This patch implements the USB part of the Diolan USB-I2C/SPI/GPIO
Master Adapter DLN-2. Details about the device can be found here:

https://www.diolan.com/i2c/i2c_interface.html.

Information about the USB protocol can be found in the Programmer's
Reference Manual [1], see section 1.7.

Because the hardware has a single transmit endpoint and a single
receive endpoint the communication between the various DLN2 drivers
and the hardware will be muxed/demuxed by this driver.

Each DLN2 module will be identified by the handle field within the DLN2
message header. If a DLN2 module issues multiple commands in parallel
they will be identified by the echo counter field in the message header.

The DLN2 modules can use the dln2_transfer() function to issue a
command and wait for its response. They can also register a callback
that is going to be called when a specific event id is generated by
the device (e.g. GPIO interrupts). The device uses handle 0 for
sending events.

[1] https://www.diolan.com/downloads/dln-api-manual.pdf

Signed-off-by: Octavian Purdila <octavian.purd...@intel.com>
---
 drivers/mfd/Kconfig      |   9 +
 drivers/mfd/Makefile     |   1 +
 drivers/mfd/dln2.c       | 653 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mfd/dln2.h |  61 +++++
 4 files changed, 724 insertions(+)
 create mode 100644 drivers/mfd/dln2.c
 create mode 100644 include/linux/mfd/dln2.h

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index de5abf2..7bcf895 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -183,6 +183,15 @@ config MFD_DA9063
          Additional drivers must be enabled in order to use the functionality
          of the device.
 
+config MFD_DLN2
+       tristate "Diolan DLN2 support"
+       select MFD_CORE
+       depends on USB
+       help
+         This adds support for Diolan USB-I2C/SPI/GPIO Master Adapter DLN-2.
+         Additional drivers must be enabled in order to use the functionality
+         of the device.
+
 config MFD_MC13XXX
        tristate
        depends on (SPI_MASTER || I2C)
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index f001487..591988d 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -169,6 +169,7 @@ obj-$(CONFIG_MFD_AS3711)    += as3711.o
 obj-$(CONFIG_MFD_AS3722)       += as3722.o
 obj-$(CONFIG_MFD_STW481X)      += stw481x.o
 obj-$(CONFIG_MFD_IPAQ_MICRO)   += ipaq-micro.o
+obj-$(CONFIG_MFD_DLN2)         += dln2.o
 
 intel-soc-pmic-objs            := intel_soc_pmic_core.o intel_soc_pmic_crc.o
 obj-$(CONFIG_INTEL_SOC_PMIC)   += intel-soc-pmic.o
diff --git a/drivers/mfd/dln2.c b/drivers/mfd/dln2.c
new file mode 100644
index 0000000..81ff58e
--- /dev/null
+++ b/drivers/mfd/dln2.c
@@ -0,0 +1,653 @@
+/*
+ * Driver for the Diolan DLN-2 USB adapter
+ *
+ * Copyright (c) 2014 Intel Corporation
+ *
+ * Derived from:
+ *  i2c-diolan-u2c.c
+ *  Copyright (c) 2010-2011 Ericsson AB
+ *
+ * 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, version 2.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/dln2.h>
+
+#define DRIVER_NAME                    "usb-dln2"
+
+struct dln2_header {
+       __le16 size;
+       __le16 id;
+       __le16 echo;
+       __le16 handle;
+} __packed;
+
+struct dln2_response {
+       struct dln2_header hdr;
+       __le16 result;
+} __packed;
+
+#define DLN2_GENERIC_MODULE_ID         0x00
+#define DLN2_GENERIC_CMD(cmd)          DLN2_CMD(cmd, DLN2_GENERIC_MODULE_ID)
