[PATCH v9 1/4] mfd: add support for Diolan DLN-2 devices

[Octavian Purdila]

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.purdila@xxxxxxxxx>
---
 drivers/mfd/Kconfig      |  11 +
 drivers/mfd/Makefile     |   1 +
 drivers/mfd/dln2.c       | 761 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mfd/dln2.h | 103 +++++++
 4 files changed, 876 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 c9200d3..4538815a 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -189,6 +189,17 @@ 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 such as I2C_DLN2, GPIO_DLN2,
+	  etc. 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 61f8dbf..2cd7e74 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -175,6 +175,7 @@ obj-$(CONFIG_MFD_STW481X)	+= stw481x.o
 obj-$(CONFIG_MFD_IPAQ_MICRO)	+= ipaq-micro.o
 obj-$(CONFIG_MFD_MENF21BMC)	+= menf21bmc.o
 obj-$(CONFIG_MFD_HI6421_PMIC)	+= hi6421-pmic-core.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..b3946ef
--- /dev/null
+++ b/drivers/mfd/dln2.c
@@ -0,0 +1,761 @@
+/*
+ * 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/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>
+#include <linux/rculist.h>
+
+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_URBS			16
+#define DLN2_RX_BUF_SIZE		512
+
+enum dln2_handle {
+	DLN2_HANDLE_EVENT = 0,		/* don't change, hardware defined */
+	DLN2_HANDLE_CTRL,
+	DLN2_HANDLE_GPIO,
+	DLN2_HANDLE_I2C,
+	DLN2_HANDLES
+};
+
+/*
+ * 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 {
+	/* completion used to wait for a response */
+	struct completion done;
+
+	/* if non-NULL the URB contains the response */
+	struct urb *urb;
+
+	/* if true then this context is used to wait for a response */
+	bool in_use;
+};
+
+/*
+ * Receive contexts for a particular DLN2 module (i2c, gpio, etc.). We use the
+ * handle header field to identify 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 */
+	DECLARE_BITMAP(bmap, DLN2_MAX_RX_SLOTS);
+
+	/* 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 alloc/free_rx_slot and dln2_rx_transfer */
+	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_HANDLES];
+
+	struct list_head event_cb_list;
+	spinlock_t event_cb_lock;
+
+	bool disconnect;
+	int active_transfers;
+	wait_queue_head_t disconnect_wq;
+	spinlock_t disconnect_lock;
+};
+
+struct dln2_event_cb_entry {
+	struct list_head list;
+	u16 id;
+	struct platform_device *pdev;
+	dln2_event_cb_t callback;
+};
+
+int dln2_register_event_cb(struct platform_device *pdev, u16 id,
+			   dln2_event_cb_t event_cb)
+{
+	struct dln2_dev *dln2 = dev_get_drvdata(pdev->dev.parent);
+	struct dln2_event_cb_entry *i, *entry;
+	unsigned long flags;
+	int ret = 0;
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->id = id;
+	entry->callback = event_cb;
+	entry->pdev = pdev;
+
+	spin_lock_irqsave(&dln2->event_cb_lock, flags);
+
+	list_for_each_entry(i, &dln2->event_cb_list, list) {
+		if (i->id == id) {
+			ret = -EBUSY;
+			break;
+		}
+	}
+
+	if (!ret)
+		list_add_rcu(&entry->list, &dln2->event_cb_list);
+
+	spin_unlock_irqrestore(&dln2->event_cb_lock, flags);
+
+	if (ret)
+		kfree(entry);
+
+	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_event_cb_entry *i;
+	unsigned long flags;
+	bool found = false;
+
+	spin_lock_irqsave(&dln2->event_cb_lock, flags);
+
+	list_for_each_entry(i, &dln2->event_cb_list, list) {
+		if (i->id == id) {
+			list_del_rcu(&i->list);
+			found = true;
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&dln2->event_cb_lock, flags);
+
+	if (found) {
+		synchronize_rcu();
+		kfree(i);
+	}
+}
+EXPORT_SYMBOL(dln2_unregister_event_cb);
+
+/*
+ * Returns true if a valid transfer slot is found. In this case the URB must not
+ * be resubmitted imediately in dln2_rx as we need the data when dln2_transfer
+ * is woke up. It will be resubmitted there.
+ */
+static bool dln2_transfer_complete(struct dln2_dev *dln2, struct urb *urb,
+				   u16 handle, u16 rx_slot)
+{
+	struct device *dev = &dln2->interface->dev;
+	struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[handle];
+	struct dln2_rx_context *rxc;
+	bool valid_slot = false;
+
+	rxc = &rxs->slots[rx_slot];
+
+	/*
+	 * No need to disable interrupts as this lock is not taken in interrupt
+	 * context elsewhere in this driver. This function (or its callers) are
+	 * also not exported to other modules.
