Message-Id: <1591899224-3403-5-git-send-email-hemantk@codeaurora.org>
Date:   Thu, 11 Jun 2020 11:13:44 -0700
From:   Hemant Kumar <hemantk@...eaurora.org>
To:     manivannan.sadhasivam@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        jhugo@...eaurora.org, bbhatt@...eaurora.org,
        Hemant Kumar <hemantk@...eaurora.org>
Subject: [PATCH v3 4/4] bus: mhi: clients: Add user space client interface driver

This MHI client driver allows user space clients to transfer
data between MHI device and host using standard file operations.
Device file node is created with format

/dev/mhi_<controller_name>_<mhi_device_name>

Currently it supports loopback client.

Signed-off-by: Hemant Kumar <hemantk@...eaurora.org>
---
 drivers/bus/mhi/Kconfig          |   2 +
 drivers/bus/mhi/Makefile         |   1 +
 drivers/bus/mhi/clients/Kconfig  |  16 +
 drivers/bus/mhi/clients/Makefile |   3 +
 drivers/bus/mhi/clients/uci.c    | 652 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 674 insertions(+)
 create mode 100644 drivers/bus/mhi/clients/Kconfig
 create mode 100644 drivers/bus/mhi/clients/Makefile
 create mode 100644 drivers/bus/mhi/clients/uci.c

diff --git a/drivers/bus/mhi/Kconfig b/drivers/bus/mhi/Kconfig
index 6a217ff..f224be8 100644
--- a/drivers/bus/mhi/Kconfig
+++ b/drivers/bus/mhi/Kconfig
@@ -20,3 +20,5 @@ config MHI_BUS_DEBUG
 	 Enable debugfs support for use with the MHI transport. Allows
 	 reading and/or modifying some values within the MHI controller
 	 for debug and test purposes.
+
+source "drivers/bus/mhi/clients/Kconfig"
diff --git a/drivers/bus/mhi/Makefile b/drivers/bus/mhi/Makefile
index 19e6443..48f6028 100644
--- a/drivers/bus/mhi/Makefile
+++ b/drivers/bus/mhi/Makefile
@@ -1,2 +1,3 @@
 # core layer
 obj-y += core/
+obj-y += clients/
diff --git a/drivers/bus/mhi/clients/Kconfig b/drivers/bus/mhi/clients/Kconfig
new file mode 100644
index 0000000..cd84419
--- /dev/null
+++ b/drivers/bus/mhi/clients/Kconfig
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menu "MHI clients support"
+       depends on MHI_BUS
+
+config MHI_UCI
+       tristate "MHI UCI"
+       depends on MHI_BUS
+       help
+	  MHI based userspace client interface driver is for transferring
+	  data between host and device using standard file operations from
+	  user space. Open, read, write, and close operations are supported
+	  by this driver. Please check mhi_uci_match_table for all supported
+	  channels that are exposed to userspace.
+
+endmenu
diff --git a/drivers/bus/mhi/clients/Makefile b/drivers/bus/mhi/clients/Makefile
new file mode 100644
index 0000000..dd2930c
--- /dev/null
+++ b/drivers/bus/mhi/clients/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_MHI_UCI) +=uci.o
diff --git a/drivers/bus/mhi/clients/uci.c b/drivers/bus/mhi/clients/uci.c
new file mode 100644
index 0000000..8f36fb0
--- /dev/null
+++ b/drivers/bus/mhi/clients/uci.c
@@ -0,0 +1,652 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.*/
+
+#include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mhi.h>
+#include <linux/poll.h>
+
+#define DEVICE_NAME "mhi"
+#define MHI_UCI_DRIVER_NAME "mhi_uci"
+#define MAX_UCI_DEVICES (64)
+
+struct uci_chan {