+#define CMD_GET_DEVICE_VER             DLN2_GENERIC_CMD(0x30)
+#define CMD_GET_DEVICE_SN              DLN2_GENERIC_CMD(0x31)
+
+#define DLN2_HW_ID                     0x200
+#define DLN2_USB_TIMEOUT               200     /* in ms */
+#define DLN2_MAX_RX_SLOTS              16
+#define DLN2_MAX_MODULES               5
+#define DLN2_MAX_URBS                  16
+
+#define DLN2_HANDLE_GPIO_EVENT         0
+#define DLN2_HANDLE_CTRL               1
+#define DLN2_HANDLE_GPIO               2
+#define DLN2_HANDLE_I2C                        3
+
+/* Receive context used between the receive demultiplexer and the
+ * transfer routine. While sending a request the transfer routine
+ * will look for a free receive context and use it to wait for a
+ * response and to receive the URB and thus the response data. */
+struct dln2_rx_context {
+       struct completion done;
+       struct urb *urb;
+       bool connected;
+};
+
+/* Receive contexts for a particular DLN2 module (i2c, gpio, etc.). We
+ * use the handle header field to indentify the module in
+ * dln2_dev.mod_rx_slots and then the echo header field to index the
+ * slots field and find the receive context for a particular
+ * request. */
+struct dln2_mod_rx_slots {
+       /* RX slots bitmap */
+       unsigned long bmap;
+
+       /* used to wait for a free RX slot */
+       wait_queue_head_t wq;
+
+       /* used to wait for an RX operation to complete */
+       struct dln2_rx_context slots[DLN2_MAX_RX_SLOTS];
+
+       /* avoid races between free_rx_slot and dln2_rx_transfer_cb */
+       spinlock_t lock;
+};
+
+struct dln2_dev {
+       struct usb_device *usb_dev;
+       struct usb_interface *interface;
+       u8 ep_in;
+       u8 ep_out;
+
+       struct urb *rx_urb[DLN2_MAX_URBS];
+       void *rx_buf[DLN2_MAX_URBS];
+
+       struct dln2_mod_rx_slots mod_rx_slots[DLN2_MAX_MODULES];
+
+       struct list_head rx_cb_list;
+       spinlock_t rx_cb_lock;
+};
+
+static bool find_free_slot(struct dln2_mod_rx_slots *rxs, int *slot)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&rxs->lock, flags);
+
+       *slot = find_first_zero_bit(&rxs->bmap, DLN2_MAX_RX_SLOTS);
+
+       if (*slot < DLN2_MAX_RX_SLOTS) {
+               struct dln2_rx_context *rxc = &rxs->slots[*slot];
+
+               init_completion(&rxc->done);
+               set_bit(*slot, &rxs->bmap);
+               rxc->connected = true;
+       }
+
+       spin_unlock_irqrestore(&rxs->lock, flags);
+
+       return *slot < DLN2_MAX_RX_SLOTS;
+}
+
+static int alloc_rx_slot(struct dln2_mod_rx_slots *rxs)
+{
+       int slot, ret;
+
+       /* No need to timeout here, the wait is bounded by the timeout
+        * in _dln2_transfer */
+       ret = wait_event_interruptible(rxs->wq, find_free_slot(rxs, &slot));
+       if (ret < 0)
+               return ret;
+
+       return slot;
+}
+
+static void free_rx_slot(struct dln2_dev *dln2, struct dln2_mod_rx_slots *rxs,
+                        int slot)
+{
+       struct urb *urb = NULL;
+       unsigned long flags;
+       struct dln2_rx_context *rxc;
+       struct device *dev = &dln2->interface->dev;
+       int ret;
+
+       spin_lock_irqsave(&rxs->lock, flags);
+
+       clear_bit(slot, &rxs->bmap);
+
+       rxc = &rxs->slots[slot];
+       rxc->connected = false;
+       urb = rxc->urb;
+       rxc->urb = NULL;
+
+       spin_unlock_irqrestore(&rxs->lock, flags);
+
+       if (urb)  {
