dev->board.i2c_speed = EM28XX_I2C_CLK_WAIT_ENABLE |
                                       EM28XX_I2C_FREQ_100_KHZ;
 
-       if (dev->board.def_i2c_bus == 1)
-               dev->board.i2c_speed |= EM2874_I2C_SECONDARY_BUS_SELECT;
+       /* Should be initialized early, for I2C to work */
+       dev->def_i2c_bus = dev->board.def_i2c_bus;
 }
 
 
 
        /* user did not request i2c scanning => do it now */
        if (!dev->i2c_hash)
-               em28xx_do_i2c_scan(dev);
+               em28xx_do_i2c_scan(dev, dev->def_i2c_bus);
 
        for (i = 0; i < ARRAY_SIZE(em28xx_i2c_hash); i++) {
                if (dev->i2c_hash == em28xx_i2c_hash[i].hash) {
 
        em28xx_release_analog_resources(dev);
 
-       em28xx_i2c_unregister(dev);
+       if (dev->def_i2c_bus)
+               em28xx_i2c_unregister(dev, 1);
+       em28xx_i2c_unregister(dev, 0);
 
        v4l2_ctrl_handler_free(&dev->ctrl_handler);
 
        v4l2_ctrl_handler_init(hdl, 8);
        dev->v4l2_dev.ctrl_handler = hdl;
 
-       /* register i2c bus */
-       retval = em28xx_i2c_register(dev);
+       rt_mutex_init(&dev->i2c_bus_lock);
+
+       /* register i2c bus 0 */
+       retval = em28xx_i2c_register(dev, 0);
        if (retval < 0) {
-               em28xx_errdev("%s: em28xx_i2c_register - error [%d]!\n",
+               em28xx_errdev("%s: em28xx_i2c_register bus 0 - error [%d]!\n",
                        __func__, retval);
                goto unregister_dev;
        }
 
+       if (dev->def_i2c_bus) {
+               retval = em28xx_i2c_register(dev, 1);
+               if (retval < 0) {
+                       em28xx_errdev("%s: em28xx_i2c_register bus 1 - error [%d]!\n",
+                               __func__, retval);
+                       goto unregister_dev;
+               }
+       }
+
        /*
         * Default format, used for tvp5150 or saa711x output formats
         */
        return 0;
 
 fail:
-       em28xx_i2c_unregister(dev);
+       if (dev->def_i2c_bus)
+               em28xx_i2c_unregister(dev, 1);
+       em28xx_i2c_unregister(dev, 0);
        v4l2_ctrl_handler_free(&dev->ctrl_handler);
 
 unregister_dev:
 
 static int em28xx_i2c_xfer(struct i2c_adapter *i2c_adap,
                           struct i2c_msg msgs[], int num)
 {
-       struct em28xx *dev = i2c_adap->algo_data;
+       struct em28xx_i2c_bus *i2c_bus = i2c_adap->algo_data;
+       struct em28xx *dev = i2c_bus->dev;
+       unsigned bus = i2c_bus->bus;
        int addr, rc, i, byte;
 
-       if (num <= 0)
+       rc = rt_mutex_trylock(&dev->i2c_bus_lock);
+       if (rc < 0)
+               return rc;
+
+       /* Switch I2C bus if needed */
+       if (bus != dev->cur_i2c_bus) {
+               if (bus == 1)
+                       dev->cur_i2c_bus |= EM2874_I2C_SECONDARY_BUS_SELECT;
+               else
+                       dev->cur_i2c_bus &= ~EM2874_I2C_SECONDARY_BUS_SELECT;
+               em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, dev->cur_i2c_bus);
+               dev->cur_i2c_bus = bus;
+       }
+
+       if (num <= 0) {
+               rt_mutex_unlock(&dev->i2c_bus_lock);
                return 0;
+       }
        for (i = 0; i < num; i++) {
                addr = msgs[i].addr << 1;
                if (i2c_debug)
                        if (rc == -ENODEV) {
                                if (i2c_debug)
                                        printk(" no device\n");
+                               rt_mutex_unlock(&dev->i2c_bus_lock);
                                return rc;
                        }
                } else if (msgs[i].flags & I2C_M_RD) {
                if (rc < 0) {
                        if (i2c_debug)
                                printk(" ERROR: %i\n", rc);
+                       rt_mutex_unlock(&dev->i2c_bus_lock);
                        return rc;
                }
                if (i2c_debug)
                        printk("\n");
        }
 
