Re: [PATCH v2 1/8] drivers: most: add usb adapter driver

[Dan Carpenter <dan.carpenter@oracle.com>]

On Thu, May 14, 2020 at 11:52:49AM +0200, Christian Gromm wrote:
> This patch adds the usb driver source file most_usb.c and
> modifies the Makefile and Kconfig accordingly.
> 
> Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
> ---
> v2:
> Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 	- don't remove usb driver from staging area
> 	- don't touch staging/most/Kconfig
> 	- remove subdirectory for USB driver and put source file into
> 	  drivers/most
> 
>  drivers/most/Kconfig    |   12 +
>  drivers/most/Makefile   |    2 +
>  drivers/most/most_usb.c | 1262 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 1276 insertions(+)
>  create mode 100644 drivers/most/most_usb.c
> 
> diff --git a/drivers/most/Kconfig b/drivers/most/Kconfig
> index 58d7999..8650683 100644
> --- a/drivers/most/Kconfig
> +++ b/drivers/most/Kconfig
> @@ -13,3 +13,15 @@ menuconfig MOST
>  	  module will be called most_core.
>  
>  	  If in doubt, say N here.
> +
> +if MOST
> +config MOST_USB
> +	tristate "USB"
> +	depends on USB && NET
> +	help
> +	  Say Y here if you want to connect via USB to network tranceiver.
> +	  This device driver depends on the networking AIM.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called most_usb.
> +endif
> diff --git a/drivers/most/Makefile b/drivers/most/Makefile
> index e810cd3..97ffc06 100644
> --- a/drivers/most/Makefile
> +++ b/drivers/most/Makefile
> @@ -2,3 +2,5 @@
>  obj-$(CONFIG_MOST) += most_core.o
>  most_core-y :=	core.o \
>  		configfs.o
> +
> +obj-$(CONFIG_MOST_USB) += most_usb.o
> diff --git a/drivers/most/most_usb.c b/drivers/most/most_usb.c
> new file mode 100644
> index 0000000..daa5e4b
> --- /dev/null
> +++ b/drivers/most/most_usb.c
> @@ -0,0 +1,1262 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * usb.c - Hardware dependent module for USB
> + *
> + * Copyright (C) 2013-2015 Microchip Technology Germany II GmbH & Co. KG
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +#include <linux/module.h>
> +#include <linux/fs.h>
> +#include <linux/usb.h>
> +#include <linux/slab.h>
> +#include <linux/init.h>
> +#include <linux/cdev.h>
> +#include <linux/device.h>
> +#include <linux/list.h>
> +#include <linux/completion.h>
> +#include <linux/mutex.h>
> +#include <linux/spinlock.h>
> +#include <linux/interrupt.h>
> +#include <linux/workqueue.h>
> +#include <linux/sysfs.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/etherdevice.h>
> +#include <linux/uaccess.h>
> +#include <linux/most.h>
> +
> +#define USB_MTU			512
> +#define NO_ISOCHRONOUS_URB	0
> +#define AV_PACKETS_PER_XACT	2
> +#define BUF_CHAIN_SIZE		0xFFFF
> +#define MAX_NUM_ENDPOINTS	30
> +#define MAX_SUFFIX_LEN		10
> +#define MAX_STRING_LEN		80
> +#define MAX_BUF_SIZE		0xFFFF
> +
> +#define USB_VENDOR_ID_SMSC	0x0424  /* VID: SMSC */
> +#define USB_DEV_ID_BRDG		0xC001  /* PID: USB Bridge */
> +#define USB_DEV_ID_OS81118	0xCF18  /* PID: USB OS81118 */
> +#define USB_DEV_ID_OS81119	0xCF19  /* PID: USB OS81119 */
> +#define USB_DEV_ID_OS81210	0xCF30  /* PID: USB OS81210 */
> +/* DRCI Addresses */
> +#define DRCI_REG_NI_STATE	0x0100
> +#define DRCI_REG_PACKET_BW	0x0101
> +#define DRCI_REG_NODE_ADDR	0x0102
> +#define DRCI_REG_NODE_POS	0x0103
> +#define DRCI_REG_MEP_FILTER	0x0140
> +#define DRCI_REG_HASH_TBL0	0x0141
> +#define DRCI_REG_HASH_TBL1	0x0142
> +#define DRCI_REG_HASH_TBL2	0x0143
> +#define DRCI_REG_HASH_TBL3	0x0144
> +#define DRCI_REG_HW_ADDR_HI	0x0145
> +#define DRCI_REG_HW_ADDR_MI	0x0146
> +#define DRCI_REG_HW_ADDR_LO	0x0147
> +#define DRCI_REG_BASE		0x1100
> +#define DRCI_COMMAND		0x02
> +#define DRCI_READ_REQ		0xA0
> +#define DRCI_WRITE_REQ		0xA1
> +
> +/**
> + * struct most_dci_obj - Direct Communication Interface
> + * @kobj:position in sysfs
> + * @usb_device: pointer to the usb device
> + * @reg_addr: register address for arbitrary DCI access
> + */
> +struct most_dci_obj {
> +	struct device dev;
> +	struct usb_device *usb_device;
> +	u16 reg_addr;
> +};
> +
> +#define to_dci_obj(p) container_of(p, struct most_dci_obj, dev)
> +
> +struct most_dev;
> +
> +struct clear_hold_work {
> +	struct work_struct ws;
> +	struct most_dev *mdev;
> +	unsigned int channel;
> +	int pipe;
> +};
> +
> +#define to_clear_hold_work(w) container_of(w, struct clear_hold_work, ws)
> +
> +/**
> + * struct most_dev - holds all usb interface specific stuff
> + * @usb_device: pointer to usb device
> + * @iface: hardware interface
> + * @cap: channel capabilities
> + * @conf: channel configuration
> + * @dci: direct communication interface of hardware
> + * @ep_address: endpoint address table
> + * @description: device description
> + * @suffix: suffix for channel name
> + * @channel_lock: synchronize channel access
> + * @padding_active: indicates channel uses padding
> + * @is_channel_healthy: health status table of each channel
> + * @busy_urbs: list of anchored items
> + * @io_mutex: synchronize I/O with disconnect
> + * @link_stat_timer: timer for link status reports
> + * @poll_work_obj: work for polling link status
> + */
> +struct most_dev {
> +	struct device dev;
> +	struct usb_device *usb_device;
> +	struct most_interface iface;
> +	struct most_channel_capability *cap;
> +	struct most_channel_config *conf;
> +	struct most_dci_obj *dci;
> +	u8 *ep_address;
> +	char description[MAX_STRING_LEN];
> +	char suffix[MAX_NUM_ENDPOINTS][MAX_SUFFIX_LEN];
> +	spinlock_t channel_lock[MAX_NUM_ENDPOINTS]; /* sync channel access */
> +	bool padding_active[MAX_NUM_ENDPOINTS];
> +	bool is_channel_healthy[MAX_NUM_ENDPOINTS];
> +	struct clear_hold_work clear_work[MAX_NUM_ENDPOINTS];
> +	struct usb_anchor *busy_urbs;
> +	struct mutex io_mutex;
> +	struct timer_list link_stat_timer;
> +	struct work_struct poll_work_obj;
> +	void (*on_netinfo)(struct most_interface *most_iface,
> +			   unsigned char link_state, unsigned char *addrs);
> +};
> +
> +#define to_mdev(d) container_of(d, struct most_dev, iface)
> +#define to_mdev_from_dev(d) container_of(d, struct most_dev, dev)
> +#define to_mdev_from_work(w) container_of(w, struct most_dev, poll_work_obj)
> +
> +static void wq_clear_halt(struct work_struct *wq_obj);
> +static void wq_netinfo(struct work_struct *wq_obj);
> +
> +/**
> + * drci_rd_reg - read a DCI register
> + * @dev: usb device
> + * @reg: register address
> + * @buf: buffer to store data
> + *
> + * This is reads data from INIC's direct register communication interface
> + */
> +static inline int drci_rd_reg(struct usb_device *dev, u16 reg, u16 *buf)
> +{
> +	int retval;
> +	__le16 *dma_buf = kzalloc(sizeof(*dma_buf), GFP_KERNEL);