+	wait_queue_head_t wq;
+
+	/* locks ul/dl uci device channel */
+	spinlock_t lock;
+
+	 /* user space waiting to read */
+	struct list_head pending;
+
+	 /* current buffer user space reading */
+	struct uci_buf *cur_buf;
+	size_t rx_size;
+};
+
+struct uci_buf {
+	void *data;
+	size_t len;
+	struct list_head node;
+};
+
+struct mhi_uci_drv {
+	struct list_head head;
+
+	/* uci driver lock to sync open, probe and remove */
+	struct mutex lock;
+	struct class *class;
+	int major;
+	dev_t dev_t;
+};
+
+struct uci_dev {
+	struct list_head node;
+	dev_t devt;
+	struct device *dev;
+	struct mhi_device *mhi_dev;
+	const char *chan;
+
+	/* sync open and close */
+	struct mutex mutex;
+	struct uci_chan ul_chan;
+	struct uci_chan dl_chan;
+	size_t mtu;
+
+	/* maximum size of incoming buffer */
+	size_t actual_mtu;
+	int ref_count;
+	bool enabled;
+};
+
+static DECLARE_BITMAP(uci_minors, MAX_UCI_DEVICES);
+static struct mhi_uci_drv mhi_uci_drv;
+
+static int mhi_queue_inbound(struct uci_dev *uci_dev)
+{
+	struct mhi_device *mhi_dev = uci_dev->mhi_dev;
+	struct device *dev = &mhi_dev->dev;
+	int nr_trbs = mhi_get_no_free_descriptors(mhi_dev, DMA_FROM_DEVICE);
+	size_t mtu = uci_dev->mtu;
+	size_t actual_mtu = uci_dev->actual_mtu;
+	void *buf;
+	struct uci_buf *uci_buf;
+	int ret = -EIO, i;
+
+	for (i = 0; i < nr_trbs; i++) {
+		buf = kmalloc(mtu, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+
+		uci_buf = buf + actual_mtu;
+		uci_buf->data = buf;
+
+		dev_dbg(dev, "Allocated buf %d of %d size %ld\n", i, nr_trbs,
+			actual_mtu);
+
+		ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, buf, actual_mtu,
+				    MHI_EOT);
+		if (ret) {
+			kfree(buf);
+			dev_err(dev, "Failed to queue buffer %d\n", i);
+			return ret;
+		}
+	}
+
+	return ret;
+}
+
+static int mhi_uci_release(struct inode *inode, struct file *file)
+{
+	struct uci_dev *uci_dev = file->private_data;
+
+	mutex_lock(&uci_dev->mutex);
+	uci_dev->ref_count--;
+	if (!uci_dev->ref_count) {
+		struct uci_buf *itr, *tmp;
+		struct uci_chan *uci_chan;
+
+		if (uci_dev->enabled)
+			mhi_unprepare_from_transfer(uci_dev->mhi_dev);
+
+		/* clean inbound channel */
+		uci_chan = &uci_dev->dl_chan;
+		list_for_each_entry_safe(itr, tmp, &uci_chan->pending, node) {
+			list_del(&itr->node);
+			kfree(itr->data);
+		}
+		if (uci_chan->cur_buf)
+			kfree(uci_chan->cur_buf->data);
+
+		uci_chan->cur_buf = NULL;
+
+		if (!uci_dev->enabled) {
+			mutex_unlock(&uci_dev->mutex);
+			mutex_destroy(&uci_dev->mutex);
+			clear_bit(MINOR(uci_dev->devt), uci_minors);
+			kfree(uci_dev);
+			return 0;
+		}
+	}
+
+	mutex_unlock(&uci_dev->mutex);
+
+	return 0;
+}
+
+static __poll_t mhi_uci_poll(struct file *file, poll_table *wait)
+{
+	struct uci_dev *uci_dev = file->private_data;
+	struct mhi_device *mhi_dev = uci_dev->mhi_dev;
+	struct device *dev = &mhi_dev->dev;
+	struct uci_chan *uci_chan;
+	__poll_t mask = 0;
+
+	poll_wait(file, &uci_dev->dl_chan.wq, wait);
+	poll_wait(file, &uci_dev->ul_chan.wq, wait);
+
+	uci_chan = &uci_dev->dl_chan;
+	spin_lock_bh(&uci_chan->lock);
+	if (!uci_dev->enabled) {
+		mask = EPOLLERR;
+	} else {
+		if (!list_empty(&uci_chan->pending) || uci_chan->cur_buf) {
