c transfer status from bridge register (error=%i)\n",
                                 ret);
                        return ret;
                }
                usleep_range(5000, 6000);
        }
        if (ret != 0x84 + len - 1)
                dprintk(0, "read from i2c device at 0x%x timed out\n", addr);

        /* get the received message */
        ret = dev->em28xx_read_reg_req_len(dev, 0x00, 4 - len, buf2, len);
        if (ret != len) {
                dev_warn(&dev->intf->dev,
                         "reading from i2c device at 0x%x failed: couldn't get the received message from the bridge (error=%i)\n",
                         addr, ret);
                return (ret < 0) ? ret : -EIO;
        }
        for (i = 0; i < len; i++)
                buf[i] = buf2[len - 1 - i];

        return ret;
}

/*
 * em2800_i2c_check_for_device()
 * check if there is an i2c device at the supplied address
 */
static int em2800_i2c_check_for_device(struct em28xx *dev, u8 addr)
{
        u8 buf;
        int ret;

        ret = em2800_i2c_recv_bytes(dev, addr, &buf, 1);
        if (ret == 1)
                return 0;
        return (ret < 0) ? ret : -EIO;
}

/*
 * em28xx_i2c_send_bytes()
 */
static int em28xx_i2c_send_bytes(struct em28xx *dev, u16 addr, u8 *buf,
                                 u16 len, int stop)
{
        unsigned long timeout = jiffies + em28xx_i2c_timeout(dev);
        int ret;

        if (len < 1 || len > 64)
                return -EOPNOTSUPP;
        /*
         * NOTE: limited by the USB ctrl message constraints
         * Zero length reads always succeed, even if no device is connected
         */

        /* Write to i2c device */
        ret = dev->em28xx_write_regs_req(dev, stop ? 2 : 3, addr, buf, len);
        if (ret != len) {
                if (ret < 0) {
                        dev_warn(&dev->intf->dev,
                                 "writing to i2c device at 0x%x failed (error=%i)\n",
                                 addr, ret);
                        return ret;
                }
                dev_warn(&dev->intf->dev,
                         "%i bytes write to i2c device at 0x%x requested, but %i bytes written\n",
                                len, addr, ret);
                return -EIO;
        }

        /* wait for completion */
        while (time_is_after_jiffies(timeout)) {
                ret = dev->em28xx_read_reg(dev, 0x05);
                if (ret == 0) /* success */
                        return len;
                if (ret == 0x10) {
                        dprintk(1, "I2C ACK error on writing to addr 0x%02x\n",
                                addr);
                        return -ENXIO;
                }
                if (ret < 0) {
                        dev_warn(&dev->intf->dev,
                                 "failed to get i2c transfer status from bridge register (error=%i)\n",
                                 ret);
                        return ret;
                }
                usleep_range(5000, 6000);
                /*
                 * NOTE: do we really have to wait for success ?
                 * Never seen anything else than 0x00 or 0x10
                 * (even with high payload) ...
                 */
        }

        if (ret == 0x02 || ret == 0x04) {
                /* NOTE: these errors seem to be related to clock stretching */
                dprintk(0,
                        "write to i2c device at 0x%x timed out (status=%i)\n",
                        addr, ret);
                return -ETIMEDOUT;
        }

        dev_warn(&dev->intf->dev,
                 "write to i2c device at 0x%x failed with unknown error (status=%i)\n",
                 addr, ret);
        return -EIO;
}

/*
 * em28xx_i2c_recv_bytes()
 * read a byte from the i2c device
 */
static int em28xx_i2c_recv_bytes(struct em28xx *dev, u16 addr, u8 *buf, u16 len)
{
        int ret;

        if (len < 1 || len > 64)
                return -EOPNOTSUPP;
        /*
         * NOTE: limited by the USB ctrl message constraints
         * Zero length reads always succeed, even if no device is connected
         */