+               ret = usb_submit_urb(urb, GFP_KERNEL);
+               if (ret < 0)
+                       dev_err(dev, "failed to re-submit RX URB: %d\n", ret);
+       }
+
+       wake_up_interruptible(&rxs->wq);
+}
+
+struct dln2_rx_cb_entry {
+       struct list_head list;
+       u16 id;
+       struct platform_device *pdev;
+       dln2_rx_cb_t callback;
+};
+
+int dln2_register_event_cb(struct platform_device *pdev, u16 id,
+                          dln2_rx_cb_t rx_cb)
+{
+       struct dln2_dev *dln2 = dev_get_drvdata(pdev->dev.parent);
+       struct dln2_rx_cb_entry *i, *new;
+       unsigned long flags;
+       int ret = 0;
+
+       new = kmalloc(sizeof(*new), GFP_KERNEL);
+       if (!new)
+               return -ENOMEM;
+
+       new->id = id;
+       new->callback = rx_cb;
+       new->pdev = pdev;
+
+       spin_lock_irqsave(&dln2->rx_cb_lock, flags);
+
+       list_for_each_entry(i, &dln2->rx_cb_list, list) {
+               if (i->id == id) {
+                       ret = -EBUSY;
+                       break;
+               }
+       }
+
+       if (!ret)
+               list_add(&new->list, &dln2->rx_cb_list);
+
+       spin_unlock_irqrestore(&dln2->rx_cb_lock, flags);
+
+       if (ret)
+               kfree(new);
+
+       return ret;
+}
+EXPORT_SYMBOL(dln2_register_event_cb);
+
+void dln2_unregister_event_cb(struct platform_device *pdev, u16 id)
+{
+       struct dln2_dev *dln2 = dev_get_drvdata(pdev->dev.parent);
+       struct dln2_rx_cb_entry *i, *tmp;
+       unsigned long flags;
+
+       spin_lock_irqsave(&dln2->rx_cb_lock, flags);
+
+       list_for_each_entry_safe(i, tmp, &dln2->rx_cb_list, list) {
+               if (i->id == id) {
+                       list_del(&i->list);
+                       kfree(i);
+               }
+       }
+
+       spin_unlock_irqrestore(&dln2->rx_cb_lock, flags);
+}
+EXPORT_SYMBOL(dln2_unregister_event_cb);
+
+static void dln2_rx_transfer(struct dln2_dev *dln2, struct urb *urb,
+                            u16 handle, u16 rx_slot)
+{
+       struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[handle];
+       struct dln2_rx_context *rxc;
+       struct device *dev = &dln2->interface->dev;
+       int err;
+
+       spin_lock(&rxs->lock);
+       rxc = &rxs->slots[rx_slot];
+       if (rxc->connected) {
+               rxc->urb = urb;
+               complete(&rxc->done);
+       } else {
+               dev_warn(dev, "droping response %d/%d", handle, rx_slot);
+               err = usb_submit_urb(urb, GFP_ATOMIC);
+               if (err < 0)
+                       dev_err(dev, "failed to re-submit RX URB: %d\n", err);
+       }
+       spin_unlock(&rxs->lock);
+}
+
+static void dln2_run_rx_callbacks(struct dln2_dev *dln2, u16 id, u16 echo,
+                                 void *data, int len)
+{
+       struct dln2_rx_cb_entry *i;
+
+       spin_lock(&dln2->rx_cb_lock);
+
+       list_for_each_entry(i, &dln2->rx_cb_list, list)
+               if (i->id == id)
+                       i->callback(i->pdev, echo, data, len);
+
+       spin_unlock(&dln2->rx_cb_lock);
+}
+
+static void dln2_rx(struct urb *urb)
+{
+       struct dln2_dev *dln2 = urb->context;
+       struct dln2_header *hdr = urb->transfer_buffer;
+       struct device *dev = &dln2->interface->dev;
+       u16 id, echo, handle, size;
+       u8 *data;
+       int len, err;
+
+       switch (urb->status) {
+       case 0:
+               /* success */
+               break;
+       case -ECONNRESET:
+       case -ENOENT:
+       case -ESHUTDOWN:
+       case -EPIPE:
+               /* this urb is terminated, clean up */
+               dev_dbg(dev, "urb shutting down with status %d\n", urb->status);
+               return;
+       default:
+               dev_dbg(dev, "nonzero urb status received %d\n", urb->status);
+               goto out;
+       }
+
+       if (urb->actual_length < sizeof(struct dln2_header)) {
+               dev_err(dev, "short response: %d\n", urb->actual_length);
+               goto out;
+       }
+
+       handle = le16_to_cpu(hdr->handle);
+       id = le16_to_cpu(hdr->id);
+       echo = le16_to_cpu(hdr->echo);
+       size = le16_to_cpu(hdr->size);
+
+       if (size != urb->actual_length) {
+               dev_err(dev, "size mismatch: handle %x cmd %x echo %x size %d 
actual %d\n",
+                       handle, id, echo, size, urb->actual_length);
+               goto out;
+       }
+
+       if (handle > DLN2_MAX_MODULES) {
+               dev_warn(dev, "RX: invalid handle %d\n", handle);
+               goto out;
+       }
+
+       data = urb->transfer_buffer + sizeof(struct dln2_header);
+       len = urb->actual_length - sizeof(struct dln2_header);
+
+       if (!handle) {
+               dln2_run_rx_callbacks(dln2, id, echo, data, len);
+               err = usb_submit_urb(urb, GFP_ATOMIC);
+               if (err < 0)
+                       goto out_submit_failed;
+       } else {
+               dln2_rx_transfer(dln2, urb, handle, echo);
+       }
+
+       return;
+
+out:
+       err = usb_submit_urb(urb, GFP_ATOMIC);
+out_submit_failed:
+       if (err < 0)
+               dev_err(dev, "failed to re-submit RX URB: %d\n", err);
+}
+
+static void *dln2_prep_buf(u16 handle, u16 cmd, u16 echo, void *obuf,
+                          int *obuf_len, gfp_t gfp)
+{
+       void *buf;
+       int len;
+       struct dln2_header *hdr;
+
+       len = *obuf_len + sizeof(*hdr);
+       buf = kmalloc(len, gfp);
+       if (!buf)
+               return NULL;
+
+       hdr = (struct dln2_header *)buf;
+       hdr->id = cpu_to_le16(cmd);
+       hdr->size = cpu_to_le16(len);
+       hdr->echo = cpu_to_le16(echo);
+       hdr->handle = cpu_to_le16(handle);
+
+       memcpy(buf + sizeof(*hdr), obuf, *obuf_len);
+
+       *obuf_len = len;
+
+       return buf;
+}
+
+static int dln2_send_wait(struct dln2_dev *dln2, u16 handle, u16 cmd, u16 echo,
+                         void *obuf, int obuf_len)
+{
+       int len = obuf_len, ret = 0, actual;
+       void *buf;
+
+       buf = dln2_prep_buf(handle, cmd, echo, obuf, &len, GFP_KERNEL);
+       if (!buf)
+               return -ENOMEM;
+
+       ret = usb_bulk_msg(dln2->usb_dev,
+                          usb_sndbulkpipe(dln2->usb_dev, dln2->ep_out),
+                          buf, len, &actual, DLN2_USB_TIMEOUT);
+
+       kfree(buf);
+
+       return ret;
+}
+
+static int _dln2_transfer(struct dln2_dev *dln2, u16 handle, u16 cmd,
+                         void *obuf, int obuf_len, void *ibuf, int *ibuf_len)
+{
+       u16 result, rx_slot;
+       struct dln2_response *rsp;
+       int ret = 0;
+       const int timeout = DLN2_USB_TIMEOUT * HZ / 1000;
+       struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[handle];
+       struct dln2_rx_context *rxc;