I really hate allocations hidden in the declaration block.  :/

> +	u8 req_type = USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE;
> +
> +	if (!dma_buf)
> +		return -ENOMEM;
> +
> +	retval = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
> +				 DRCI_READ_REQ, req_type,
> +				 0x0000,
> +				 reg, dma_buf, sizeof(*dma_buf), 5 * HZ);
> +	*buf = le16_to_cpu(*dma_buf);
> +	kfree(dma_buf);
> +
> +	return retval;

Why bother returning positive values here when none of the callers use
that?

> +}
> +
> +/**
> + * drci_wr_reg - write a DCI register
> + * @dev: usb device
> + * @reg: register address
> + * @data: data to write
> + *
> + * This is writes data to INIC's direct register communication interface
> + */
> +static inline int drci_wr_reg(struct usb_device *dev, u16 reg, u16 data)
> +{
> +	return usb_control_msg(dev,
> +			       usb_sndctrlpipe(dev, 0),
> +			       DRCI_WRITE_REQ,
> +			       USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
> +			       data,
> +			       reg,
> +			       NULL,
> +			       0,
> +			       5 * HZ);
> +}
> +
> +static inline int start_sync_ep(struct usb_device *usb_dev, u16 ep)
> +{
> +	return drci_wr_reg(usb_dev, DRCI_REG_BASE + DRCI_COMMAND + ep * 16, 1);
> +}
> +
> +/**
> + * get_stream_frame_size - calculate frame size of current configuration
> + * @cfg: channel configuration
> + */
> +static unsigned int get_stream_frame_size(struct most_channel_config *cfg)
> +{
> +	unsigned int frame_size = 0;
> +	unsigned int sub_size = cfg->subbuffer_size;
> +
> +	if (!sub_size) {
> +		pr_warn("Misconfig: Subbuffer size zero.\n");
> +		return frame_size;

I wish this were a "return 0;"