        /* Read data from i2c device */
        ret = dev->em28xx_read_reg_req_len(dev, 2, addr, buf, len);
        if (ret < 0) {
                dev_warn(&dev->intf->dev,
                         "reading from i2c device at 0x%x failed (error=%i)\n",
                         addr, ret);
                return ret;
        }
        /*
         * NOTE: some devices with two i2c buses have the bad habit to return 0
         * bytes if we are on bus B AND there was no write attempt to the
         * specified slave address before AND no device is present at the
         * requested slave address.
         * Anyway, the next check will fail with -ENXIO in this case, so avoid
         * spamming the system log on device probing and do nothing here.
         */

        /* Check success of the i2c operation */
        ret = dev->em28xx_read_reg(dev, 0x05);
        if (ret == 0) /* success */
                return len;
        if (ret < 0) {
                dev_warn(&dev->intf->dev,
                         "failed to get i2c transfer status from bridge register (error=%i)\n",
                         ret);
                return ret;
        }
        if (ret == 0x10) {
                dprintk(1, "I2C ACK error on writing to addr 0x%02x\n",
                        addr);
                return -ENXIO;
        }

        if (ret == 0x02 || ret == 0x04) {
                /* NOTE: these errors seem to be related to clock stretching */
                dprintk(0,
                        "write to i2c device at 0x%x timed out (status=%i)\n",
                        addr, ret);
                return -ETIMEDOUT;
        }

        dev_warn(&dev->intf->dev,
                 "write to i2c device at 0x%x failed with unknown error (status=%i)\n",
                 addr, ret);
        return -EIO;
}

/*
 * em28xx_i2c_check_for_device()
 * check if there is a i2c_device at the supplied address
 */
static int em28xx_i2c_check_for_device(struct em28xx *dev, u16 addr)
{
        int ret;
        u8 buf;

        ret = em28xx_i2c_recv_bytes(dev, addr, &buf, 1);
        if (ret == 1)
                return 0;
        return (ret < 0) ? ret : -EIO;
}

/*
 * em25xx_bus_B_send_bytes
 * write bytes to the i2c device
 */
static int em25xx_bus_B_send_bytes(struct em28xx *dev, u16 addr, u8 *buf,
                                   u16 len)
{
        int ret;

        if (len < 1 || len > 64)
                return -EOPNOTSUPP;
        /*
         * NOTE: limited by the USB ctrl message constraints
         * Zero length reads always succeed, even if no device is connected
         */

        /* Set register and write value */
        ret = dev->em28xx_write_regs_req(dev, 0x06, addr, buf, len);
        if (ret != len) {
                if (ret < 0) {
                        dev_warn(&dev->intf->dev,
                                 "writing to i2c device at 0x%x failed (error=%i)\n",
                                 addr, ret);
                        return ret;
                }

                dev_warn(&dev->intf->dev,
                         "%i bytes write to i2c device at 0x%x requested, but %i bytes written\n",
                         len, addr, ret);
                return -EIO;
        }
        /* Check success */
        ret = dev->em28xx_read_reg_req(dev, 0x08, 0x0000);
        /*
         * NOTE: the only error we've seen so far is
         * 0x01 when the slave device is not present
         */
        if (!ret)
                return len;

        if (ret > 0) {
                dprintk(1, "Bus B R08 returned 0x%02x: I2C ACK error\n", ret);
                return -ENXIO;
        }

        return ret;
        /*
         * NOTE: With chip types (other chip IDs) which actually don't support
         * this operation, it seems to succeed ALWAYS ! (even if there is no
         * slave device or even no second i2c bus provided)
         */
}

/*
 * em25xx_bus_B_recv_bytes
 * read bytes from the i2c device
 */
static int em25xx_bus_B_recv_bytes(struct em28xx *dev, u16 addr, u8 *buf,
                                   u16 len)
{
        int ret;

        if (len < 1 || len > 64)
                return -EOPNOTSUPP;
        /*
         * NOTE: limited by the USB ctrl message constraints
         * Zero length reads always succeed, even if no device is connected
         */

        /* Read value */
        ret = dev->em28xx_read_reg_req_len(dev, 0x06, addr, buf, len);
        if (ret < 0) {
                dev_warn(&dev->intf->dev,
                         "reading from i2c device at 0x%x failed (error=%i)\n",
                         addr, ret);
                return ret;
        }
        /*
         * NOTE: some devices with two i2c buses have the bad habit to return 0
         * bytes if we are on bus B AND there was no write attempt to the
         * specified slave address before AND no device is present at the
         * requested slave address.
         * Anyway, the next check will fail with -ENXIO in this case, so avoid
         * spamming the system log on device probing and do nothing here.
         */

