Re: [PATCH v11 4/4] bus: mhi: Add userspace client interface driver

Manivannan Sadhasivam
2020-10-30T10:34:29Z

Hi Hemant,

On Thu, Oct 29, 2020 at 07:45:46PM -0700, Hemant Kumar wrote:
> This MHI client driver allows userspace clients to transfer
> raw data between MHI device and host using standard file operations.
> Driver instantiates UCI device object which is associated to device
> file node. UCI device object instantiates UCI channel object when device
> file node is opened. UCI channel object is used to manage MHI channels
> by calling MHI core APIs for read and write operations. MHI channels
> are started as part of device open(). MHI channels remain in start
> state until last release() is called on UCI device file node. Device
> file node is created with format
>
> /dev/mhi_<controller_name>_<mhi_device_name>
>
> Currently it supports LOOPBACK channel.
>
> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>

Thanks for continuously updating the series based on reviews, now the locking
part looks a _lot_ cleaner than it used to be. I just have one query (inline)
regarding the usage of refcount for uci_chan and uci_dev. Once you fix that,
I think this is good to go in.

Thanks,
Mani

> ---
> drivers/bus/mhi/Kconfig | 13 +
> drivers/bus/mhi/Makefile | 4 +
> drivers/bus/mhi/uci.c | 662 +++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 679 insertions(+)
> create mode 100644 drivers/bus/mhi/uci.c
>
> diff --git a/drivers/bus/mhi/Kconfig b/drivers/bus/mhi/Kconfig
> index e841c10..476cc55 100644
> --- a/drivers/bus/mhi/Kconfig
> +++ b/drivers/bus/mhi/Kconfig
> @@ -20,3 +20,16 @@ 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.
> +
> +config MHI_UCI
> + tristate "MHI UCI"
> + depends on MHI_BUS
> + help
> + MHI based Userspace Client Interface (UCI) driver is used for
> + transferring raw data between host and device using standard file
> + operations from userspace. 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.
> +
> + To compile this driver as a module, choose M here: the module will be
> + called mhi_uci.
> diff --git a/drivers/bus/mhi/Makefile b/drivers/bus/mhi/Makefile
> index 19e6443..80feefb 100644
> --- a/drivers/bus/mhi/Makefile
> +++ b/drivers/bus/mhi/Makefile
> @@ -1,2 +1,6 @@
> # core layer
> obj-y += core/
> +
> +# MHI client
> +mhi_uci-y := uci.o
> +obj-$(CONFIG_MHI_UCI) += mhi_uci.o
> diff --git a/drivers/bus/mhi/uci.c b/drivers/bus/mhi/uci.c
> new file mode 100644
> index 0000000..ea73c08
> --- /dev/null
> +++ b/drivers/bus/mhi/uci.c
> @@ -0,0 +1,662 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.*/
> +
> +#include <linux/kernel.h>
> +#include <linux/mhi.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/poll.h>
> +
> +#define DEVICE_NAME "mhi"
> +#define MHI_UCI_DRIVER_NAME "mhi_uci"
> +#define MAX_UCI_MINORS 128

Prefix MHI for these.

> +
> +static DEFINE_IDR(uci_idr);
> +static DEFINE_MUTEX(uci_drv_mutex);
> +static struct class *uci_dev_class;
> +static int uci_dev_major;
> +
> +/**
> + * struct uci_chan - MHI channel for a UCI device
> + * @udev: associated UCI device object
> + * @ul_wq: wait queue for writer
> + * @write_lock: mutex write lock for ul channel
> + * @dl_wq: wait queue for reader
> + * @read_lock: mutex read lock for dl channel
> + * @dl_pending_lock: spin lock for dl_pending list
> + * @dl_pending: list of dl buffers userspace is waiting to read
> + * @cur_buf: current buffer userspace is reading
> + * @dl_size: size of the current dl buffer userspace is reading
> + * @ref_count: uci_chan reference count
> + */
> +struct uci_chan {
> + struct uci_dev *udev;
> + wait_queue_head_t ul_wq;
> +
> + /* ul channel lock to synchronize multiple writes */

I asked you to move these comments to Kdoc in previous iteration.