+			dev_dbg(dev, "Client can read from node\n");
+			mask |= EPOLLIN | EPOLLRDNORM;
+		}
+	}
+	spin_unlock_bh(&uci_chan->lock);
+
+	uci_chan = &uci_dev->ul_chan;
+	spin_lock_bh(&uci_chan->lock);
+	if (!uci_dev->enabled) {
+		mask |= EPOLLERR;
+	} else if (mhi_get_no_free_descriptors(mhi_dev, DMA_TO_DEVICE) > 0) {
+		dev_dbg(dev, "Client can write to node\n");
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	}
+	spin_unlock_bh(&uci_chan->lock);
+
+	dev_dbg(dev, "Client attempted to poll, returning mask 0x%x\n", mask);
+
+	return mask;
+}
+
+static ssize_t mhi_uci_write(struct file *file,
+			     const char __user *buf,
+			     size_t count,
+			     loff_t *offp)
+{
+	struct uci_dev *uci_dev = file->private_data;
+	struct mhi_device *mhi_dev = uci_dev->mhi_dev;
+	struct device *dev = &mhi_dev->dev;
+	struct uci_chan *uci_chan = &uci_dev->ul_chan;
+	size_t bytes_xfered = 0;
+	int ret, nr_avail;
+
+	if (!buf || !count)
+		return -EINVAL;
+
+	/* confirm channel is active */
+	spin_lock_bh(&uci_chan->lock);
+	if (!uci_dev->enabled) {
+		spin_unlock_bh(&uci_chan->lock);
+		return -ERESTARTSYS;
+	}
+
+	dev_dbg(dev, "Enter: to xfer:%lu bytes\n", count);
+
+	while (count) {
+		size_t xfer_size;
+		void *kbuf;
+		enum mhi_flags flags;
+
+		spin_unlock_bh(&uci_chan->lock);
+
+		/* wait for free descriptors */
+		ret = wait_event_interruptible(uci_chan->wq,
+					       (!uci_dev->enabled) ||
+				(nr_avail = mhi_get_no_free_descriptors(mhi_dev,
+					       DMA_TO_DEVICE)) > 0);
+
+		if (ret == -ERESTARTSYS || !uci_dev->enabled) {
+			dev_dbg(dev, "Exit signal caught for node or not enabled\n");
+			return -ERESTARTSYS;
+		}
+
+		xfer_size = min_t(size_t, count, uci_dev->mtu);
+		kbuf = kmalloc(xfer_size, GFP_KERNEL);
+		if (!kbuf)
+			return -ENOMEM;
+
+		ret = copy_from_user(kbuf, buf, xfer_size);
+		if (unlikely(ret)) {
+			kfree(kbuf);
+			return ret;
+		}
+
+		spin_lock_bh(&uci_chan->lock);
+
+		/* if ring is full after this force EOT */
+		if (nr_avail > 1 && (count - xfer_size))
+			flags = MHI_CHAIN;
+		else
+			flags = MHI_EOT;
+
+		if (uci_dev->enabled)
+			ret = mhi_queue_buf(mhi_dev, DMA_TO_DEVICE, kbuf,
+					    xfer_size, flags);
+		else
+			ret = -ERESTARTSYS;
+
+		if (ret) {
+			kfree(kbuf);
+			goto sys_interrupt;
+		}
+
+		bytes_xfered += xfer_size;
+		count -= xfer_size;
+		buf += xfer_size;
+	}
+
+	spin_unlock_bh(&uci_chan->lock);
+	dev_dbg(dev, "Exit: Number of bytes xferred:%lu\n", bytes_xfered);
+
+	return bytes_xfered;
+
+sys_interrupt:
+	spin_unlock_bh(&uci_chan->lock);
+
+	return ret;
+}
+
+static ssize_t mhi_uci_read(struct file *file,
+			    char __user *buf,
+			    size_t count,
+			    loff_t *ppos)
+{
+	struct uci_dev *uci_dev = file->private_data;
+	struct mhi_device *mhi_dev = uci_dev->mhi_dev;
+	struct uci_chan *uci_chan = &uci_dev->dl_chan;
+	struct device *dev = &mhi_dev->dev;
+	struct uci_buf *uci_buf;
+	char *ptr;
+	size_t to_copy;
+	int ret = 0;
+
+	if (!buf)
+		return -EINVAL;
+
+	dev_dbg(dev, "Client provided buf len:%lu\n", count);
+
+	mutex_lock(&uci_dev->mutex);
+	/* confirm channel is active */
+	spin_lock_bh(&uci_chan->lock);
+	if (!uci_dev->enabled) {
+		spin_unlock_bh(&uci_chan->lock);
