Re: [PATCH v4 4/4] bus: mhi: clients: Add userspace client interface driver

Greg KH
2020-07-29T06:18:06Z

On Tue, Jul 28, 2020 at 08:46:35PM -0700, Hemant Kumar wrote:
> This MHI client driver allows userspace clients to transfer
> raw 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 channel.
>
> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
> ---
> drivers/bus/mhi/Kconfig | 6 +
> drivers/bus/mhi/Makefile | 1 +
> drivers/bus/mhi/clients/Kconfig | 15 +
> drivers/bus/mhi/clients/Makefile | 3 +
> drivers/bus/mhi/clients/uci.c | 690 +++++++++++++++++++++++++++++++++++++++
> 5 files changed, 715 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..927c392 100644
> --- a/drivers/bus/mhi/Kconfig
> +++ b/drivers/bus/mhi/Kconfig
> @@ -20,3 +20,9 @@ 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.
> +
> +if MHI_BUS
> +
> +source "drivers/bus/mhi/clients/Kconfig"
> +
> +endif
> 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..37aaf51
> --- /dev/null
> +++ b/drivers/bus/mhi/clients/Kconfig
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +
> +menu "MHI clients support"
> +
> +config MHI_UCI
> + tristate "MHI UCI"
> + depends on MHI_BUS
> + help
> + MHI based userspace client interface 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.
> +
> +endmenu
> diff --git a/drivers/bus/mhi/clients/Makefile b/drivers/bus/mhi/clients/Makefile
> new file mode 100644
> index 0000000..cd34282
> --- /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..3ddf017
> --- /dev/null
> +++ b/drivers/bus/mhi/clients/uci.c
> @@ -0,0 +1,690 @@
> +// 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_DEVICES (64)
> +
> +/**
> + * struct uci_chan - MHI channel for a uci device
> + * @wq: wait queue for reader/writer
> + * @lock: spin lock
> + * @pending: list of rx buffers userspace is waiting to read
> + * @cur_buf: current buffer userspace is reading
> + * @rx_size: size of the current rx buffer userspace is reading
> + */
> +struct uci_chan {
> + wait_queue_head_t wq;
> +
> + /* protects pending and cur_buf members */
> + spinlock_t lock;
> +
> + struct list_head pending;
> + struct uci_buf *cur_buf;
> + size_t rx_size;
> +};
> +
> +/**
> + * 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 mhi_uci_drv - MHI uci driver
> + * @head: list head of a uci device nodes
> + * @lock: mutex lock
> + * @class: current buffer userspace is reading
> + * @major: major number for uci driver
> + * @devt: dev_t object to hold major and minor info
> + */
> +struct mhi_uci_drv {
> + struct list_head head;
> +
> + /* protects mhi_uci_drv struct members */
> + struct mutex lock;
> +
> + struct class *class;
> + int major;
> + dev_t devt;
> +};

So this is just a single static structure for some "global" variables
for the driver? Why make it a structure at all?

And why have a local list of all devices, doesn't the driver core give
that to you already? You shouldn't need that if you are doing things
properly...

> +
> +/**
> + * struct uci_dev - MHI uci device
> + * @node: uci device node
> + * @devt: dev_t object to hold major and minor info
> + * @dev: uci device object
> + * @mhi_dev: associated mhi device object
> + * @chan: MHI channel name
> + * @lock: mutex lock
> + * @ul_chan: uplink uci channel object
> + * @dl_chan: downlink uci channel object
> + * @mtu: max tx buffer length
> + * @actual_mtu: maximum size of incoming buffer
> + * @ref_count: uci_dev reference count
> + * @enabled: uci device node accessibility
> + */
> +struct uci_dev {
> + struct list_head node;
> + dev_t devt;
> + struct device *dev;

This points to what? Why isn't this structure a 'struct device' and
then just point to the parent passed to it?

> + struct mhi_device *mhi_dev;
> + const char *chan;
> +
> + /* protects uci_dev struct members */
> + struct mutex lock;
> +
> + struct uci_chan ul_chan;
> + struct uci_chan dl_chan;
> + size_t mtu;
> + size_t actual_mtu;
> + int ref_count;

Huh? What is this used for? We do have proper refcount structures/apis
if you really want that, do not roll your own.