+       struct device *dev = &dln2->interface->dev;
+
+       rx_slot = alloc_rx_slot(rxs);
+       if (rx_slot < 0)
+               return rx_slot;
+
+       ret = dln2_send_wait(dln2, handle, cmd, rx_slot, obuf, obuf_len);
+       if (ret < 0) {
+               free_rx_slot(dln2, rxs, rx_slot);
+               dev_err(dev, "USB write failed: %d", ret);
+               return ret;
+       }
+
+       rxc = &rxs->slots[rx_slot];
+
+       ret = wait_for_completion_interruptible_timeout(&rxc->done, timeout);
+       if (ret <= 0) {
+               ret = !ret ? -ETIMEDOUT : ret;
+               goto out_free_rx_slot;
+       }
+
+       /* if we got here we know that the response header has been checked */
+       rsp = rxc->urb->transfer_buffer;
+       result = le16_to_cpu(rsp->result);
+
+       if (result) {
+               dev_dbg(dev, "%d received response with error %d\n",
+                       handle, result);
+               ret = -EREMOTEIO;
+               goto out_free_rx_slot;
+       }
+
+       if (!ibuf) {
+               ret = 0;
+               goto out_free_rx_slot;
+       }
+
+       if (*ibuf_len > rxc->urb->actual_length - sizeof(*rsp))
+               *ibuf_len = rxc->urb->actual_length - sizeof(*rsp);
+
+       memcpy(ibuf, rsp + 1, *ibuf_len);
+
+out_free_rx_slot:
+       free_rx_slot(dln2, rxs, rx_slot);
+
+       return ret;
+}
+
+struct dln2_platform_data {
+       u16 handle;
+};
+
+int dln2_transfer(struct platform_device *pdev, u16 cmd,
+                 void *obuf, int obuf_len, void *ibuf, int *ibuf_len)
+{
+       struct dln2_platform_data *dln2_pdata;
+       struct dln2_dev *dln2;
+       u16 h;
+
+       /* USB device has been disconnected, bail out */
+       if (!pdev)
+               return -ENODEV;
+
+       dln2 = dev_get_drvdata(pdev->dev.parent);
+       dln2_pdata = dev_get_platdata(&pdev->dev);
+       h = dln2_pdata->handle;
+
+       return _dln2_transfer(dln2, h, cmd, obuf, obuf_len, ibuf, ibuf_len);
+}
+EXPORT_SYMBOL(dln2_transfer);
+
+static int dln2_check_hw(struct dln2_dev *dln2)
+{
+       __le32 hw_type;
+       int ret, len = sizeof(hw_type);
+
+       ret = _dln2_transfer(dln2, DLN2_HANDLE_CTRL, CMD_GET_DEVICE_VER,
+                            NULL, 0, &hw_type, &len);
+       if (ret < 0)
+               return ret;
+
+       if (le32_to_cpu(hw_type) != DLN2_HW_ID) {
+               dev_err(&dln2->interface->dev, "Device ID 0x%x not supported!",
+                       le32_to_cpu(hw_type));
+               return -ENODEV;
+       }
+
+       return 0;
+}
+
+static int dln2_print_serialno(struct dln2_dev *dln2)
+{
+       __le32 serial_no;
+       int ret, len = sizeof(serial_no);
+       struct device *dev = &dln2->interface->dev;
+
+       ret = _dln2_transfer(dln2, DLN2_HANDLE_CTRL, CMD_GET_DEVICE_SN, NULL, 0,
+                            &serial_no, &len);
+       if (ret < 0)
+               return ret;
+
+       dev_info(dev, "Diolan DLN2 serial 0x%x\n", le32_to_cpu(serial_no));
+
+       return 0;
+}
+
+static int dln2_hw_init(struct dln2_dev *dln2)
+{
+       int ret = dln2_check_hw(dln2);
+
+       if (ret < 0)
+               return ret;
+
+       return dln2_print_serialno(dln2);
+}
+
+static void dln2_free_rx_urbs(struct dln2_dev *dln2)
+{
+       int i;
+
+       for (i = 0; i < DLN2_MAX_URBS; i++) {
+               usb_kill_urb(dln2->rx_urb[i]);
+               usb_free_urb(dln2->rx_urb[i]);