+		mutex_unlock(&uci_dev->mutex);
+		return -ERESTARTSYS;
+	}
+
+	/* No data available to read, wait */
+	if (!uci_chan->cur_buf && list_empty(&uci_chan->pending)) {
+		dev_dbg(dev, "No data available to read waiting\n");
+
+		spin_unlock_bh(&uci_chan->lock);
+		mutex_unlock(&uci_dev->mutex);
+		ret = wait_event_interruptible(uci_chan->wq,
+					       (!uci_dev->enabled ||
+					      !list_empty(&uci_chan->pending)));
+		if (ret == -ERESTARTSYS) {
+			dev_dbg(dev, "Exit signal caught for node\n");
+			return -ERESTARTSYS;
+		}
+
+		mutex_lock(&uci_dev->mutex);
+		spin_lock_bh(&uci_chan->lock);
+		if (!uci_dev->enabled) {
+			dev_dbg(dev, "node is disabled\n");
+			ret = -ERESTARTSYS;
+			goto read_error;
+		}
+	}
+
+	/* new read, get the next descriptor from the list */
+	if (!uci_chan->cur_buf) {
+		uci_buf = list_first_entry_or_null(&uci_chan->pending,
+						   struct uci_buf, node);
+		if (unlikely(!uci_buf)) {
+			ret = -EIO;
+			goto read_error;
+		}
+
+		list_del(&uci_buf->node);
+		uci_chan->cur_buf = uci_buf;
+		uci_chan->rx_size = uci_buf->len;
+		dev_dbg(dev, "Got pkt of size:%zu\n", uci_chan->rx_size);
+	}
+
+	uci_buf = uci_chan->cur_buf;
+
+	/* Copy the buffer to user space */
+	to_copy = min_t(size_t, count, uci_chan->rx_size);
+	ptr = uci_buf->data + (uci_buf->len - uci_chan->rx_size);
+	spin_unlock_bh(&uci_chan->lock);
+
+	ret = copy_to_user(buf, ptr, to_copy);
+	if (ret)
+		goto err_unlock_mtx;
+
+	spin_lock_bh(&uci_chan->lock);
+
+	dev_dbg(dev, "Copied %lu of %lu bytes\n", to_copy, uci_chan->rx_size);
+	uci_chan->rx_size -= to_copy;
+
+	/* we finished with this buffer, queue it back to hardware */
+	if (!uci_chan->rx_size) {
+		uci_chan->cur_buf = NULL;
+
+		if (uci_dev->enabled)
+			ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE,
+					    uci_buf->data,
+					    uci_dev->actual_mtu, MHI_EOT);
+		else
+			ret = -ERESTARTSYS;
+
+		if (ret) {
+			dev_err(dev, "Failed to recycle element\n");
+			kfree(uci_buf->data);
+			goto read_error;
+		}
+	}
+	spin_unlock_bh(&uci_chan->lock);
+	mutex_unlock(&uci_dev->mutex);
+
+	dev_dbg(dev, "Returning %lu bytes\n", to_copy);
+
+	return to_copy;
+
+read_error:
+	spin_unlock_bh(&uci_chan->lock);
+err_unlock_mtx:
+	mutex_unlock(&uci_dev->mutex);
+	return ret;
+}
+
+static int mhi_uci_open(struct inode *inode, struct file *filp)
+{
+	struct uci_dev *uci_dev = NULL, *tmp_dev;
+	int ret = -EIO;
+	struct uci_buf *buf_itr, *tmp;
+	struct uci_chan *dl_chan;
+	struct mhi_device *mhi_dev;
+	struct device *dev;
+
+	mutex_lock(&mhi_uci_drv.lock);
+	list_for_each_entry(tmp_dev, &mhi_uci_drv.head, node) {
+		if (tmp_dev->devt == inode->i_rdev) {
+			uci_dev = tmp_dev;
+			break;
+		}
+	}
+
+	/* could not find a minor node */
+	if (!uci_dev)
+		goto error_exit;
+
+	mhi_dev = uci_dev->mhi_dev;
+	dev = &mhi_dev->dev;
+
+	mutex_lock(&uci_dev->mutex);
+	if (!uci_dev->enabled) {
+		dev_info(dev, "Node exist, but not in active state!\n");
+		goto error_open_chan;
+	}
+
+	uci_dev->ref_count++;
+
+	dev_dbg(dev, "Node open, ref counts %u\n", uci_dev->ref_count);
+
+	if (uci_dev->ref_count == 1) {
+		dev_dbg(dev, "Starting channel\n");
+		ret = mhi_prepare_for_transfer(uci_dev->mhi_dev);