> + struct mutex write_lock;
> +
> + wait_queue_head_t dl_wq;
> +
> + /* dl channel lock to synchronize multiple reads */
> + struct mutex read_lock;
> +
> + /*
> + * protects pending list in bh context, channel release, read and
> + * poll
> + */
> + spinlock_t dl_pending_lock;
> +
> + struct list_head dl_pending;
> + struct uci_buf *cur_buf;
> + size_t dl_size;
> + struct kref ref_count;

I'm now thinking that instead of having two reference counts for uci_chan and
uci_dev, why can't you club them together and just use uci_dev's refcount to
handle the channel management also.

For instance in uci_open, you are incrementing the refcount for uci_dev before
starting the channel and then doing the same for uci_chan in
mhi_uci_dev_start_chan(). So why can't you just use a single refcount once the
mhi_uci_dev_start_chan() succeeds? The UCI device is useless without a channel,
isn't it?

> +};
> +
> +/**
> + * struct uci_buf - UCI buffer
> + * @data: data buffer
> + * @len: length of data buffer
> + * @node: list node of the UCI buffer
> + */
> +struct uci_buf {
> + void *data;
> + size_t len;
> + struct list_head node;
> +};
> +
> +/**
> + * struct uci_dev - MHI UCI device
> + * @minor: UCI device node minor number
> + * @mhi_dev: associated mhi device object
> + * @uchan: UCI uplink and downlink channel object
> + * @mtu: max TRE buffer length
> + * @enabled: Flag to track the state of the UCI device
> + * @lock: mutex lock to manage uchan object
> + * @ref_count: uci_dev reference count
> + */
> +struct uci_dev {
> + unsigned int minor;
> + struct mhi_device *mhi_dev;
> + struct uci_chan *uchan;
> + size_t mtu;
> + bool enabled;
> +
> + /* synchronize open, release and driver remove */
> + struct mutex lock;
> + struct kref ref_count;
> +};
> +
> +static void mhi_uci_dev_chan_release(struct kref *ref)
> +{
> + struct uci_buf *buf_itr, *tmp;
> + struct uci_chan *uchan =
> + container_of(ref, struct uci_chan, ref_count);
> +
> + if (uchan->udev->enabled)
> + mhi_unprepare_from_transfer(uchan->udev->mhi_dev);
> +
> + spin_lock_bh(&uchan->dl_pending_lock);
> + list_for_each_entry_safe(buf_itr, tmp, &uchan->dl_pending, node) {
> + list_del(&buf_itr->node);
> + kfree(buf_itr->data);
> + }
> + spin_unlock_bh(&uchan->dl_pending_lock);
> +
> + wake_up(&uchan->ul_wq);
> + wake_up(&uchan->dl_wq);
> +
> + mutex_lock(&uchan->read_lock);
> + if (uchan->cur_buf)
> + kfree(uchan->cur_buf->data);
> +
> + uchan->cur_buf = NULL;
> + mutex_unlock(&uchan->read_lock);
> +
> + mutex_destroy(&uchan->write_lock);
> + mutex_destroy(&uchan->read_lock);
> +
> + uchan->udev->uchan = NULL;
> + kfree(uchan);
> +}
> +
> +static int mhi_queue_inbound(struct uci_dev *udev)
> +{
> + struct mhi_device *mhi_dev = udev->mhi_dev;
> + struct device *dev = &mhi_dev->dev;
> + int nr_trbs, i, ret = -EIO;

s/nr_trbs/nr_desc

> + size_t dl_buf_size;
> + void *buf;
> + struct uci_buf *ubuf;
> +
> + /* dont queue if dl channel is not supported */
> + if (!udev->mhi_dev->dl_chan)
> + return 0;

Not returning an error?