> +	}
> +	switch (cfg->data_type) {
> +	case MOST_CH_ISOC:
> +		frame_size = AV_PACKETS_PER_XACT * sub_size;
> +		break;
> +	case MOST_CH_SYNC:
> +		if (cfg->packets_per_xact == 0) {
> +			pr_warn("Misconfig: Packets per XACT zero\n");
> +			frame_size = 0;
> +		} else if (cfg->packets_per_xact == 0xFF) {
> +			frame_size = (USB_MTU / sub_size) * sub_size;
> +		} else {
> +			frame_size = cfg->packets_per_xact * sub_size;
> +		}
> +		break;
> +	default:
> +		pr_warn("Query frame size of non-streaming channel\n");
> +		break;
> +	}
> +	return frame_size;
> +}
> +
> +/**
> + * hdm_poison_channel - mark buffers of this channel as invalid
> + * @iface: pointer to the interface
> + * @channel: channel ID
> + *
> + * This unlinks all URBs submitted to the HCD,
> + * calls the associated completion function of the core and removes
> + * them from the list.
> + *
> + * Returns 0 on success or error code otherwise.
> + */
> +static int hdm_poison_channel(struct most_interface *iface, int channel)
> +{
> +	struct most_dev *mdev = to_mdev(iface);
> +	unsigned long flags;
> +	spinlock_t *lock; /* temp. lock */
> +
> +	if (channel < 0 || channel >= iface->num_channels) {
> +		dev_warn(&mdev->usb_device->dev, "Channel ID out of range.\n");
> +		return -ECHRNG;
> +	}
> +
> +	lock = mdev->channel_lock + channel;
> +	spin_lock_irqsave(lock, flags);
> +	mdev->is_channel_healthy[channel] = false;
> +	spin_unlock_irqrestore(lock, flags);
> +
> +	cancel_work_sync(&mdev->clear_work[channel].ws);
> +
> +	mutex_lock(&mdev->io_mutex);
> +	usb_kill_anchored_urbs(&mdev->busy_urbs[channel]);
> +	if (mdev->padding_active[channel])
> +		mdev->padding_active[channel] = false;
> +
> +	if (mdev->conf[channel].data_type == MOST_CH_ASYNC) {
> +		del_timer_sync(&mdev->link_stat_timer);
> +		cancel_work_sync(&mdev->poll_work_obj);
> +	}
> +	mutex_unlock(&mdev->io_mutex);
> +	return 0;
> +}
> +
> +/**
> + * hdm_add_padding - add padding bytes
> + * @mdev: most device
> + * @channel: channel ID
> + * @mbo: buffer object
> + *
> + * This inserts the INIC hardware specific padding bytes into a streaming
> + * channel's buffer
> + */
> +static int hdm_add_padding(struct most_dev *mdev, int channel, struct mbo *mbo)
> +{
> +	struct most_channel_config *conf = &mdev->conf[channel];
> +	unsigned int frame_size = get_stream_frame_size(conf);
> +	unsigned int j, num_frames;
> +
> +	if (!frame_size)
> +		return -EINVAL;
> +	num_frames = mbo->buffer_length / frame_size;
> +
> +	if (num_frames < 1) {
> +		dev_err(&mdev->usb_device->dev,
> +			"Missed minimal transfer unit.\n");
> +		return -EINVAL;
> +	}
> +
> +	for (j = num_frames - 1; j > 0; j--)
> +		memmove(mbo->virt_address + j * USB_MTU,
> +			mbo->virt_address + j * frame_size,
> +			frame_size);
> +	mbo->buffer_length = num_frames * USB_MTU;
> +	return 0;
> +}
> +
> +/**
> + * hdm_remove_padding - remove padding bytes
> + * @mdev: most device
> + * @channel: channel ID
> + * @mbo: buffer object
> + *
> + * This takes the INIC hardware specific padding bytes off a streaming
> + * channel's buffer.
> + */
> +static int hdm_remove_padding(struct most_dev *mdev, int channel,
> +			      struct mbo *mbo)
> +{
> +	struct most_channel_config *const conf = &mdev->conf[channel];
> +	unsigned int frame_size = get_stream_frame_size(conf);
> +	unsigned int j, num_frames;
> +
> +	if (!frame_size)
> +		return -EINVAL;
> +	num_frames = mbo->processed_length / USB_MTU;
> +
> +	for (j = 1; j < num_frames; j++)
> +		memmove(mbo->virt_address + frame_size * j,
> +			mbo->virt_address + USB_MTU * j,
> +			frame_size);
> +
> +	mbo->processed_length = frame_size * num_frames;
> +	return 0;
> +}
> +
> +/**
> + * hdm_write_completion - completion function for submitted Tx URBs
> + * @urb: the URB that has been completed
> + *
> + * This checks the status of the completed URB. In case the URB has been
> + * unlinked before, it is immediately freed. On any other error the MBO
> + * transfer flag is set. On success it frees allocated resources and calls
> + * the completion function.
> + *
> + * Context: interrupt!
> + */
> +static void hdm_write_completion(struct urb *urb)
> +{
> +	struct mbo *mbo = urb->context;
> +	struct most_dev *mdev = to_mdev(mbo->ifp);
> +	unsigned int channel = mbo->hdm_channel_id;
> +	spinlock_t *lock = mdev->channel_lock + channel;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(lock, flags);
> +
> +	mbo->processed_length = 0;
> +	mbo->status = MBO_E_INVAL;
> +	if (likely(mdev->is_channel_healthy[channel])) {
> +		switch (urb->status) {
> +		case 0:
> +		case -ESHUTDOWN:
> +			mbo->processed_length = urb->actual_length;
> +			mbo->status = MBO_SUCCESS;
> +			break;
> +		case -EPIPE:
> +			dev_warn(&mdev->usb_device->dev,
> +				 "Broken pipe on ep%02x\n",
> +				 mdev->ep_address[channel]);
> +			mdev->is_channel_healthy[channel] = false;
> +			mdev->clear_work[channel].pipe = urb->pipe;
> +			schedule_work(&mdev->clear_work[channel].ws);
> +			break;
> +		case -ENODEV:
> +		case -EPROTO:
> +			mbo->status = MBO_E_CLOSE;
> +			break;
> +		}
> +	}
> +
> +	spin_unlock_irqrestore(lock, flags);
> +
> +	if (likely(mbo->complete))
> +		mbo->complete(mbo);
> +	usb_free_urb(urb);
> +}
> +
> +/**
> + * hdm_read_completion - completion function for submitted Rx URBs
> + * @urb: the URB that has been completed
> + *
> + * This checks the status of the completed URB. In case the URB has been
> + * unlinked before it is immediately freed. On any other error the MBO transfer
> + * flag is set. On success it frees allocated resources, removes
> + * padding bytes -if necessary- and calls the completion function.
> + *
> + * Context: interrupt!
> + *
> + * **************************************************************************
> + *                   Error codes returned by in urb->status
> + *                   or in iso_frame_desc[n].status (for ISO)
> + * *************************************************************************
> + *
> + * USB device drivers may only test urb status values in completion handlers.
> + * This is because otherwise there would be a race between HCDs updating
> + * these values on one CPU, and device drivers testing them on another CPU.
> + *
> + * A transfer's actual_length may be positive even when an error has been
> + * reported.  That's because transfers often involve several packets, so that