+		if (ret) {
+			dev_err(dev, "Error starting transfer channels\n");
+			uci_dev->ref_count--;
+			goto error_open_chan;
+		}
+
+		ret = mhi_queue_inbound(uci_dev);
+		if (ret)
+			goto error_rx_queue;
+	}
+
+	filp->private_data = uci_dev;
+	mutex_unlock(&uci_dev->mutex);
+	mutex_unlock(&mhi_uci_drv.lock);
+
+	return 0;
+
+error_rx_queue:
+	dl_chan = &uci_dev->dl_chan;
+	mhi_unprepare_from_transfer(uci_dev->mhi_dev);
+	list_for_each_entry_safe(buf_itr, tmp, &dl_chan->pending, node) {
+		list_del(&buf_itr->node);
+		kfree(buf_itr->data);
+	}
+
+error_open_chan:
+	mutex_unlock(&uci_dev->mutex);
+
+error_exit:
+	mutex_unlock(&mhi_uci_drv.lock);
+
+	return ret;
+}
+
+static const struct file_operations mhidev_fops = {
+	.owner = THIS_MODULE,
+	.open = mhi_uci_open,
+	.release = mhi_uci_release,
+	.read = mhi_uci_read,
+	.write = mhi_uci_write,
+	.poll = mhi_uci_poll,
+};
+
+static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev,
+			   struct mhi_result *mhi_result)
+{
+	struct uci_dev *uci_dev = dev_get_drvdata(&mhi_dev->dev);
+	struct uci_chan *uci_chan = &uci_dev->ul_chan;
+	struct device *dev = &mhi_dev->dev;
+
+	dev_dbg(dev, "status:%d xfer_len:%zu\n", mhi_result->transaction_status,
+		mhi_result->bytes_xferd);
+
+	kfree(mhi_result->buf_addr);
+	if (!mhi_result->transaction_status)
+		wake_up(&uci_chan->wq);
+}
+
+static void mhi_dl_xfer_cb(struct mhi_device *mhi_dev,
+			   struct mhi_result *mhi_result)
+{
+	struct uci_dev *uci_dev = dev_get_drvdata(&mhi_dev->dev);
+	struct uci_chan *uci_chan = &uci_dev->dl_chan;
+	struct device *dev = &mhi_dev->dev;
+	unsigned long flags;
+	struct uci_buf *buf;
+
+	dev_dbg(dev, "status:%d receive_len:%zu\n",
+		mhi_result->transaction_status, mhi_result->bytes_xferd);
+
+	if (mhi_result->transaction_status == -ENOTCONN) {
+		kfree(mhi_result->buf_addr);
+		return;
+	}
+
+	spin_lock_irqsave(&uci_chan->lock, flags);
+	buf = mhi_result->buf_addr + uci_dev->actual_mtu;
+	buf->data = mhi_result->buf_addr;
+	buf->len = mhi_result->bytes_xferd;
+	list_add_tail(&buf->node, &uci_chan->pending);
+	spin_unlock_irqrestore(&uci_chan->lock, flags);
+
+	wake_up(&uci_chan->wq);
+}
+
+static int mhi_uci_probe(struct mhi_device *mhi_dev,
+			 const struct mhi_device_id *id)
+{
+	struct uci_dev *uci_dev;
+	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
+	struct device *dev = &mhi_dev->dev;
+	int minor;
+	int dir;
+
+	uci_dev = kzalloc(sizeof(*uci_dev), GFP_KERNEL);
+	if (!uci_dev)
+		return -ENOMEM;
+
+	mutex_init(&uci_dev->mutex);
+	uci_dev->mhi_dev = mhi_dev;
+
+	mutex_lock(&uci_dev->mutex);
+	mutex_lock(&mhi_uci_drv.lock);
+
+	minor = find_first_zero_bit(uci_minors, MAX_UCI_DEVICES);
+	if (minor >= MAX_UCI_DEVICES) {
+		mutex_unlock(&mhi_uci_drv.lock);
+		mutex_unlock(&uci_dev->mutex);
+		kfree(uci_dev);
+		return -ENOSPC;
+	}
+
+	uci_dev->devt = MKDEV(mhi_uci_drv.major, minor);
+	uci_dev->dev = device_create(mhi_uci_drv.class, &mhi_dev->dev,
+				     uci_dev->devt, uci_dev,
+				     DEVICE_NAME "_%s_%s",
+				     dev_name(mhi_cntrl->cntrl_dev),
+				     mhi_dev->name);
+	set_bit(minor, uci_minors);
+
+	for (dir = 0; dir < 2; dir++) {
+		struct uci_chan *uci_chan = (dir) ?