+       rt_mutex_unlock(&dev->i2c_bus_lock);
        return num;
 }
 
 
 /* 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, u16 addr, bool addr_w16,
-                                u16 len, u8 *data)
+static int em28xx_i2c_read_block(struct em28xx *dev, unsigned bus, u16 addr,
+                                bool addr_w16, u16 len, u8 *data)
 {
        int remain = len, rsize, rsize_max, ret;
        u8 buf[2];
        /* Select address */
        buf[0] = addr >> 8;
        buf[1] = addr & 0xff;
-       ret = i2c_master_send(&dev->i2c_client[dev->def_i2c_bus], buf + !addr_w16, 1 + addr_w16);
+       ret = i2c_master_send(&dev->i2c_client[bus], buf + !addr_w16, 1 + addr_w16);
        if (ret < 0)
                return ret;
        /* Read data */
                else
                        rsize = remain;
 
-               ret = i2c_master_recv(&dev->i2c_client[dev->def_i2c_bus], data, rsize);
+               ret = i2c_master_recv(&dev->i2c_client[bus], data, rsize);
                if (ret < 0)
                        return ret;
 
        return len;
 }
 
-static int em28xx_i2c_eeprom(struct em28xx *dev, u8 **eedata, u16 *eedata_len)
+static int em28xx_i2c_eeprom(struct em28xx *dev, unsigned bus,
+                            u8 **eedata, u16 *eedata_len)
 {
        const u16 len = 256;
        /* FIXME common length/size for bytes to read, to display, hash
        *eedata = NULL;
        *eedata_len = 0;
 
-       dev->i2c_client[dev->def_i2c_bus].addr = 0xa0 >> 1;
+       /* 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[dev->def_i2c_bus], &buf, 0);
+       err = i2c_master_recv(&dev->i2c_client[bus], &buf, 0);
        if (err < 0) {
                em28xx_info("board has no eeprom\n");
                return -ENODEV;
                return -ENOMEM;
 
        /* Read EEPROM content */
-       err = em28xx_i2c_read_block(dev, 0x0000, dev->eeprom_addrwidth_16bit,
+       err = em28xx_i2c_read_block(dev, bus, 0x0000,
+                                   dev->eeprom_addrwidth_16bit,
                                    len, data);
        if (err != len) {
                em28xx_errdev("failed to read eeprom (err=%d)\n", err);
 
                /* Read hardware config dataset offset from address
                 * (microcode start + 46)                           */
-               err = em28xx_i2c_read_block(dev, mc_start + 46, 1, 2, data);
+               err = em28xx_i2c_read_block(dev, bus, mc_start + 46, 1, 2,
+                                           data);
                if (err != 2) {
                        em28xx_errdev("failed to read hardware configuration data from eeprom (err=%d)\n",
                                      err);
                 * the old eeprom and not longer than 256 bytes.
                 * tveeprom is currently also limited to 256 bytes.
                 */
-               err = em28xx_i2c_read_block(dev, hwconf_offset, 1, len, data);
+               err = em28xx_i2c_read_block(dev, bus, hwconf_offset, 1, len,
+                                           data);
                if (err != len) {
                        em28xx_errdev("failed to read hardware configuration data from eeprom (err=%d)\n",
                                      err);
 /*
  * functionality()
  */
-static u32 functionality(struct i2c_adapter *adap)
+static u32 functionality(struct i2c_adapter *i2c_adap)
 {
-       struct em28xx *dev = adap->algo_data;
+       struct em28xx_i2c_bus *i2c_bus = i2c_adap->algo_data;
+       struct em28xx *dev = i2c_bus->dev;
+
        u32 func_flags = I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
        if (dev->board.is_em2800)
                func_flags &= ~I2C_FUNC_SMBUS_WRITE_BLOCK_DATA;
  * do_i2c_scan()
  * check i2c address range for devices
  */
-void em28xx_do_i2c_scan(struct em28xx *dev)
+void em28xx_do_i2c_scan(struct em28xx *dev, unsigned bus)
 {
        u8 i2c_devicelist[128];
        unsigned char buf;
        memset(i2c_devicelist, 0, ARRAY_SIZE(i2c_devicelist));
 
        for (i = 0; i < ARRAY_SIZE(i2c_devs); i++) {
-               dev->i2c_client[dev->def_i2c_bus].addr = i;
-               rc = i2c_master_recv(&dev->i2c_client[dev->def_i2c_bus], &buf, 0);
+               dev->i2c_client[bus].addr = i;
+               rc = i2c_master_recv(&dev->i2c_client[bus], &buf, 0);
                if (rc < 0)
                        continue;
                i2c_devicelist[i] = i;
-               em28xx_info("found i2c device @ 0x%x [%s]\n",
-                           i << 1, i2c_devs[i] ? i2c_devs[i] : "???");
+               em28xx_info("found i2c device @ 0x%x on bus %d [%s]\n",
+                           i << 1, bus, i2c_devs[i] ? i2c_devs[i] : "???");
        }
 