+	 */
+	spin_lock(&rxs->lock);
+	if (rxc->in_use && !rxc->urb) {
+		rxc->urb = urb;
+		complete(&rxc->done);
+		valid_slot = true;
+	}
+	spin_unlock(&rxs->lock);
+
+	if (!valid_slot)
+		dev_warn(dev, "bad/late response %d/%d\n", handle, rx_slot);
+
+	return valid_slot;
+}
+
+static void dln2_run_event_callbacks(struct dln2_dev *dln2, u16 id, u16 echo,
+				     void *data, int len)
+{
+	struct dln2_event_cb_entry *i;
+
+	rcu_read_lock();
+
+	list_for_each_entry_rcu(i, &dln2->event_cb_list, list)
+		if (i->id == id)
+			i->callback(i->pdev, echo, data, len);
+
+	rcu_read_unlock();
+}
+
+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;
+	int 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_HANDLES) {
+		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_HANDLE_EVENT) {
+		dln2_run_event_callbacks(dln2, id, echo, data, len);
+	} else {
+		/* URB will be re-submitted in _dln2_transfer (free_rx_slot) */
+		if (dln2_transfer_complete(dln2, urb, handle, echo))
+			return;
+	}
+
+out:
+	err = usb_submit_urb(urb, GFP_ATOMIC);
+	if (err < 0)
+		dev_err(dev, "failed to resubmit RX URB: %d\n", err);
+}
+
+static void *dln2_prep_buf(u16 handle, u16 cmd, u16 echo, const void *obuf,
+			   int *obuf_len, gfp_t gfp)
+{
+	int len;
+	void *buf;
+	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,
+			  const void *obuf, int obuf_len)
+{
+	int ret = 0;
+	int len = obuf_len;
+	void *buf;
+	int actual;
+
+	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 bool find_free_slot(struct dln2_dev *dln2, u16 handle, int *slot)
+{
+	struct dln2_mod_rx_slots *rxs;
+	unsigned long flags;
+
+	if (dln2->disconnect) {
+		*slot = -ENODEV;
+		return true;
+	}
+
+	rxs = &dln2->mod_rx_slots[handle];
+
+	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];
+
+		set_bit(*slot, rxs->bmap);
+		rxc->in_use = true;
+	}
+
+	spin_unlock_irqrestore(&rxs->lock, flags);
+
+	return *slot < DLN2_MAX_RX_SLOTS;
+}
+
+static int alloc_rx_slot(struct dln2_dev *dln2, u16 handle)
+{
+	int ret;
+	int slot;
+
+	/*
+	 * No need to timeout here, the wait is bounded by the timeout in
+	 * _dln2_transfer.
+	 */
+	ret = wait_event_interruptible(dln2->mod_rx_slots[handle].wq,
+				       find_free_slot(dln2, handle, &slot));
+	if (ret < 0)
+		return ret;
+
+	return slot;
+}
+
+static void free_rx_slot(struct dln2_dev *dln2, u16 handle, int slot)
+{
+	struct dln2_mod_rx_slots *rxs;
+	struct urb *urb = NULL;
+	unsigned long flags;
+	struct dln2_rx_context *rxc;
+
+	rxs = &dln2->mod_rx_slots[handle];
+
+	spin_lock_irqsave(&rxs->lock, flags);
+
+	clear_bit(slot, rxs->bmap);
+
+	rxc = &rxs->slots[slot];
+	rxc->in_use = false;
+	urb = rxc->urb;
+	rxc->urb = NULL;
+	reinit_completion(&rxc->done);
+
+	spin_unlock_irqrestore(&rxs->lock, flags);
+
+	if (urb) {
+		int err;
+		struct device *dev = &dln2->interface->dev;
+
+		err = usb_submit_urb(urb, GFP_KERNEL);
+		if (err < 0)
+			dev_err(dev, "failed to resubmit RX URB: %d\n", err);
+	}
+
+	wake_up_interruptible(&rxs->wq);
+}
+
+static int _dln2_transfer(struct dln2_dev *dln2, u16 handle, u16 cmd,
+			  const void *obuf, unsigned obuf_len,
+			  void *ibuf, unsigned *ibuf_len)
+{
+	int ret = 0;
+	int rx_slot;
+	struct dln2_response *rsp;
+	struct dln2_rx_context *rxc;
+	struct device *dev = &dln2->interface->dev;
+	const int timeout = DLN2_USB_TIMEOUT * HZ / 1000;
+	struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[handle];
+
+	spin_lock(&dln2->disconnect_lock);
+	if (!dln2->disconnect)
+		dln2->active_transfers++;
+	else
+		ret = -ENODEV;
+	spin_unlock(&dln2->disconnect_lock);
+
+	if (ret)
+		return ret;
+
+	rx_slot = alloc_rx_slot(dln2, handle);
+	if (rx_slot < 0) {
+		ret = rx_slot;
+		goto out_decr;
+	}
+
+	ret = dln2_send_wait(dln2, handle, cmd, rx_slot, obuf, obuf_len);