> + * one or more packets could finish before an error stops further endpoint I/O.
> + *
> + * For isochronous URBs, the urb status value is non-zero only if the URB is
> + * unlinked, the device is removed, the host controller is disabled or the total
> + * transferred length is less than the requested length and the URB_SHORT_NOT_OK
> + * flag is set.  Completion handlers for isochronous URBs should only see
> + * urb->status set to zero, -ENOENT, -ECONNRESET, -ESHUTDOWN, or -EREMOTEIO.
> + * Individual frame descriptor status fields may report more status codes.
> + *
> + *
> + * 0			Transfer completed successfully
> + *
> + * -ENOENT		URB was synchronously unlinked by usb_unlink_urb
> + *
> + * -EINPROGRESS		URB still pending, no results yet
> + *			(That is, if drivers see this it's a bug.)
> + *
> + * -EPROTO (*, **)	a) bitstuff error
> + *			b) no response packet received within the
> + *			   prescribed bus turn-around time
> + *			c) unknown USB error
> + *
> + * -EILSEQ (*, **)	a) CRC mismatch
> + *			b) no response packet received within the
> + *			   prescribed bus turn-around time
> + *			c) unknown USB error
> + *
> + *			Note that often the controller hardware does not
> + *			distinguish among cases a), b), and c), so a
> + *			driver cannot tell whether there was a protocol
> + *			error, a failure to respond (often caused by
> + *			device disconnect), or some other fault.
> + *
> + * -ETIME (**)		No response packet received within the prescribed
> + *			bus turn-around time.  This error may instead be
> + *			reported as -EPROTO or -EILSEQ.
> + *
> + * -ETIMEDOUT		Synchronous USB message functions use this code
> + *			to indicate timeout expired before the transfer
> + *			completed, and no other error was reported by HC.
> + *
> + * -EPIPE (**)		Endpoint stalled.  For non-control endpoints,
> + *			reset this status with usb_clear_halt().
> + *
> + * -ECOMM		During an IN transfer, the host controller
> + *			received data from an endpoint faster than it
> + *			could be written to system memory
> + *
> + * -ENOSR		During an OUT transfer, the host controller
> + *			could not retrieve data from system memory fast
> + *			enough to keep up with the USB data rate
> + *
> + * -EOVERFLOW (*)	The amount of data returned by the endpoint was
> + *			greater than either the max packet size of the
> + *			endpoint or the remaining buffer size.  "Babble".
> + *
> + * -EREMOTEIO		The data read from the endpoint did not fill the
> + *			specified buffer, and URB_SHORT_NOT_OK was set in
> + *			urb->transfer_flags.
> + *
> + * -ENODEV		Device was removed.  Often preceded by a burst of
> + *			other errors, since the hub driver doesn't detect
> + *			device removal events immediately.
> + *
> + * -EXDEV		ISO transfer only partially completed
> + *			(only set in iso_frame_desc[n].status, not urb->status)
> + *
> + * -EINVAL		ISO madness, if this happens: Log off and go home
> + *
> + * -ECONNRESET		URB was asynchronously unlinked by usb_unlink_urb
> + *
> + * -ESHUTDOWN		The device or host controller has been disabled due
> + *			to some problem that could not be worked around,
> + *			such as a physical disconnect.
> + *
> + *
> + * (*) Error codes like -EPROTO, -EILSEQ and -EOVERFLOW normally indicate
> + * hardware problems such as bad devices (including firmware) or cables.
> + *
> + * (**) This is also one of several codes that different kinds of host
> + * controller use to indicate a transfer has failed because of device
> + * disconnect.  In the interval before the hub driver starts disconnect
> + * processing, devices may receive such fault reports for every request.
> + *
> + * See <https://www.kernel.org/doc/Documentation/driver-api/usb/error-codes.rst>
> + */
> +static void hdm_read_completion(struct urb *urb)
> +{
> +	struct mbo *mbo = urb->context;
> +	struct most_dev *mdev = to_mdev(mbo->ifp);
> +	unsigned int channel = mbo->hdm_channel_id;
> +	struct device *dev = &mdev->usb_device->dev;
> +	spinlock_t *lock = mdev->channel_lock + channel;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(lock, flags);
> +
> +	mbo->processed_length = 0;
> +	mbo->status = MBO_E_INVAL;
> +	if (likely(mdev->is_channel_healthy[channel])) {
> +		switch (urb->status) {
> +		case 0:
> +		case -ESHUTDOWN:
> +			mbo->processed_length = urb->actual_length;
> +			mbo->status = MBO_SUCCESS;
> +			if (mdev->padding_active[channel] &&
> +			    hdm_remove_padding(mdev, channel, mbo)) {
> +				mbo->processed_length = 0;
> +				mbo->status = MBO_E_INVAL;
> +			}
> +			break;
> +		case -EPIPE:
> +			dev_warn(dev, "Broken pipe on ep%02x\n",
> +				 mdev->ep_address[channel]);
> +			mdev->is_channel_healthy[channel] = false;
> +			mdev->clear_work[channel].pipe = urb->pipe;
> +			schedule_work(&mdev->clear_work[channel].ws);
> +			break;
> +		case -ENODEV:
> +		case -EPROTO:
> +			mbo->status = MBO_E_CLOSE;
> +			break;
> +		case -EOVERFLOW:
> +			dev_warn(dev, "Babble on ep%02x\n",
> +				 mdev->ep_address[channel]);
> +			break;
> +		}
> +	}
> +
> +	spin_unlock_irqrestore(lock, flags);
> +
> +	if (likely(mbo->complete))
> +		mbo->complete(mbo);
> +	usb_free_urb(urb);
> +}
> +
> +/**
> + * hdm_enqueue - receive a buffer to be used for data transfer
> + * @iface: interface to enqueue to
> + * @channel: ID of the channel
> + * @mbo: pointer to the buffer object
> + *
> + * This allocates a new URB and fills it according to the channel
> + * that is being used for transmission of data. Before the URB is
> + * submitted it is stored in the private anchor list.
> + *
> + * Returns 0 on success. On any error the URB is freed and a error code
> + * is returned.
> + *
> + * Context: Could in _some_ cases be interrupt!
> + */
> +static int hdm_enqueue(struct most_interface *iface, int channel,
> +		       struct mbo *mbo)
> +{
> +	struct most_dev *mdev = to_mdev(iface);
> +	struct most_channel_config *conf;
> +	int retval = 0;
> +	struct urb *urb;
> +	unsigned long length;
> +	void *virt_address;
> +
> +	if (!mbo)
> +		return -EINVAL;
> +	if (iface->num_channels <= channel || channel < 0)
> +		return -ECHRNG;
> +
> +	conf = &mdev->conf[channel];
> +
> +	mutex_lock(&mdev->io_mutex);
> +	if (!mdev->usb_device) {
> +		retval = -ENODEV;
> +		goto unlock_io_mutex;
> +	}
> +
> +	urb = usb_alloc_urb(NO_ISOCHRONOUS_URB, GFP_ATOMIC);