+               kfree(dln2->rx_buf[i]);
+       }
+}
+
+static void dln2_free(struct dln2_dev *dln2)
+{
+       dln2_free_rx_urbs(dln2);
+       usb_put_dev(dln2->usb_dev);
+       kfree(dln2);
+}
+
+static int dln2_setup_rx_urbs(struct dln2_dev *dln2,
+                             struct usb_host_interface *hostif)
+{
+       int i, ret;
+       int rx_max_size = le16_to_cpu(hostif->endpoint[1].desc.wMaxPacketSize);
+       struct device *dev = &dln2->interface->dev;
+
+       for (i = 0; i < DLN2_MAX_URBS; i++) {
+               dln2->rx_buf[i] = kmalloc(rx_max_size, GFP_KERNEL);
+               if (!dln2->rx_buf[i])
+                       return -ENOMEM;
+
+               dln2->rx_urb[i] = usb_alloc_urb(0, GFP_KERNEL);
+               if (!dln2->rx_urb[i])
+                       return -ENOMEM;
+
+               usb_fill_bulk_urb(dln2->rx_urb[i], dln2->usb_dev,
+                                 usb_rcvbulkpipe(dln2->usb_dev, dln2->ep_in),
+                                 dln2->rx_buf[i], rx_max_size, dln2_rx, dln2);
+
+               ret = usb_submit_urb(dln2->rx_urb[i], GFP_KERNEL);
+               if (ret < 0) {
+                       dev_err(dev, "failed to submit RX URB: %d\n", ret);
+                       return ret;
+               }
+       }
+
+       return 0;
+}
+
+static struct dln2_platform_data dln2_pdata_gpio = {
+       .handle = DLN2_HANDLE_GPIO,
+};
+
+static struct dln2_platform_data dln2_pdata_i2c = {
+       .handle = DLN2_HANDLE_I2C,
+};
+
+static const struct mfd_cell dln2_devs[] = {
+       {
+               .name   = "dln2-gpio",
+               .platform_data = &dln2_pdata_gpio,
+               .pdata_size = sizeof(struct dln2_platform_data),
+       },
+       {
+               .name   = "dln2-i2c",
+               .platform_data = &dln2_pdata_i2c,
+               .pdata_size = sizeof(struct dln2_platform_data),
+       },
+};
+
+static void dln2_disconnect(struct usb_interface *interface)
+{
+       struct dln2_dev *dln2 = usb_get_intfdata(interface);
+
+       mfd_remove_devices(&interface->dev);
+       dln2_free(dln2);
+}
+
+static int dln2_probe(struct usb_interface *interface,
+                     const struct usb_device_id *id)
+{
+       struct usb_host_interface *hostif = interface->cur_altsetting;
+       struct device *dev = &interface->dev;
+       struct dln2_dev *dln2;
+       int ret, i;
+
+       if (hostif->desc.bInterfaceNumber != 0 ||
+           hostif->desc.bNumEndpoints < 2)
+               return -ENODEV;
+
+       dln2 = kzalloc(sizeof(*dln2), GFP_KERNEL);
+       if (!dln2) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
+       dln2->ep_out = hostif->endpoint[0].desc.bEndpointAddress;
+       dln2->ep_in = hostif->endpoint[1].desc.bEndpointAddress;
+       dln2->usb_dev = usb_get_dev(interface_to_usbdev(interface));
+       dln2->interface = interface;
+       usb_set_intfdata(interface, dln2);
+
+       for (i = 0; i < DLN2_MAX_MODULES; i++) {
+               init_waitqueue_head(&dln2->mod_rx_slots[i].wq);
+               spin_lock_init(&dln2->mod_rx_slots[i].lock);
+       }
+
+       spin_lock_init(&dln2->rx_cb_lock);
+       INIT_LIST_HEAD(&dln2->rx_cb_list);
+
+       ret = dln2_setup_rx_urbs(dln2, hostif);
+       if (ret) {
+               dln2_disconnect(interface);
+               return ret;
+       }
+
+       ret = dln2_hw_init(dln2);
+       if (ret < 0) {