+	if (ret < 0) {
+		dev_err(dev, "USB write failed: %d\n", ret);
+		goto out_free_rx_slot;
+	}
+
+	rxc = &rxs->slots[rx_slot];
+
+	ret = wait_for_completion_interruptible_timeout(&rxc->done, timeout);
+	if (ret <= 0) {
+		if (!ret)
+			ret = -ETIMEDOUT;
+		goto out_free_rx_slot;
+	}
+
+	if (dln2->disconnect) {
+		ret = -ENODEV;
+		goto out_free_rx_slot;
+	}
+
+	/* if we got here we know that the response header has been checked */
+	rsp = rxc->urb->transfer_buffer;
+
+	if (rsp->hdr.size < sizeof(*rsp)) {
+		ret = -EPROTO;
+		goto out_free_rx_slot;
+	}
+
+	if (le16_to_cpu(rsp->result) > 0x80) {
+		dev_dbg(dev, "%d received response with error %d\n",
+			handle, le16_to_cpu(rsp->result));
+		ret = -EREMOTEIO;
+		goto out_free_rx_slot;
+	}
+
+	if (!ibuf) {
+		ret = 0;
+		goto out_free_rx_slot;
+	}
+
+	if (*ibuf_len > rsp->hdr.size - sizeof(*rsp))
+		*ibuf_len = rsp->hdr.size - sizeof(*rsp);
+
+	memcpy(ibuf, rsp + 1, *ibuf_len);
+
+out_free_rx_slot:
+	free_rx_slot(dln2, handle, rx_slot);
+out_decr:
+	spin_lock(&dln2->disconnect_lock);
+	dln2->active_transfers--;
+	spin_unlock(&dln2->disconnect_lock);
+	if (dln2->disconnect)
+		wake_up(&dln2->disconnect_wq);
+
+	return ret;
+}
+
+int dln2_transfer(struct platform_device *pdev, u16 cmd,
+		  const void *obuf, unsigned obuf_len,
+		  void *ibuf, unsigned *ibuf_len)
+{
+	struct dln2_platform_data *dln2_pdata;
+	struct dln2_dev *dln2;
+	u16 handle;
+
+	dln2 = dev_get_drvdata(pdev->dev.parent);
+	dln2_pdata = dev_get_platdata(&pdev->dev);
+	handle = dln2_pdata->handle;
+
+	return _dln2_transfer(dln2, handle, cmd, obuf, obuf_len, ibuf,
+			      ibuf_len);
+}
+EXPORT_SYMBOL(dln2_transfer);
+
+static int dln2_check_hw(struct dln2_dev *dln2)
+{
+	int ret;
+	__le32 hw_type;
+	int 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 (len < sizeof(hw_type))
+		return -EREMOTEIO;
+
+	if (le32_to_cpu(hw_type) != DLN2_HW_ID) {
+		dev_err(&dln2->interface->dev, "Device ID 0x%x not supported\n",
+			le32_to_cpu(hw_type));
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int dln2_print_serialno(struct dln2_dev *dln2)
+{
+	int ret;
+	__le32 serial_no;
+	int 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;
+	if (len < sizeof(serial_no))
+		return -EREMOTEIO;
+
+	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;
+
+	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;
+	const int rx_max_size = DLN2_RX_BUF_SIZE;
+
+	for (i = 0; i < DLN2_MAX_URBS; i++) {
+		int ret;
+		struct device *dev = &dln2->interface->dev;
+
+		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,
+};
+
+/* Only one I2C port seems to be supported on current hardware */
+static struct dln2_platform_data dln2_pdata_i2c = {
+	.handle = DLN2_HANDLE_I2C,
+	.port = 0,
+};
+
+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);
+	int i, j;
+
+	/* don't allow starting new transfers */
+	spin_lock(&dln2->disconnect_lock);
+	dln2->disconnect = true;
+	spin_unlock(&dln2->disconnect_lock);
+
+	/* cancel in progress transfers */
+	for (i = 0; i < DLN2_HANDLES; i++) {
+		struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[i];
+		unsigned long flags;
+
+		spin_lock_irqsave(&rxs->lock, flags);
+
+		/* cancel all response waiters */
+		for (j = 0; j < DLN2_MAX_RX_SLOTS; j++) {
+			struct dln2_rx_context *rxc = &rxs->slots[j];
+
+			if (rxc->in_use)
+				complete(&rxc->done);
+		}
+
+		spin_unlock_irqrestore(&rxs->lock, flags);
+	}
+
+	/* wait for transfers to end */
+	wait_event(dln2->disconnect_wq, !dln2->active_transfers);
+
+	mfd_remove_devices(&interface->dev);
+
+	dln2_free(dln2);
+}
+
+static int dln2_probe(struct usb_interface *interface,
+		      const struct usb_device_id *usb_id)
+{
+	struct usb_host_interface *hostif = interface->cur_altsetting;