> +
> + nr_trbs = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);
> +
> + for (i = 0; i < nr_trbs; i++) {
> + buf = kmalloc(udev->mtu, GFP_KERNEL);
> + if (!buf)
> + return -ENOMEM;
> +
> + dl_buf_size = udev->mtu - sizeof(*ubuf);
> +
> + /* save uci_buf info at the end of buf */
> + ubuf = buf + dl_buf_size;
> + ubuf->data = buf;
> +
> + dev_dbg(dev, "Allocated buf %d of %d size %zu\n", i, nr_trbs,
> + dl_buf_size);
> +
> + ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, buf, dl_buf_size,
> + MHI_EOT);
> + if (ret) {
> + kfree(buf);
> + dev_err(dev, "Failed to queue buffer %d\n", i);
> + return ret;
> + }
> + }
> +
> + return ret;
> +}
> +
> +static int mhi_uci_dev_start_chan(struct uci_dev *udev)
> +{
> + int ret = 0;
> + struct uci_chan *uchan;
> +
> + mutex_lock(&udev->lock);
> + if (!udev->uchan || !kref_get_unless_zero(&udev->uchan->ref_count)) {
> + uchan = kzalloc(sizeof(*uchan), GFP_KERNEL);
> + if (!uchan) {
> + ret = -ENOMEM;
> + goto error_chan_start;
> + }
> +
> + udev->uchan = uchan;
> + uchan->udev = udev;
> + init_waitqueue_head(&uchan->ul_wq);
> + init_waitqueue_head(&uchan->dl_wq);
> + mutex_init(&uchan->write_lock);
> + mutex_init(&uchan->read_lock);
> + spin_lock_init(&uchan->dl_pending_lock);
> + INIT_LIST_HEAD(&uchan->dl_pending);
> +
> + ret = mhi_prepare_for_transfer(udev->mhi_dev);
> + if (ret) {
> + dev_err(&udev->mhi_dev->dev, "Error starting transfer channels\n");
> + goto error_chan_cleanup;
> + }
> +
> + ret = mhi_queue_inbound(udev);
> + if (ret)
> + goto error_chan_cleanup;
> +
> + kref_init(&uchan->ref_count);
> + }
> +
> + mutex_unlock(&udev->lock);
> +
> + return 0;
> +
> +error_chan_cleanup:
> + mhi_uci_dev_chan_release(&uchan->ref_count);
> +error_chan_start:
> + mutex_unlock(&udev->lock);
> + return ret;
> +}
> +
> +static void mhi_uci_dev_release(struct kref *ref)
> +{
> + struct uci_dev *udev =
> + container_of(ref, struct uci_dev, ref_count);
> +
> + mutex_destroy(&udev->lock);
> +
> + kfree(udev);
> +}
> +
> +static int mhi_uci_open(struct inode *inode, struct file *filp)
> +{
> + unsigned int minor = iminor(inode);
> + struct uci_dev *udev = NULL;
> + int ret;
> +
> + mutex_lock(&uci_drv_mutex);
> + udev = idr_find(&uci_idr, minor);
> + if (!udev) {
> + pr_debug("uci dev: minor %d not found\n", minor);
> + mutex_unlock(&uci_drv_mutex);
> + return -ENODEV;
> + }
> +
> + kref_get(&udev->ref_count);
> + mutex_unlock(&uci_drv_mutex);
> +
> + ret = mhi_uci_dev_start_chan(udev);
> + if (ret) {
> + kref_put(&udev->ref_count, mhi_uci_dev_release);
> + return ret;
> + }
> +
> + filp->private_data = udev;
> +
> + return 0;
> +}
> +
> +static int mhi_uci_release(struct inode *inode, struct file *file)
> +{
> + struct uci_dev *udev = file->private_data;
> +
> + mutex_lock(&udev->lock);
> + kref_put(&udev->uchan->ref_count, mhi_uci_dev_chan_release);
> + mutex_unlock(&udev->lock);
> +
> + kref_put(&udev->ref_count, mhi_uci_dev_release);
> +
> + return 0;
> +}
> +
> +static __poll_t mhi_uci_poll(struct file *file, poll_table *wait)
> +{
> + struct uci_dev *udev = file->private_data;
> + struct mhi_device *mhi_dev = udev->mhi_dev;
> + struct device *dev = &mhi_dev->dev;
> + struct uci_chan *uchan = udev->uchan;
> + __poll_t mask = 0;
> +
> + poll_wait(file, &udev->uchan->ul_wq, wait);
> + poll_wait(file, &udev->uchan->dl_wq, wait);
> +
> + if (!udev->enabled) {
> + mask = EPOLLERR;
> + goto done;
> + }
> +
> + spin_lock_bh(&uchan->dl_pending_lock);
> + if (!list_empty(&uchan->dl_pending) || uchan->cur_buf) {
> + dev_dbg(dev, "Client can read from node\n");

Since you're printing the mask, no need of the debug statement here.

