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 <hema...@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