        /* Check success */
        ret = dev->em28xx_read_reg_req(dev, 0x08, 0x0000);
        /*
         * NOTE: the only error we've seen so far is
         * 0x01 when the slave device is not present
         */
        if (!ret)
                return len;

        if (ret > 0) {
                dprintk(1, "Bus B R08 returned 0x%02x: I2C ACK error\n", ret);
                return -ENXIO;
        }

        return ret;
        /*
         * NOTE: With chip types (other chip IDs) which actually don't support
         * this operation, it seems to succeed ALWAYS ! (even if there is no
         * slave device or even no second i2c bus provided)
         */
}

/*
 * em25xx_bus_B_check_for_device()
 * check if there is a i2c device at the supplied address
 */
static int em25xx_bus_B_check_for_device(struct em28xx *dev, u16 addr)
{
        u8 buf;
        int ret;

        ret = em25xx_bus_B_recv_bytes(dev, addr, &buf, 1);
        if (ret < 0)
                return ret;

        return 0;
        /*
         * NOTE: With chips which do not support this operation,
         * it seems to succeed ALWAYS ! (even if no device connected)
         */
}

static inline int i2c_check_for_device(struct em28xx_i2c_bus *i2c_bus, u16 addr)
{
        struct em28xx *dev = i2c_bus->dev;
        int rc = -EOPNOTSUPP;

        if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM28XX)
                rc = em28xx_i2c_check_for_device(dev, addr);
        else if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM2800)
                rc = em2800_i2c_check_for_device(dev, addr);
        else if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM25XX_BUS_B)
                rc = em25xx_bus_B_check_for_device(dev, addr);
        return rc;
}

static inline int i2c_recv_bytes(struct em28xx_i2c_bus *i2c_bus,
                                 struct i2c_msg msg)
{
        struct em28xx *dev = i2c_bus->dev;
        u16 addr = msg.addr << 1;
        int rc = -EOPNOTSUPP;

        if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM28XX)
                rc = em28xx_i2c_recv_bytes(dev, addr, msg.buf, msg.len);
        else if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM2800)
                rc = em2800_i2c_recv_bytes(dev, addr, msg.buf, msg.len);
        else if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM25XX_BUS_B)
                rc = em25xx_bus_B_recv_bytes(dev, addr, msg.buf, msg.len);
        return rc;
}

static inline int i2c_send_bytes(struct em28xx_i2c_bus *i2c_bus,
                                 struct i2c_msg msg, int stop)
{
        struct em28xx *dev = i2c_bus->dev;
        u16 addr = msg.addr << 1;
        int rc = -EOPNOTSUPP;

        if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM28XX)
                rc = em28xx_i2c_send_bytes(dev, addr, msg.buf, msg.len, stop);
        else if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM2800)
                rc = em2800_i2c_send_bytes(dev, addr, msg.buf, msg.len);
        else if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM25XX_BUS_B)
                rc = em25xx_bus_B_send_bytes(dev, addr, msg.buf, msg.len);
        return rc;
}

/*
 * em28xx_i2c_xfer()
 * the main i2c transfer function
 */
static int em28xx_i2c_xfer(struct i2c_adapter *i2c_adap,
                           struct i2c_msg msgs[], int num)
{
        struct em28xx_i2c_bus *i2c_bus = i2c_adap->algo_data;
        struct em28xx *dev = i2c_bus->dev;
        unsigned int bus = i2c_bus->bus;
        int addr, rc, i;
        u8 reg;

        /*
         * prevent i2c xfer attempts after device is disconnected
         * some fe's try to do i2c writes/reads from their release
         * interfaces when called in disconnect path
         */
        if (dev->disconnected)
                return -ENODEV;

        if (!rt_mutex_trylock(&dev->i2c_bus_lock))
                return -EAGAIN;