+			&uci_dev->ul_chan : &uci_dev->dl_chan;
+		spin_lock_init(&uci_chan->lock);
+		init_waitqueue_head(&uci_chan->wq);
+		INIT_LIST_HEAD(&uci_chan->pending);
+	}
+
+	uci_dev->mtu = min_t(size_t, id->driver_data, MHI_MAX_MTU);
+	uci_dev->actual_mtu = uci_dev->mtu -  sizeof(struct uci_buf);
+	dev_set_drvdata(&mhi_dev->dev, uci_dev);
+	uci_dev->enabled = true;
+
+	list_add(&uci_dev->node, &mhi_uci_drv.head);
+	mutex_unlock(&mhi_uci_drv.lock);
+	mutex_unlock(&uci_dev->mutex);
+
+	dev_info(dev, "channel:%s successfully probed\n", mhi_dev->name);
+
+	return 0;
+};
+
+static void mhi_uci_remove(struct mhi_device *mhi_dev)
+{
+	struct uci_dev *uci_dev = dev_get_drvdata(&mhi_dev->dev);
+	struct device *dev = &mhi_dev->dev;
+
+	dev_dbg(dev, "%s: enter\n", __func__);
+
+	mutex_lock(&mhi_uci_drv.lock);
+	mutex_lock(&uci_dev->mutex);
+
+	/* disable the node */
+	spin_lock_irq(&uci_dev->dl_chan.lock);
+	spin_lock_irq(&uci_dev->ul_chan.lock);
+	uci_dev->enabled = false;
+	spin_unlock_irq(&uci_dev->ul_chan.lock);
+	spin_unlock_irq(&uci_dev->dl_chan.lock);
+	wake_up(&uci_dev->dl_chan.wq);
+	wake_up(&uci_dev->ul_chan.wq);
+
+	/* delete the node to prevent new opens */
+	device_destroy(mhi_uci_drv.class, uci_dev->devt);
+	uci_dev->dev = NULL;
+	list_del(&uci_dev->node);
+
+	/* safe to free memory only if all file nodes are closed */
+	if (!uci_dev->ref_count) {
+		mutex_unlock(&uci_dev->mutex);
+		mutex_destroy(&uci_dev->mutex);
+		clear_bit(MINOR(uci_dev->devt), uci_minors);
+		dev_set_drvdata(&mhi_dev->dev, NULL);
+		kfree(uci_dev);
+		mutex_unlock(&mhi_uci_drv.lock);
+		return;
+	}
+
+	mutex_unlock(&uci_dev->mutex);
+	mutex_unlock(&mhi_uci_drv.lock);
+
+	dev_dbg(dev, "%s: exit\n", __func__);
+}
+
+/* .driver_data stores max mtu */
+static const struct mhi_device_id mhi_uci_match_table[] = {
+	{ .chan = "LOOPBACK", .driver_data = 0x1000 },
+	{},
+};
+MODULE_DEVICE_TABLE(mhi, mhi_uci_match_table);
+
+static struct mhi_driver mhi_uci_driver = {
+	.id_table = mhi_uci_match_table,
+	.remove = mhi_uci_remove,
+	.probe = mhi_uci_probe,
+	.ul_xfer_cb = mhi_ul_xfer_cb,
+	.dl_xfer_cb = mhi_dl_xfer_cb,
+	.driver = {
+		.name = MHI_UCI_DRIVER_NAME,
+	},
+};
+
+static int mhi_uci_init(void)
+{
+	int ret;
+
+	ret = register_chrdev(0, MHI_UCI_DRIVER_NAME, &mhidev_fops);
+	if (ret < 0)
+		return ret;
+
+	mhi_uci_drv.major = ret;
+	mhi_uci_drv.class = class_create(THIS_MODULE, MHI_UCI_DRIVER_NAME);
+	if (IS_ERR(mhi_uci_drv.class)) {
+		unregister_chrdev(mhi_uci_drv.major, MHI_UCI_DRIVER_NAME);
+		return -ENODEV;
+	}
+
+	mutex_init(&mhi_uci_drv.lock);
+	INIT_LIST_HEAD(&mhi_uci_drv.head);
+
+	ret = mhi_driver_register(&mhi_uci_driver);
+	if (ret) {
+		class_destroy(mhi_uci_drv.class);
+		unregister_chrdev(mhi_uci_drv.major, MHI_UCI_DRIVER_NAME);
+	}
+
+	return ret;
+}
+
+static void __exit mhi_uci_exit(void)
+{
+	mhi_driver_unregister(&mhi_uci_driver);
+	class_destroy(mhi_uci_drv.class);
+	unregister_chrdev(mhi_uci_drv.major, MHI_UCI_DRIVER_NAME);
+}
+
+module_init(mhi_uci_init);
+module_exit(mhi_uci_exit);
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MHI UCI Driver");
-- 
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a Linux Foundation Collaborative Project

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