> + mask |= EPOLLIN | EPOLLRDNORM;
> + }
> + spin_unlock_bh(&uchan->dl_pending_lock);
> +
> + if (mhi_get_free_desc_count(mhi_dev, DMA_TO_DEVICE) > 0) {
> + dev_dbg(dev, "Client can write to node\n");

Same as above.

> + mask |= EPOLLOUT | EPOLLWRNORM;
> + }
> +
> + dev_dbg(dev, "Client attempted to poll, returning mask 0x%x\n", mask);
> +
> +done:
> + return mask;
> +}
> +
> +static ssize_t mhi_uci_write(struct file *file,
> + const char __user *buf,
> + size_t count,
> + loff_t *offp)
> +{
> + struct uci_dev *udev = file->private_data;
> + struct mhi_device *mhi_dev = udev->mhi_dev;
> + struct device *dev = &mhi_dev->dev;
> + struct uci_chan *uchan = udev->uchan;
> + size_t bytes_xfered = 0;
> + int ret, nr_avail = 0;

s/nr_avail/nr_desc

> +
> + /* if ul channel is not supported return error */
> + if (!buf || !count || !mhi_dev->ul_chan)

Shouldn't we return ENOTSUPP for !mhi_dev->dl_chan?

> + return -EINVAL;
> +
> + dev_dbg(dev, "%s: to xfer: %zu bytes\n", __func__, count);
> +
> + if (mutex_lock_interruptible(&uchan->write_lock))
> + return -EINTR;
> +
> + while (count) {
> + size_t xfer_size;
> + void *kbuf;
> + enum mhi_flags flags;
> +
> + /* wait for free descriptors */
> + ret = wait_event_interruptible(uchan->ul_wq,
> + (!udev->enabled) ||
> + (nr_avail = mhi_get_free_desc_count(mhi_dev,
> + DMA_TO_DEVICE)) > 0);
> +
> + if (ret == -ERESTARTSYS) {
> + dev_dbg(dev, "Interrupted by a signal in %s, exiting\n",
> + __func__);
> + goto err_mtx_unlock;
> + }
> +
> + if (!udev->enabled) {
> + ret = -ENODEV;
> + goto err_mtx_unlock;
> + }
> +
> + xfer_size = min_t(size_t, count, udev->mtu);
> + kbuf = kmalloc(xfer_size, GFP_KERNEL);
> + if (!kbuf) {
> + ret = -ENOMEM;
> + goto err_mtx_unlock;
> + }
> +
> + ret = copy_from_user(kbuf, buf, xfer_size);
> + if (ret) {
> + kfree(kbuf);
> + ret = -EFAULT;
> + goto err_mtx_unlock;
> + }
> +
> + /* if ring is full after this force EOT */
> + if (nr_avail > 1 && (count - xfer_size))
> + flags = MHI_CHAIN;
> + else
> + flags = MHI_EOT;
> +
> + ret = mhi_queue_buf(mhi_dev, DMA_TO_DEVICE, kbuf, xfer_size,
> + flags);
> + if (ret) {
> + kfree(kbuf);
> + goto err_mtx_unlock;
> + }
> +
> + bytes_xfered += xfer_size;
> + count -= xfer_size;
> + buf += xfer_size;
> + }
> +
> + mutex_unlock(&uchan->write_lock);
> + dev_dbg(dev, "%s: bytes xferred: %zu\n", __func__, bytes_xfered);
> +
> + return bytes_xfered;
> +
> +err_mtx_unlock:
> + mutex_unlock(&uchan->write_lock);
> +
> + return ret;
> +}
> +
> +static ssize_t mhi_uci_read(struct file *file,
> + char __user *buf,
> + size_t count,
> + loff_t *ppos)
> +{
> + struct uci_dev *udev = file->private_data;
> + struct mhi_device *mhi_dev = udev->mhi_dev;
> + struct uci_chan *uchan = udev->uchan;
> + struct device *dev = &mhi_dev->dev;
> + struct uci_buf *ubuf;
> + size_t rx_buf_size;
> + char *ptr;
> + size_t to_copy;
> + int ret = 0;
> +
> + /* if dl channel is not supported return error */
> + if (!buf || !mhi_dev->dl_chan)
> + return -EINVAL;

Shouldn't we return ENOTSUPP for !mhi_dev->dl_chan?