        /* Switch I2C bus if needed */
        if (bus != dev->cur_i2c_bus &&
            i2c_bus->algo_type == EM28XX_I2C_ALGO_EM28XX) {
                if (bus == 1)
                        reg = EM2874_I2C_SECONDARY_BUS_SELECT;
                else
                        reg = 0;
                em28xx_write_reg_bits(dev, EM28XX_R06_I2C_CLK, reg,
                                      EM2874_I2C_SECONDARY_BUS_SELECT);
                dev->cur_i2c_bus = bus;
        }

        for (i = 0; i < num; i++) {
                addr = msgs[i].addr << 1;
                if (!msgs[i].len) {
                        /*
                         * no len: check only for device presence
                         * This code is only called during device probe.
                         */
                        rc = i2c_check_for_device(i2c_bus, addr);

                        if (rc == -ENXIO)
                                rc = -ENODEV;
                } else if (msgs[i].flags & I2C_M_RD) {
                        /* read bytes */
                        rc = i2c_recv_bytes(i2c_bus, msgs[i]);
                } else {
                        /* write bytes */
                        rc = i2c_send_bytes(i2c_bus, msgs[i], i == num - 1);
                }

                if (rc < 0)
                        goto error;

                dprintk(2, "%s %s addr=%02x len=%d: %*ph\n",
                        (msgs[i].flags & I2C_M_RD) ? "read" : "write",
                        i == num - 1 ? "stop" : "nonstop",
                        addr, msgs[i].len,
                        msgs[i].len, msgs[i].buf);
        }

        rt_mutex_unlock(&dev->i2c_bus_lock);
        return num;

error:
        dprintk(2, "%s %s addr=%02x len=%d: %sERROR: %i\n",
                (msgs[i].flags & I2C_M_RD) ? "read" : "write",
                i == num - 1 ? "stop" : "nonstop",
                addr, msgs[i].len,
                (rc == -ENODEV) ? "no device " : "",
                rc);

        rt_mutex_unlock(&dev->i2c_bus_lock);
        return rc;
}

/*
 * based on linux/sunrpc/svcauth.h and linux/hash.h
 * The original hash function returns a different value, if arch is x86_64
 * or i386.
 */
static inline unsigned long em28xx_hash_mem(char *buf, int length, int bits)
{
        unsigned long hash = 0;
        unsigned long l = 0;
        int len = 0;
        unsigned char c;

        do {
                if (len == length) {
                        c = (char)len;
                        len = -1;
                } else {
                        c = *buf++;
                }
                l = (l << 8) | c;
                len++;
                if ((len & (32 / 8 - 1)) == 0)
                        hash = ((hash ^ l) * 0x9e370001UL);
        } while (len);

        return (hash >> (32 - bits)) & 0xffffffffUL;
}

/*
 * Helper function to read data blocks from i2c clients with 8 or 16 bit
 * address width, 8 bit register width and auto incrementation been activated
 */
static int em28xx_i2c_read_block(struct em28xx *dev, unsigned int bus, u16 addr,
                                 bool addr_w16, u16 len, u8 *data)
{
        int remain = len, rsize, rsize_max, ret;
        u8 buf[2];

        /* Sanity check */
        if (addr + remain > (addr_w16 * 0xff00 + 0xff + 1))
                return -EINVAL;
        /* Select address */
        buf[0] = addr >> 8;
        buf[1] = addr & 0xff;
        ret = i2c_master_send(&dev->i2c_client[bus],
                              buf + !addr_w16, 1 + addr_w16);
        if (ret < 0)
                return ret;
        /* Read data */
        if (dev->board.is_em2800)
                rsize_max = 4;
        else
                rsize_max = 64;
        while (remain > 0) {
                if (remain > rsize_max)
                        rsize = rsize_max;
                else
                        rsize = remain;

                ret = i2c_master_recv(&dev->i2c_client[bus], data, rsize);
                if (ret < 0)
                        return ret;

                remain -= rsize;
                data += rsize;
        }

        return len;
}

static int em28xx_i2c_eeprom(struct em28xx *dev, unsigned int bus,
                             u8 **eedata, u16 *eedata_len)
{
        const u16 len = 256;
        /*
         * FIXME common length/size for bytes to read, to display, hash
         * calculation and returned device dataset. Simplifies the code a lot,
         * but we might have to deal with multiple sizes in the future !
         */
        int err;
        struct em28xx_eeprom *dev_config;
        u8 buf, *data;