+	struct device *dev = &interface->dev;
+	struct dln2_dev *dln2;
+	int ret;
+	int i, j;
+
+	if (hostif->desc.bInterfaceNumber != 0 ||
+	    hostif->desc.bNumEndpoints < 2)
+		return -ENODEV;
+
+	dln2 = kzalloc(sizeof(*dln2), GFP_KERNEL);
+	if (!dln2)
+		return -ENOMEM;
+
+	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);
+	init_waitqueue_head(&dln2->disconnect_wq);
+
+	for (i = 0; i < DLN2_HANDLES; i++) {
+		init_waitqueue_head(&dln2->mod_rx_slots[i].wq);
+		spin_lock_init(&dln2->mod_rx_slots[i].lock);
+		for (j = 0; j < DLN2_MAX_RX_SLOTS; j++)
+			init_completion(&dln2->mod_rx_slots[i].slots[j].done);
+	}
+
+	spin_lock_init(&dln2->event_cb_lock);
+	spin_lock_init(&dln2->disconnect_lock);
+	INIT_LIST_HEAD(&dln2->event_cb_list);
+
+	ret = dln2_setup_rx_urbs(dln2, hostif);
+	if (ret)
+		goto out_cleanup;
+
+	ret = dln2_hw_init(dln2);
+	if (ret < 0) {
+		dev_err(dev, "failed to initialize hardware\n");
+		goto out_cleanup;
+	}
+
+	ret = mfd_add_hotplug_devices(dev, dln2_devs, ARRAY_SIZE(dln2_devs));
+	if (ret != 0) {
+		dev_err(dev, "failed to add mfd devices to core\n");
+		goto out_cleanup;
+	}
+
+	return 0;
+
+out_cleanup:
+	dln2_free(dln2);
+
+	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 = "dln2",
+	.probe = dln2_probe,
+	.disconnect = dln2_disconnect,
+	.id_table = dln2_table,
+};
+
+module_usb_driver(dln2_driver);
+
+MODULE_AUTHOR("Octavian Purdila <octavian.purdila@xxxxxxxxx>");
+MODULE_DESCRIPTION("Core driver for the Diolan DLN2 interface adapter");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/dln2.h b/include/linux/mfd/dln2.h
new file mode 100644
index 0000000..1d12807
--- /dev/null
+++ b/include/linux/mfd/dln2.h
@@ -0,0 +1,103 @@
+#ifndef __LINUX_USB_DLN2_H
+#define __LINUX_USB_DLN2_H
+
+#define DLN2_CMD(cmd, id)		((cmd) | ((id) << 8))
+
+struct dln2_platform_data {
+	u16 handle;		/* sub-driver handle (internally used only) */
+	u8 port;		/* I2C/SPI port */
+};
+
+/**
+ * dln2_event_cb_t - 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 payload 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_event_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
+ * @event_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_event_cb_t event_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 issuing this transfer
+ * @cmd - the command to be sent to the device
+ * @obuf - the buffer to be sent to the device; it 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;
+ *
+ * @return 0 for success, negative value for errors
+ */
+int dln2_transfer(struct platform_device *pdev, u16 cmd,
+		  const void *obuf, unsigned obuf_len,
+		  void *ibuf, unsigned *ibuf_len);
+
+/**
+ * dln2_transfer_rx - variant of @dln2_transfer() where TX buffer is not needed
+ *
+ * @pdev - the sub-device which is issuing this transfer
+ * @cmd - the command 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;
+ *
+ * @return 0 for success, negative value for errors
+ */
+
+static inline int dln2_transfer_rx(struct platform_device *pdev, u16 cmd,
+				   void *ibuf, unsigned *ibuf_len)
+{
+	return dln2_transfer(pdev, cmd, NULL, 0, ibuf, ibuf_len);
+}
+
+/**
+ * dln2_transfer_tx - variant of @dln2_transfer() where RX buffer is not needed
+ *
+ * @pdev - the sub-device which is issuing this transfer
+ * @cmd - the command to be sent to the device
+ * @obuf - the buffer to be sent to the device; it 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
+ *
+ * @return 0 for success, negative value for errors
+ */
+static inline int dln2_transfer_tx(struct platform_device *pdev, u16 cmd,
+				   const void *obuf, unsigned obuf_len)
+{
+	return dln2_transfer(pdev, cmd, obuf, obuf_len, NULL, NULL);
+}
+
+#endif
-- 
1.9.1

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