> +
> + if (mutex_lock_interruptible(&uchan->read_lock))
> + return -EINTR;
> +
> + spin_lock_bh(&uchan->dl_pending_lock);
> + /* No data available to read, wait */
> + if (!uchan->cur_buf && list_empty(&uchan->dl_pending)) {
> + dev_dbg(dev, "No data available to read, waiting\n");
> +
> + spin_unlock_bh(&uchan->dl_pending_lock);
> + ret = wait_event_interruptible(uchan->dl_wq,
> + (!udev->enabled ||
> + !list_empty(&uchan->dl_pending)));
> +
> + if (ret == -ERESTARTSYS) {
> + dev_dbg(dev, "Interrupted by a signal in %s, exiting\n",
> + __func__);
> + goto err_mtx_unlock;
> + }
> +
> + if (!udev->enabled) {
> + ret = -ENODEV;
> + goto err_mtx_unlock;
> + }
> + spin_lock_bh(&uchan->dl_pending_lock);
> + }
> +
> + /* new read, get the next descriptor from the list */
> + if (!uchan->cur_buf) {
> + ubuf = list_first_entry_or_null(&uchan->dl_pending,
> + struct uci_buf, node);
> + if (!ubuf) {
> + ret = -EIO;
> + goto err_spin_unlock;
> + }
> +
> + list_del(&ubuf->node);
> + uchan->cur_buf = ubuf;
> + uchan->dl_size = ubuf->len;
> + dev_dbg(dev, "Got pkt of size: %zu\n", uchan->dl_size);
> + }
> + spin_unlock_bh(&uchan->dl_pending_lock);
> +
> + ubuf = uchan->cur_buf;
> +
> + /* Copy the buffer to user space */
> + to_copy = min_t(size_t, count, uchan->dl_size);
> + ptr = ubuf->data + (ubuf->len - uchan->dl_size);
> +
> + ret = copy_to_user(buf, ptr, to_copy);
> + if (ret) {
> + ret = -EFAULT;
> + goto err_mtx_unlock;
> + }
> +
> + dev_dbg(dev, "Copied %zu of %zu bytes\n", to_copy, uchan->dl_size);
> + uchan->dl_size -= to_copy;
> +
> + /* we finished with this buffer, queue it back to hardware */
> + if (!uchan->dl_size) {
> + uchan->cur_buf = NULL;
> +
> + rx_buf_size = udev->mtu - sizeof(*ubuf);
> + ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, ubuf->data,
> + rx_buf_size, MHI_EOT);
> + if (ret) {
> + dev_err(dev, "Failed to recycle element: %d\n", ret);
> + kfree(ubuf->data);
> + goto err_mtx_unlock;
> + }
> + }
> + mutex_unlock(&uchan->read_lock);
> +
> + dev_dbg(dev, "%s: Returning %zu bytes\n", __func__, to_copy);
> +
> + return to_copy;
> +
> +err_spin_unlock:
> + spin_unlock_bh(&uchan->dl_pending_lock);
> +err_mtx_unlock:
> + mutex_unlock(&uchan->read_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 *udev = dev_get_drvdata(&mhi_dev->dev);
> + struct uci_chan *uchan = udev->uchan;
> + struct device *dev = &mhi_dev->dev;
> +
> + dev_dbg(dev, "status: %d xfer_len: %zu\n",
> + mhi_result->transaction_status, mhi_result->bytes_xferd);

How this print is going to be useful alone? Atleast you should print the
function name.

> +
> + kfree(mhi_result->buf_addr);
> +
> + if (!mhi_result->transaction_status)
> + wake_up(&uchan->ul_wq);
> +}
> +
> +static void mhi_dl_xfer_cb(struct mhi_device *mhi_dev,
> + struct mhi_result *mhi_result)
> +{
> + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev);
> + struct uci_chan *uchan = udev->uchan;
> + struct device *dev = &mhi_dev->dev;
> + struct uci_buf *ubuf;
> + size_t dl_buf_size = udev->mtu - sizeof(*ubuf);
> +
> + dev_dbg(dev, "status: %d receive_len: %zu\n",
> + mhi_result->transaction_status, mhi_result->bytes_xferd);

Same as above.