        *eedata = NULL;
        *eedata_len = 0;

        /* EEPROM is always on i2c bus 0 on all known devices. */

        dev->i2c_client[bus].addr = 0xa0 >> 1;

        /* Check if board has eeprom */
        err = i2c_master_recv(&dev->i2c_client[bus], &buf, 0);
        if (err < 0) {
                dev_info(&dev->intf->dev, "board has no eeprom\n");
                return -ENODEV;
        }

        data = kzalloc(len, GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        /* Read EEPROM content */
        err = em28xx_i2c_read_block(dev, bus, 0x0000,
                                    dev->eeprom_addrwidth_16bit,
                                    len, data);
        if (err != len) {
                dev_err(&dev->intf->dev,
                        "failed to read eeprom (err=%d)\n", err);
                goto error;
        }

        if (i2c_debug) {
                /* Display eeprom content */
                print_hex_dump(KERN_DEBUG, "em28xx eeprom ", DUMP_PREFIX_OFFSET,
                               16, 1, data, len, true);

                if (dev->eeprom_addrwidth_16bit)
                        dev_info(&dev->intf->dev,
                                 "eeprom %06x: ... (skipped)\n", 256);
        }

        if (dev->eeprom_addrwidth_16bit &&
            data[0] == 0x26 && data[3] == 0x00) {
                /* new eeprom format; size 4-64kb */
                u16 mc_start;
                u16 hwconf_offset;

                dev->hash = em28xx_hash_mem(data, len, 32);
                mc_start = (data[1] << 8) + 4;  /* usually 0x0004 */

                dev_info(&dev->intf->dev,
                         "EEPROM ID = %4ph, EEPROM hash = 0x%08lx\n",
                         data, dev->hash);
                dev_info(&dev->intf->dev,
                         "EEPROM info:\n");
                dev_info(&dev->intf->dev,
                         "\tmicrocode start address = 0x%04x, boot configuration = 0x%02x\n",
                         mc_start, data[2]);
                /*
                 * boot configuration (address 0x0002):
                 * [0]   microcode download speed: 1 = 400 kHz; 0 = 100 kHz
                 * [1]   always selects 12 kb RAM
                 * [2]   USB device speed: 1 = force Full Speed; 0 = auto detect
                 * [4]   1 = force fast mode and no suspend for device testing
                 * [5:7] USB PHY tuning registers; determined by device
                 *       characterization
                 */

                /*
                 * Read hardware config dataset offset from address
                 * (microcode start + 46)
                 */
                err = em28xx_i2c_read_block(dev, bus, mc_start + 46, 1, 2,
                                            data);
                if (err != 2) {
                        dev_err(&dev->intf->dev,
                                "failed to read hardware configuration data from eeprom (err=%d)\n",
                                err);
                        goto error;
                }

                /* Calculate hardware config dataset start address */
                hwconf_offset = mc_start + data[0] + (data[1] << 8);

                /* Read hardware config dataset */
                /*
                 * NOTE: the microcode copy can be multiple pages long, but
                 * we assume the hardware config dataset is the same as in
                 * the old eeprom and not longer than 256 bytes.
                 * tveeprom is currently also limited to 256 bytes.
                 */
                err = em28xx_i2c_read_block(dev, bus, hwconf_offset, 1, len,
                                            data);
                if (err != len) {
                        dev_err(&dev->intf->dev,
                                "failed to read hardware configuration data from eeprom (err=%d)\n",
                                err);
                        goto error;
                }

                /* Verify hardware config dataset */
                /* NOTE: not all devices provide this type of dataset */
                if (data[0] != 0x1a || data[1] != 0xeb ||
                    data[2] != 0x67 || data[3] != 0x95) {
                        dev_info(&dev->intf->dev,
                                 "\tno hardware configuration dataset found in eeprom\n");
                        kfree(data);
                        return 0;
                }

                /*
                 * TODO: decrypt eeprom data for camera bridges
                 * (em25xx, em276x+)
                 */