-       dev->i2c_hash = em28xx_hash_mem(i2c_devicelist,
-                                       ARRAY_SIZE(i2c_devicelist), 32);
+       if (bus == dev->def_i2c_bus)
+               dev->i2c_hash = em28xx_hash_mem(i2c_devicelist,
+                                               ARRAY_SIZE(i2c_devicelist), 32);
 }
 
 /*
  * em28xx_i2c_register()
  * register i2c bus
  */
-int em28xx_i2c_register(struct em28xx *dev)
+int em28xx_i2c_register(struct em28xx *dev, unsigned bus)
 {
        int retval;
 
        BUG_ON(!dev->em28xx_write_regs || !dev->em28xx_read_reg);
        BUG_ON(!dev->em28xx_write_regs_req || !dev->em28xx_read_reg_req);
-       dev->i2c_adap[dev->def_i2c_bus] = em28xx_adap_template;
-       dev->i2c_adap[dev->def_i2c_bus].dev.parent = &dev->udev->dev;
-       strcpy(dev->i2c_adap[dev->def_i2c_bus].name, dev->name);
-       dev->i2c_adap[dev->def_i2c_bus].algo_data = dev;
-       i2c_set_adapdata(&dev->i2c_adap[dev->def_i2c_bus], &dev->v4l2_dev);
 
-       retval = i2c_add_adapter(&dev->i2c_adap[dev->def_i2c_bus]);
+       if (bus >= NUM_I2C_BUSES)
+               return -ENODEV;
+
+       dev->i2c_adap[bus] = em28xx_adap_template;
+       dev->i2c_adap[bus].dev.parent = &dev->udev->dev;
+       strcpy(dev->i2c_adap[bus].name, dev->name);
+
+       dev->i2c_bus[bus].bus = bus;
+       dev->i2c_bus[bus].dev = dev;
+       dev->i2c_adap[bus].algo_data = &dev->i2c_bus[bus];
+       i2c_set_adapdata(&dev->i2c_adap[bus], &dev->v4l2_dev);
+
+       retval = i2c_add_adapter(&dev->i2c_adap[bus]);
        if (retval < 0) {
                em28xx_errdev("%s: i2c_add_adapter failed! retval [%d]\n",
                        __func__, retval);
                return retval;
        }
 
-       dev->i2c_client[dev->def_i2c_bus] = em28xx_client_template;
-       dev->i2c_client[dev->def_i2c_bus].adapter = &dev->i2c_adap[dev->def_i2c_bus];
+       dev->i2c_client[bus] = em28xx_client_template;
+       dev->i2c_client[bus].adapter = &dev->i2c_adap[bus];
 
-       retval = em28xx_i2c_eeprom(dev, &dev->eedata, &dev->eedata_len);
-       if ((retval < 0) && (retval != -ENODEV)) {
-               em28xx_errdev("%s: em28xx_i2_eeprom failed! retval [%d]\n",
-                       __func__, retval);
+       /* 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)) {
+                       em28xx_errdev("%s: em28xx_i2_eeprom failed! retval [%d]\n",
+                               __func__, retval);
 
-               return retval;
+                       return retval;
+               }
        }
 
        if (i2c_scan)
-               em28xx_do_i2c_scan(dev);
+               em28xx_do_i2c_scan(dev, bus);
 
        return 0;
 }
  * em28xx_i2c_unregister()
  * unregister i2c_bus
  */
-int em28xx_i2c_unregister(struct em28xx *dev)
+int em28xx_i2c_unregister(struct em28xx *dev, unsigned bus)
 {
-       i2c_del_adapter(&dev->i2c_adap[dev->def_i2c_bus]);
+       if (bus >= NUM_I2C_BUSES)
+               return -ENODEV;
+
+       i2c_del_adapter(&dev->i2c_adap[bus]);
        return 0;
 }