+               dev_err(dev, "failed to initialize hardware\n");
+               goto out_cleanup;
+       }
+
+       ret = mfd_add_devices(dev, -1, dln2_devs, ARRAY_SIZE(dln2_devs),
+                             NULL, 0, NULL);
+       if (ret != 0) {
+               dev_err(dev, "Failed to add mfd devices to core.\n");
+               goto out_cleanup;
+       }
+
+       return 0;
+
+out_cleanup:
+       dln2_free(dln2);
+out:
+       return ret;
+}
+
+static const struct usb_device_id dln2_table[] = {
+       { USB_DEVICE(0xa257, 0x2013) },
+       { }
+};
+
+MODULE_DEVICE_TABLE(usb, dln2_table);
+
+static struct usb_driver dln2_driver = {
+       .name = DRIVER_NAME,
+       .probe = dln2_probe,
+       .disconnect = dln2_disconnect,
+       .id_table = dln2_table,
+};
+
+module_usb_driver(dln2_driver);
+
+MODULE_AUTHOR("Octavian Purdila <octavian.purd...@intel.com>");
+MODULE_DESCRIPTION(DRIVER_NAME " driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/mfd/dln2.h b/include/linux/mfd/dln2.h
new file mode 100644
index 0000000..731bf32
--- /dev/null
+++ b/include/linux/mfd/dln2.h
@@ -0,0 +1,61 @@
+#ifndef __LINUX_USB_DLN2_H
+#define __LINUX_USB_DLN2_H
+
+#define DLN2_CMD(cmd, id)              ((cmd) | ((id) << 8))
+
+/**
+ * dln2_rx_cb - event callback function signature
+ *
+ * @pdev - the sub-device that registered this callback
+ * @echo - the echo header field received in the message
+ * @data - the data payload
+ * @len  - the data playload length
+ *
+ * The callback function is called in interrupt context and the data
+ * payload is only valid during the call. If the user needs later
+ * access of the data, it must copy it.
+ */
+
+typedef void (*dln2_rx_cb_t)(struct platform_device *pdev, u16 echo,
+                            const void *data, int len);
+
+/**
+ * dl2n_register_event_cb - register a callback function for an event
+ *
+ * @pdev - the sub-device that registers the callback
+ * @event - the event for which to register a callback
+ * @rx_cb - the callback function
+ *
+ * @return 0 in case of success, negative value in case of error
+ */
+int dln2_register_event_cb(struct platform_device *pdev, u16 event,
+                          dln2_rx_cb_t rx_cb);
+
+/**
+ * dln2_unregister_event_cb - unregister the callback function for an event
+ *
+ * @pdev - the sub-device that registered the callback
+ * @event - the event for which to register a callback
+ */
+void dln2_unregister_event_cb(struct platform_device *pdev, u16 event);
+
+/**
+ * dln2_transfer - issue a DLN2 command and wait for a response and
+ * the associated data
+ *
+ * @pdev - the sub-device which is issueing this transfer
+ * @cmd - the command to be sent to the device
+ * @obuf - the buffer to be sent to the device; can be NULL if the
+ * user doesn't need to transmit data with this command
+ * @obuf_len - the size of the buffer to be sent to the device
+ * @ibuf - any data associated with the response will be copied here;
+ * it can be NULL if the user doesn't need the response data
+ * @ibuf_len - must be initialized to the input buffer size; it will
+ * be modified to indicate the actual data transfered
+ *
+ * @returns 0 for success, negative value for errors
+ */
+int dln2_transfer(struct platform_device *pdev, u16 cmd,
+                 void *obuf, int obuf_len, void *ibuf, int *ibuf_len);
+
+#endif
-- 
1.9.1

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