        } else if (!dev->eeprom_addrwidth_16bit &&
                   data[0] == 0x1a && data[1] == 0xeb &&
                   data[2] == 0x67 && data[3] == 0x95) {
                dev->hash = em28xx_hash_mem(data, len, 32);
                dev_info(&dev->intf->dev,
                         "EEPROM ID = %4ph, EEPROM hash = 0x%08lx\n",
                         data, dev->hash);
                dev_info(&dev->intf->dev,
                         "EEPROM info:\n");
        } else {
                dev_info(&dev->intf->dev,
                         "unknown eeprom format or eeprom corrupted !\n");
                err = -ENODEV;
                goto error;
        }

        *eedata = data;
        *eedata_len = len;
        dev_config = (void *)*eedata;

        switch (le16_to_cpu(dev_config->chip_conf) >> 4 & 0x3) {
        case 0:
                dev_info(&dev->intf->dev, "\tNo audio on board.\n");
                break;
        case 1:
                dev_info(&dev->intf->dev, "\tAC97 audio (5 sample rates)\n");
                break;
        case 2:
                if (dev->chip_id < CHIP_ID_EM2860)
                        dev_info(&dev->intf->dev,
                                 "\tI2S audio, sample rate=32k\n");
                else
                        dev_info(&dev->intf->dev,
                                 "\tI2S audio, 3 sample rates\n");
                break;
        case 3:
                if (dev->chip_id < CHIP_ID_EM2860)
                        dev_info(&dev->intf->dev,
                                 "\tI2S audio, 3 sample rates\n");
                else
                        dev_info(&dev->intf->dev,
                                 "\tI2S audio, 5 sample rates\n");
                break;
        }

        if (le16_to_cpu(dev_config->chip_conf) & 1 << 3)
                dev_info(&dev->intf->dev, "\tUSB Remote wakeup capable\n");

        if (le16_to_cpu(dev_config->chip_conf) & 1 << 2)
                dev_info(&dev->intf->dev, "\tUSB Self power capable\n");

        switch (le16_to_cpu(dev_config->chip_conf) & 0x3) {
        case 0:
                dev_info(&dev->intf->dev, "\t500mA max power\n");
                break;
        case 1:
                dev_info(&dev->intf->dev, "\t400mA max power\n");
                break;
        case 2:
                dev_info(&dev->intf->dev, "\t300mA max power\n");
                break;
        case 3:
                dev_info(&dev->intf->dev, "\t200mA max power\n");
                break;
        }
        dev_info(&dev->intf->dev,
                 "\tTable at offset 0x%02x, strings=0x%04x, 0x%04x, 0x%04x\n",
                 dev_config->string_idx_table,
                 le16_to_cpu(dev_config->string1),
                 le16_to_cpu(dev_config->string2),
                 le16_to_cpu(dev_config->string3));

        return 0;

error:
        kfree(data);
        return err;
}

/* ----------------------------------------------------------- */

/*
 * functionality()
 */
static u32 functionality(struct i2c_adapter *i2c_adap)
{
        struct em28xx_i2c_bus *i2c_bus = i2c_adap->algo_data;

        if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM28XX ||
            i2c_bus->algo_type == EM28XX_I2C_ALGO_EM25XX_BUS_B) {
                return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
        } else if (i2c_bus->algo_type == EM28XX_I2C_ALGO_EM2800)  {
                return (I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL) &
                        ~I2C_FUNC_SMBUS_WRITE_BLOCK_DATA;
        }

        WARN(1, "Unknown i2c bus algorithm.\n");
        return 0;
}

static const struct i2c_algorithm em28xx_algo = {
        .master_xfer   = em28xx_i2c_xfer,
        .functionality = functionality,
};

static const struct i2c_adapter em28xx_adap_template = {
        .owner = THIS_MODULE,
        .name = "em28xx",
        .algo = &em28xx_algo,
};

static const struct i2c_client em28xx_client_template = {
        .name = "em28xx internal",
};