> +
> + if (mhi_result->transaction_status &&
> + mhi_result->transaction_status != -EOVERFLOW) {
> + kfree(mhi_result->buf_addr);
> + return;
> + }
> +
> + ubuf = mhi_result->buf_addr + dl_buf_size;
> + ubuf->data = mhi_result->buf_addr;
> + ubuf->len = mhi_result->bytes_xferd;
> + spin_lock_bh(&uchan->dl_pending_lock);
> + list_add_tail(&ubuf->node, &uchan->dl_pending);
> + spin_unlock_bh(&uchan->dl_pending_lock);
> +
> + wake_up(&uchan->dl_wq);
> +}
> +
> +static int mhi_uci_probe(struct mhi_device *mhi_dev,
> + const struct mhi_device_id *id)
> +{
> + struct uci_dev *udev;
> + struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
> + struct device *dev;
> + int index;
> +
> + udev = kzalloc(sizeof(*udev), GFP_KERNEL);
> + if (!udev)
> + return -ENOMEM;
> +
> + kref_init(&udev->ref_count);
> + mutex_init(&udev->lock);
> + udev->mhi_dev = mhi_dev;
> +
> + mutex_lock(&uci_drv_mutex);
> + index = idr_alloc(&uci_idr, udev, 0, MAX_UCI_MINORS, GFP_KERNEL);
> + mutex_unlock(&uci_drv_mutex);
> + if (index < 0) {
> + kfree(udev);
> + return index;
> + }
> +
> + udev->minor = index;
> +
> + udev->mtu = min_t(size_t, id->driver_data, MHI_MAX_MTU);
> + dev_set_drvdata(&mhi_dev->dev, udev);
> + udev->enabled = true;
> +
> + /* create device file node /dev/mhi_<cntrl_dev_name>_<mhi_dev_name> */
> + dev = device_create(uci_dev_class, &mhi_dev->dev,
> + MKDEV(uci_dev_major, index), udev,
> + DEVICE_NAME "_%s_%s",
> + dev_name(mhi_cntrl->cntrl_dev), mhi_dev->name);
> + if (IS_ERR(dev)) {
> + mutex_lock(&uci_drv_mutex);
> + idr_remove(&uci_idr, udev->minor);
> + mutex_unlock(&uci_drv_mutex);
> + dev_set_drvdata(&mhi_dev->dev, NULL);
> + kfree(udev);
> + return PTR_ERR(dev);
> + }
> +
> + dev_dbg(&mhi_dev->dev, "probed uci dev: %s\n", id->chan);
> +
> + return 0;
> +};
> +
> +static void mhi_uci_remove(struct mhi_device *mhi_dev)
> +{
> + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev);
> +
> + /* disable the node */
> + mutex_lock(&udev->lock);
> + udev->enabled = false;
> +
> + /* delete the node to prevent new opens */
> + device_destroy(uci_dev_class, MKDEV(uci_dev_major, udev->minor));
> +
> + /* return error for any blocked read or write */
> + if (udev->uchan) {
> + wake_up(&udev->uchan->ul_wq);
> + wake_up(&udev->uchan->dl_wq);
> + }
> + mutex_unlock(&udev->lock);
> +
> + mutex_lock(&uci_drv_mutex);
> + idr_remove(&uci_idr, udev->minor);
> + kref_put(&udev->ref_count, mhi_uci_dev_release);
> + mutex_unlock(&uci_drv_mutex);
> +}
> +
> +/* .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 __init mhi_uci_init(void)
> +{
> + int ret;
> +
> + ret = register_chrdev(0, MHI_UCI_DRIVER_NAME, &mhidev_fops);
> + if (ret < 0)
> + return ret;
> +
> + uci_dev_major = ret;
> + uci_dev_class = class_create(THIS_MODULE, MHI_UCI_DRIVER_NAME);
> + if (IS_ERR(uci_dev_class)) {
> + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME);
> + return PTR_ERR(uci_dev_class);
> + }
> +
> + ret = mhi_driver_register(&mhi_uci_driver);
> + if (ret) {
> + class_destroy(uci_dev_class);
> + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME);
> + }
> +
> + return ret;
> +}
> +
> +static void __exit mhi_uci_exit(void)
> +{
> + mhi_driver_unregister(&mhi_uci_driver);
> + class_destroy(uci_dev_class);
> + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME);
> + idr_destroy(&uci_idr);
> +}
> +
> +module_init(mhi_uci_init);
> +module_exit(mhi_uci_exit);
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("MHI UCI Driver");
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>