> + bool enabled;
> +};
> +
> +static DECLARE_BITMAP(uci_minors, MAX_UCI_DEVICES);

Why is this needed? Why not use an idr/ida structure instead?

> +static struct mhi_uci_drv uci_drv;

Here's that single device list :(

> +
> +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;
> + size_t mtu = uci_dev->mtu;
> + size_t actual_mtu = uci_dev->actual_mtu;
> + int nr_trbs, i, ret = -EIO;
> + void *buf;
> + struct uci_buf *uci_buf;
> +
> + nr_trbs = mhi_get_no_free_descriptors(mhi_dev, DMA_FROM_DEVICE);
> +
> + 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->lock);
> + 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;
> +
> + spin_lock_bh(&uci_chan->lock);
> + 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;
> + spin_unlock_bh(&uci_chan->lock);
> +
> + if (!uci_dev->enabled) {
> + mutex_unlock(&uci_dev->lock);
> + mutex_destroy(&uci_dev->lock);
> + clear_bit(MINOR(uci_dev->devt), uci_minors);
> + kfree(uci_dev);
> + return 0;
> + }
> + }
> +
> + mutex_unlock(&uci_dev->lock);
> +
> + 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);
> +
> + if (!uci_dev->enabled) {
> + mask = EPOLLERR;
> + } else {
> + uci_chan = &uci_dev->dl_chan;
> + spin_lock_bh(&uci_chan->lock);
> + 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);
> + }
> +
> + 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;
> + }
> +
> + 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 = 0;
> +
> + if (!buf || !count)
> + return -EINVAL;
> +
> + /* confirm channel is active */
> + mutex_lock(&uci_dev->lock);
> + if (!uci_dev->enabled) {
> + ret = -ENODEV;
> + goto err_mtx_unlock;
> + }
> +
> + dev_dbg(dev, "%s: to xfer: %lu bytes\n", __func__, count);
> +
> + while (count) {
> + size_t xfer_size;
> + void *kbuf;
> + enum mhi_flags flags;
> +
> + mutex_unlock(&uci_dev->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);

Can this ever timeout?

> +
> + mutex_lock(&uci_dev->lock);
> + if (ret == -ERESTARTSYS) {
> + dev_dbg(dev, "Exit signal caught for node\n");
> + goto err_mtx_unlock;
> + }
> +
> + if (!uci_dev->enabled) {
> + ret = -ENODEV;
> + goto err_mtx_unlock;
> + }
> +
> + xfer_size = min_t(size_t, count, uci_dev->mtu);
> + kbuf = kmalloc(xfer_size, GFP_KERNEL);
> + if (!kbuf) {
> + ret = -ENOMEM;
> + goto err_mtx_unlock;
> + }
> +
> + ret = copy_from_user(kbuf, buf, xfer_size);
> + if (unlikely(ret)) {

Only ever use likely/unlikely if you can test the difference. Can you
here? Otherwise the compiler/cpu will almost always do it better for
you.

> + kfree(kbuf);
> + goto err_mtx_unlock;

Wrong error code sent to userspace :(

> + }
> +
> + /* 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 = -ENODEV;
> +
> + if (ret) {
> + kfree(kbuf);
> + goto err_mtx_unlock;
> + }
> +
> + bytes_xfered += xfer_size;
> + count -= xfer_size;
> + buf += xfer_size;
> + }
> +
> + mutex_unlock(&uci_dev->lock);
> + dev_dbg(dev, "%s: bytes xferred: %lu\n", __func__, bytes_xfered);
> +
> + return bytes_xfered;
> +
> +err_mtx_unlock:
> + mutex_unlock(&uci_dev->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;
> +
> + mutex_lock(&uci_dev->lock);
> + /* confirm channel is active */
> + if (!uci_dev->enabled) {
> + ret = -ENODEV;
> + goto err_mtx_unlock;
> + }
> +
> + spin_lock_bh(&uci_chan->lock);
> + /* 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->lock);
> + ret = wait_event_interruptible(uci_chan->wq,
> + (!uci_dev->enabled ||
> + !list_empty(&uci_chan->pending)));

any chance to timeout?

> +
> + mutex_lock(&uci_dev->lock);
> + if (ret == -ERESTARTSYS) {
> + dev_dbg(dev, "Exit signal caught for node\n");
> + goto err_mtx_unlock;
> + }
> +
> + if (!uci_dev->enabled) {
> + ret = -ENODEV;
> + goto err_mtx_unlock;
> + }
> + spin_lock_bh(&uci_chan->lock);
> + }
> +
> + /* 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)) {

Again, prove it otherwise do not use these markings.