You could move this before the mutex_lock().  Would GFP_ATOMIC still be
required?

> +	if (!urb) {
> +		retval = -ENOMEM;
> +		goto unlock_io_mutex;
> +	}
> +
> +	if ((conf->direction & MOST_CH_TX) && mdev->padding_active[channel] &&
> +	    hdm_add_padding(mdev, channel, mbo)) {
> +		retval = -EINVAL;
> +		goto err_free_urb;
> +	}
> +
> +	urb->transfer_dma = mbo->bus_address;
> +	virt_address = mbo->virt_address;
> +	length = mbo->buffer_length;
> +
> +	if (conf->direction & MOST_CH_TX) {
> +		usb_fill_bulk_urb(urb, mdev->usb_device,
> +				  usb_sndbulkpipe(mdev->usb_device,
> +						  mdev->ep_address[channel]),
> +				  virt_address,
> +				  length,
> +				  hdm_write_completion,
> +				  mbo);
> +		if (conf->data_type != MOST_CH_ISOC &&
> +		    conf->data_type != MOST_CH_SYNC)
> +			urb->transfer_flags |= URB_ZERO_PACKET;
> +	} else {
> +		usb_fill_bulk_urb(urb, mdev->usb_device,
> +				  usb_rcvbulkpipe(mdev->usb_device,
> +						  mdev->ep_address[channel]),
> +				  virt_address,
> +				  length + conf->extra_len,
> +				  hdm_read_completion,
> +				  mbo);
> +	}
> +	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
> +
> +	usb_anchor_urb(urb, &mdev->busy_urbs[channel]);
> +
> +	retval = usb_submit_urb(urb, GFP_KERNEL);
> +	if (retval) {
> +		dev_err(&mdev->usb_device->dev,
> +			"URB submit failed with error %d.\n", retval);
> +		goto err_unanchor_urb;
> +	}
> +	goto unlock_io_mutex;

Replace the goto with:

	mutex_unlock(&mdev->io_mutex);
	return 0;

It lets you move the lock around more easily.