/* ----------------------------------------------------------- */

/*
 * i2c_devs
 * incomplete list of known devices
 */
static char *i2c_devs[128] = {
        [0x1c >> 1] = "lgdt330x",
        [0x3e >> 1] = "remote IR sensor",
        [0x4a >> 1] = "saa7113h",
        [0x52 >> 1] = "drxk",
        [0x60 >> 1] = "remote IR sensor",
        [0x8e >> 1] = "remote IR sensor",
        [0x86 >> 1] = "tda9887",
        [0x80 >> 1] = "msp34xx",
        [0x88 >> 1] = "msp34xx",
        [0xa0 >> 1] = "eeprom",
        [0xb0 >> 1] = "tda9874",
        [0xb8 >> 1] = "tvp5150a",
        [0xba >> 1] = "webcam sensor or tvp5150a",
        [0xc0 >> 1] = "tuner (analog)",
        [0xc2 >> 1] = "tuner (analog)",
        [0xc4 >> 1] = "tuner (analog)",
        [0xc6 >> 1] = "tuner (analog)",
};

/*
 * do_i2c_scan()
 * check i2c address range for devices
 */
void em28xx_do_i2c_scan(struct em28xx *dev, unsigned int bus)
{
        u8 i2c_devicelist[128];
        unsigned char buf;
        int i, rc;

        memset(i2c_devicelist, 0, sizeof(i2c_devicelist));

        for (i = 0; i < ARRAY_SIZE(i2c_devs); i++) {
                dev->i2c_client[bus].addr = i;
                rc = i2c_master_recv(&dev->i2c_client[bus], &buf, 0);
                if (rc < 0)
                        continue;
                i2c_devicelist[i] = i;
                dev_info(&dev->intf->dev,
                         "found i2c device @ 0x%x on bus %d [%s]\n",
                         i << 1, bus, i2c_devs[i] ? i2c_devs[i] : "???");
        }

        if (bus == dev->def_i2c_bus)
                dev->i2c_hash = em28xx_hash_mem(i2c_devicelist,
                                                sizeof(i2c_devicelist), 32);
}

/*
 * em28xx_i2c_register()
 * register i2c bus
 */
int em28xx_i2c_register(struct em28xx *dev, unsigned int bus,
                        enum em28xx_i2c_algo_type algo_type)
{
        int retval;

        if (WARN_ON(!dev->em28xx_write_regs || !dev->em28xx_read_reg ||
                    !dev->em28xx_write_regs_req || !dev->em28xx_read_reg_req))
                return -ENODEV;

        if (bus >= NUM_I2C_BUSES)
                return -ENODEV;

        dev->i2c_adap[bus] = em28xx_adap_template;
        dev->i2c_adap[bus].dev.parent = &dev->intf->dev;
        strscpy(dev->i2c_adap[bus].name, dev_name(&dev->intf->dev),
                sizeof(dev->i2c_adap[bus].name));

        dev->i2c_bus[bus].bus = bus;
        dev->i2c_bus[bus].algo_type = algo_type;
        dev->i2c_bus[bus].dev = dev;
        dev->i2c_adap[bus].algo_data = &dev->i2c_bus[bus];

        retval = i2c_add_adapter(&dev->i2c_adap[bus]);
        if (retval < 0) {
                dev_err(&dev->intf->dev,
                        "%s: i2c_add_adapter failed! retval [%d]\n",
                        __func__, retval);

                return retval;
        }

        dev->i2c_client[bus] = em28xx_client_template;
        dev->i2c_client[bus].adapter = &dev->i2c_adap[bus];

        /* Up to now, all eeproms are at bus 0 */
        if (!bus) {
                retval = em28xx_i2c_eeprom(dev, bus,
                                           &dev->eedata, &dev->eedata_len);
                if (retval < 0 && retval != -ENODEV) {
                        dev_err(&dev->intf->dev,
                                "%s: em28xx_i2_eeprom failed! retval [%d]\n",
                                __func__, retval);
                }
        }

        if (i2c_scan)
                em28xx_do_i2c_scan(dev, bus);

        return 0;
}

/*
 * em28xx_i2c_unregister()
 * unregister i2c_bus
 */
int em28xx_i2c_unregister(struct em28xx *dev, unsigned int bus)
{
        if (bus >= NUM_I2C_BUSES)
                return -ENODEV;

        i2c_del_adapter(&dev->i2c_adap[bus]);
        return 0;
}