> + ret = -EIO;
> + goto err_spin_unlock;
> + }
> +
> + 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_mtx_unlock;

You forgot to set the proper error value here :(

> +
> + 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 = -ENODEV;
> +
> + if (ret) {
> + dev_err(dev, "Failed to recycle element\n");
> + kfree(uci_buf->data);
> + goto err_spin_unlock;
> + }
> + }
> + spin_unlock_bh(&uci_chan->lock);
> + mutex_unlock(&uci_dev->lock);
> +
> + dev_dbg(dev, "%s: Returning %lu bytes\n", __func__, to_copy);
> +
> + return to_copy;
> +
> +err_spin_unlock:
> + spin_unlock_bh(&uci_chan->lock);
> +err_mtx_unlock:
> + mutex_unlock(&uci_dev->lock);
> + 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(&uci_drv.lock);
> + list_for_each_entry(tmp_dev, &uci_drv.head, node) {
> + if (tmp_dev->devt == inode->i_rdev) {
> + uci_dev = tmp_dev;

Really? There's no other way to look this up?

> + break;
> + }
> + }
> + mutex_unlock(&uci_drv.lock);
> +
> + /* could not find a minor node */
> + if (!uci_dev) {
> + pr_err("Error finding uci device\n");
> + ret = -ENODEV;
> + goto error_exit;
> + }
> +
> + mhi_dev = uci_dev->mhi_dev;
> + dev = &mhi_dev->dev;
> +
> + mutex_lock(&uci_dev->lock);
> + 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->lock);
> +
> + return 0;
> +
> +error_rx_queue:
> + uci_dev->ref_count--;
> + 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->lock);
> +
> +error_exit:
> + 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;
> + 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_bh(&uci_chan->lock);
> + 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_bh(&uci_chan->lock);
> +
> + 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->lock);
> + uci_dev->mhi_dev = mhi_dev;
> +
> + mutex_lock(&uci_dev->lock);
> +
> + mutex_lock(&uci_drv.lock);
> + minor = find_first_zero_bit(uci_minors, MAX_UCI_DEVICES);
> + if (minor >= MAX_UCI_DEVICES) {
> + mutex_unlock(&uci_drv.lock);
> + mutex_unlock(&uci_dev->lock);
> + kfree(uci_dev);
> + return -ENOSPC;
> + }
> +
> + /* create device file node /dev/mhi_<cntrl_dev_name>_<mhi_dev_name> */
> + uci_dev->devt = MKDEV(uci_drv.major, minor);
> + uci_dev->dev = device_create(uci_drv.class, &mhi_dev->dev,
> + uci_dev->devt, uci_dev,
> + DEVICE_NAME "_%s_%s",
> + dev_name(mhi_cntrl->cntrl_dev),
> + mhi_dev->name);

No error checking if device_create() worked or not?

:(

> + 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, &uci_drv.head);
> + mutex_unlock(&uci_drv.lock);
> +
> + mutex_unlock(&uci_dev->lock);
> +
> + dev_info(dev, "successfully probed\n");
> +
> + 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, "removing\n");

Debugging stuff like this can now be removed, ftrace is your friend..

> +
> + mutex_lock(&uci_drv.lock);
> + mutex_lock(&uci_dev->lock);
> +
> + /* disable the node */
> + uci_dev->enabled = false;
> +
> + wake_up(&uci_dev->dl_chan.wq);
> + wake_up(&uci_dev->ul_chan.wq);
> +
> + /* delete the node to prevent new opens */
> + device_destroy(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->lock);
> + mutex_destroy(&uci_dev->lock);
> + clear_bit(MINOR(uci_dev->devt), uci_minors);
> + dev_set_drvdata(&mhi_dev->dev, NULL);
> + kfree(uci_dev);
> + mutex_unlock(&uci_drv.lock);
> + return;
> + }
> +
> + mutex_unlock(&uci_dev->lock);
> + mutex_unlock(&uci_drv.lock);
> +
> + dev_dbg(dev, "removed\n");
> +}
> +
> +/* .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;

A whole major for this thing? How many minor devices are you going to
have?

thanks,

greg k-h