> +
> +err_unanchor_urb:
> +	usb_unanchor_urb(urb);
> +err_free_urb:
> +	usb_free_urb(urb);
> +unlock_io_mutex:
> +	mutex_unlock(&mdev->io_mutex);
> +	return retval;
> +}
> +
> +static void *hdm_dma_alloc(struct mbo *mbo, u32 size)
> +{
> +	struct most_dev *mdev = to_mdev(mbo->ifp);
> +
> +	return usb_alloc_coherent(mdev->usb_device, size, GFP_KERNEL,
> +				  &mbo->bus_address);
> +}
> +
> +static void hdm_dma_free(struct mbo *mbo, u32 size)
> +{
> +	struct most_dev *mdev = to_mdev(mbo->ifp);
> +
> +	usb_free_coherent(mdev->usb_device, size, mbo->virt_address,
> +			  mbo->bus_address);
> +}
> +
> +/**
> + * hdm_configure_channel - receive channel configuration from core
> + * @iface: interface
> + * @channel: channel ID
> + * @conf: structure that holds the configuration information
> + *
> + * The attached network interface controller (NIC) supports a padding mode
> + * to avoid short packets on USB, hence increasing the performance due to a
> + * lower interrupt load. This mode is default for synchronous data and can
> + * be switched on for isochronous data. In case padding is active the
> + * driver needs to know the frame size of the payload in order to calculate
> + * the number of bytes it needs to pad when transmitting or to cut off when
> + * receiving data.
> + *
> + */
> +static int hdm_configure_channel(struct most_interface *iface, int channel,
> +				 struct most_channel_config *conf)
> +{
> +	unsigned int num_frames;
> +	unsigned int frame_size;
> +	struct most_dev *mdev = to_mdev(iface);
> +	struct device *dev = &mdev->usb_device->dev;
> +
> +	mdev->is_channel_healthy[channel] = true;
> +	mdev->clear_work[channel].channel = channel;
> +	mdev->clear_work[channel].mdev = mdev;
> +	INIT_WORK(&mdev->clear_work[channel].ws, wq_clear_halt);
> +
> +	if (!conf) {
> +		dev_err(dev, "Bad config pointer.\n");
> +		return -EINVAL;
> +	}
> +	if (channel < 0 || channel >= iface->num_channels) {
> +		dev_err(dev, "Channel ID out of range.\n");
> +		return -EINVAL;
> +	}
> +	if (!conf->num_buffers || !conf->buffer_size) {
> +		dev_err(dev, "Misconfig: buffer size or #buffers zero.\n");
> +		return -EINVAL;
> +	}
> +
> +	if (conf->data_type != MOST_CH_SYNC &&
> +	    !(conf->data_type == MOST_CH_ISOC &&
> +	      conf->packets_per_xact != 0xFF)) {
> +		mdev->padding_active[channel] = false;
> +		/*
> +		 * Since the NIC's padding mode is not going to be
> +		 * used, we can skip the frame size calculations and
> +		 * move directly on to exit.
> +		 */

I absolutely hate that we're skipping the other checks...  At least
zero out the frame size information so that we don't save invalid data.

> +		goto exit;
> +	}
> +
> +	mdev->padding_active[channel] = true;
> +
> +	frame_size = get_stream_frame_size(conf);
> +	if (frame_size == 0 || frame_size > USB_MTU) {
> +		dev_warn(dev, "Misconfig: frame size wrong\n");
> +		return -EINVAL;
> +	}
> +
> +	num_frames = conf->buffer_size / frame_size;
> +
> +	if (conf->buffer_size % frame_size) {
> +		u16 old_size = conf->buffer_size;
> +
> +		conf->buffer_size = num_frames * frame_size;
> +		dev_warn(dev, "%s: fixed buffer size (%d -> %d)\n",
> +			 mdev->suffix[channel], old_size, conf->buffer_size);
> +	}
> +
> +	/* calculate extra length to comply w/ HW padding */
> +	conf->extra_len = num_frames * (USB_MTU - frame_size);
> +
> +exit:
> +	mdev->conf[channel] = *conf;
> +	if (conf->data_type == MOST_CH_ASYNC) {
> +		u16 ep = mdev->ep_address[channel];
> +
> +		if (start_sync_ep(mdev->usb_device, ep) < 0)
> +			dev_warn(dev, "sync for ep%02x failed", ep);
> +	}
> +	return 0;
> +}
> +
> +/**
> + * hdm_request_netinfo - request network information
> + * @iface: pointer to interface
> + * @channel: channel ID
> + *
> + * This is used as trigger to set up the link status timer that
> + * polls for the NI state of the INIC every 2 seconds.
> + *
> + */
> +static void hdm_request_netinfo(struct most_interface *iface, int channel,
> +				void (*on_netinfo)(struct most_interface *,
> +						   unsigned char,
> +						   unsigned char *))
> +{
> +	struct most_dev *mdev = to_mdev(iface);
> +
> +	mdev->on_netinfo = on_netinfo;
> +	if (!on_netinfo)
> +		return;
> +
> +	mdev->link_stat_timer.expires = jiffies + HZ;
> +	mod_timer(&mdev->link_stat_timer, mdev->link_stat_timer.expires);
> +}
> +
> +/**
> + * link_stat_timer_handler - schedule work obtaining mac address and link status
> + * @data: pointer to USB device instance
> + *
> + * The handler runs in interrupt context. That's why we need to defer the
> + * tasks to a work queue.
> + */
> +static void link_stat_timer_handler(struct timer_list *t)
> +{
> +	struct most_dev *mdev = from_timer(mdev, t, link_stat_timer);
> +
> +	schedule_work(&mdev->poll_work_obj);
> +	mdev->link_stat_timer.expires = jiffies + (2 * HZ);
> +	add_timer(&mdev->link_stat_timer);
> +}
> +
> +/**
> + * wq_netinfo - work queue function to deliver latest networking information
> + * @wq_obj: object that holds data for our deferred work to do
> + *
> + * This retrieves the network interface status of the USB INIC
> + */
> +static void wq_netinfo(struct work_struct *wq_obj)
> +{
> +	struct most_dev *mdev = to_mdev_from_work(wq_obj);
> +	struct usb_device *usb_device = mdev->usb_device;
> +	struct device *dev = &usb_device->dev;
> +	u16 hi, mi, lo, link;
> +	u8 hw_addr[6];
> +
> +	if (drci_rd_reg(usb_device, DRCI_REG_HW_ADDR_HI, &hi) < 0) {
> +		dev_err(dev, "Vendor request 'hw_addr_hi' failed\n");
> +		return;
> +	}
> +
> +	if (drci_rd_reg(usb_device, DRCI_REG_HW_ADDR_MI, &mi) < 0) {
> +		dev_err(dev, "Vendor request 'hw_addr_mid' failed\n");
> +		return;
> +	}
> +
> +	if (drci_rd_reg(usb_device, DRCI_REG_HW_ADDR_LO, &lo) < 0) {
> +		dev_err(dev, "Vendor request 'hw_addr_low' failed\n");
> +		return;
> +	}
> +
> +	if (drci_rd_reg(usb_device, DRCI_REG_NI_STATE, &link) < 0) {
> +		dev_err(dev, "Vendor request 'link status' failed\n");
> +		return;
> +	}
> +
> +	hw_addr[0] = hi >> 8;
> +	hw_addr[1] = hi;
> +	hw_addr[2] = mi >> 8;
> +	hw_addr[3] = mi;
> +	hw_addr[4] = lo >> 8;
> +	hw_addr[5] = lo;
> +
> +	if (mdev->on_netinfo)
> +		mdev->on_netinfo(&mdev->iface, link, hw_addr);
> +}
> +
> +/**
> + * wq_clear_halt - work queue function
> + * @wq_obj: work_struct object to execute
> + *
> + * This sends a clear_halt to the given USB pipe.
> + */
> +static void wq_clear_halt(struct work_struct *wq_obj)
> +{
> +	struct clear_hold_work *clear_work = to_clear_hold_work(wq_obj);
> +	struct most_dev *mdev = clear_work->mdev;
> +	unsigned int channel = clear_work->channel;
> +	int pipe = clear_work->pipe;
> +
> +	mutex_lock(&mdev->io_mutex);
> +	most_stop_enqueue(&mdev->iface, channel);
> +	usb_kill_anchored_urbs(&mdev->busy_urbs[channel]);
> +	if (usb_clear_halt(mdev->usb_device, pipe))
> +		dev_warn(&mdev->usb_device->dev, "Failed to reset endpoint.\n");
> +
> +	/* If the functional Stall condition has been set on an
> +	 * asynchronous rx channel, we need to clear the tx channel
> +	 * too, since the hardware runs its clean-up sequence on both
> +	 * channels, as they are physically one on the network.
> +	 *
> +	 * The USB interface that exposes the asynchronous channels
> +	 * contains always two endpoints, and two only.
> +	 */
> +	if (mdev->conf[channel].data_type == MOST_CH_ASYNC &&
> +	    mdev->conf[channel].direction == MOST_CH_RX) {
> +		int peer = 1 - channel;
                ^^^^^^^^^^^^^^^^^^^^^^
This is too tricky.  At the start of the function channel seems to be a
number between 0-30 so this looks like "peer" can be negative.
Presumably, only the first two channels are MOST_CH_ASYNC and MOST_CH_RX?

But could we just write it like:

		if (channel == 0)
			peer = 1;
		else
			peer = 0;


> +		int snd_pipe = usb_sndbulkpipe(mdev->usb_device,
> +					       mdev->ep_address[peer]);
> +		usb_clear_halt(mdev->usb_device, snd_pipe);
> +	}
> +	mdev->is_channel_healthy[channel] = true;
> +	most_resume_enqueue(&mdev->iface, channel);
> +	mutex_unlock(&mdev->io_mutex);
> +}
> +
> +/**
> + * hdm_usb_fops - file operation table for USB driver
> + */
> +static const struct file_operations hdm_usb_fops = {
> +	.owner = THIS_MODULE,
> +};
> +
> +/**
> + * usb_device_id - ID table for HCD device probing
> + */
> +static const struct usb_device_id usbid[] = {
> +	{ USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_BRDG), },
> +	{ USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_OS81118), },
> +	{ USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_OS81119), },
> +	{ USB_DEVICE(USB_VENDOR_ID_SMSC, USB_DEV_ID_OS81210), },
> +	{ } /* Terminating entry */
> +};
> +
> +struct regs {
> +	const char *name;
> +	u16 reg;
> +};
> +
> +static const struct regs ro_regs[] = {
> +	{ "ni_state", DRCI_REG_NI_STATE },
> +	{ "packet_bandwidth", DRCI_REG_PACKET_BW },
> +	{ "node_address", DRCI_REG_NODE_ADDR },
> +	{ "node_position", DRCI_REG_NODE_POS },
> +};
> +
> +static const struct regs rw_regs[] = {
> +	{ "mep_filter", DRCI_REG_MEP_FILTER },
> +	{ "mep_hash0", DRCI_REG_HASH_TBL0 },
> +	{ "mep_hash1", DRCI_REG_HASH_TBL1 },
> +	{ "mep_hash2", DRCI_REG_HASH_TBL2 },
> +	{ "mep_hash3", DRCI_REG_HASH_TBL3 },
> +	{ "mep_eui48_hi", DRCI_REG_HW_ADDR_HI },
> +	{ "mep_eui48_mi", DRCI_REG_HW_ADDR_MI },
> +	{ "mep_eui48_lo", DRCI_REG_HW_ADDR_LO },
> +};
> +
> +static int get_stat_reg_addr(const struct regs *regs, int size,
> +			     const char *name, u16 *reg_addr)
> +{
> +	int i;
> +
> +	for (i = 0; i < size; i++) {
> +		if (!strcmp(name, regs[i].name)) {
> +			*reg_addr = regs[i].reg;
> +			return 0;
> +		}
> +	}
> +	return -EFAULT;

This should be -EINVAL

> +}
> +
> +#define get_static_reg_addr(regs, name, reg_addr) \
> +	get_stat_reg_addr(regs, ARRAY_SIZE(regs), name, reg_addr)
> +
> +static ssize_t value_show(struct device *dev, struct device_attribute *attr,
> +			  char *buf)
> +{
> +	const char *name = attr->attr.name;
> +	struct most_dci_obj *dci_obj = to_dci_obj(dev);
> +	u16 val;
> +	u16 reg_addr;
> +	int err;
> +
> +	if (!strcmp(name, "arb_address"))

I feel like most of these strcmp() should be sysfs_streq().

> +		return snprintf(buf, PAGE_SIZE, "%04x\n", dci_obj->reg_addr);
> +
> +	if (!strcmp(name, "arb_value"))
> +		reg_addr = dci_obj->reg_addr;
> +	else if (get_static_reg_addr(ro_regs, name, &reg_addr) &&
> +		 get_static_reg_addr(rw_regs, name, &reg_addr))
> +		return -EFAULT;

-EINVAL

> +
> +	err = drci_rd_reg(dci_obj->usb_device, reg_addr, &val);
> +	if (err < 0)
> +		return err;
> +
> +	return snprintf(buf, PAGE_SIZE, "%04x\n", val);
> +}
> +
> +static ssize_t value_store(struct device *dev, struct device_attribute *attr,
> +			   const char *buf, size_t count)
> +{
> +	u16 val;
> +	u16 reg_addr;
> +	const char *name = attr->attr.name;
> +	struct most_dci_obj *dci_obj = to_dci_obj(dev);
> +	struct usb_device *usb_dev = dci_obj->usb_device;
> +	int err = kstrtou16(buf, 16, &val);

Could we move function calls which can fail out of the declaration block?
Otherwise there is a blank or worse between the call and the error
check.

> +
> +	if (err)
> +		return err;
> +
> +	if (!strcmp(name, "arb_address")) {

Use sysfs_streq()?

> +		dci_obj->reg_addr = val;
> +		return count;
> +	}
> +
> +	if (!strcmp(name, "arb_value"))
> +		err = drci_wr_reg(usb_dev, dci_obj->reg_addr, val);
> +	else if (!strcmp(name, "sync_ep"))
> +		err = start_sync_ep(usb_dev, val);
> +	else if (!get_static_reg_addr(rw_regs, name, &reg_addr))
> +		err = drci_wr_reg(usb_dev, reg_addr, val);
> +	else
> +		return -EFAULT;

A lot of -EFAULT should be changed to -EINVAL.  Search for it everywhere,
please.

> +
> +	if (err < 0)
> +		return err;
> +
> +	return count;
> +}
> +
> +static DEVICE_ATTR(ni_state, 0444, value_show, NULL);
> +static DEVICE_ATTR(packet_bandwidth, 0444, value_show, NULL);
> +static DEVICE_ATTR(node_address, 0444, value_show, NULL);
> +static DEVICE_ATTR(node_position, 0444, value_show, NULL);
> +static DEVICE_ATTR(sync_ep, 0200, NULL, value_store);
> +static DEVICE_ATTR(mep_filter, 0644, value_show, value_store);
> +static DEVICE_ATTR(mep_hash0, 0644, value_show, value_store);
> +static DEVICE_ATTR(mep_hash1, 0644, value_show, value_store);
> +static DEVICE_ATTR(mep_hash2, 0644, value_show, value_store);
> +static DEVICE_ATTR(mep_hash3, 0644, value_show, value_store);
> +static DEVICE_ATTR(mep_eui48_hi, 0644, value_show, value_store);
> +static DEVICE_ATTR(mep_eui48_mi, 0644, value_show, value_store);
> +static DEVICE_ATTR(mep_eui48_lo, 0644, value_show, value_store);
> +static DEVICE_ATTR(arb_address, 0644, value_show, value_store);
> +static DEVICE_ATTR(arb_value, 0644, value_show, value_store);
> +
> +static struct attribute *dci_attrs[] = {
> +	&dev_attr_ni_state.attr,
> +	&dev_attr_packet_bandwidth.attr,
> +	&dev_attr_node_address.attr,
> +	&dev_attr_node_position.attr,
> +	&dev_attr_sync_ep.attr,
> +	&dev_attr_mep_filter.attr,
> +	&dev_attr_mep_hash0.attr,
> +	&dev_attr_mep_hash1.attr,
> +	&dev_attr_mep_hash2.attr,
> +	&dev_attr_mep_hash3.attr,
> +	&dev_attr_mep_eui48_hi.attr,
> +	&dev_attr_mep_eui48_mi.attr,
> +	&dev_attr_mep_eui48_lo.attr,
> +	&dev_attr_arb_address.attr,
> +	&dev_attr_arb_value.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group dci_attr_group = {
> +	.attrs = dci_attrs,
> +};
> +
> +static const struct attribute_group *dci_attr_groups[] = {
> +	&dci_attr_group,
> +	NULL,
> +};
> +
> +static void release_dci(struct device *dev)
> +{
> +	struct most_dci_obj *dci = to_dci_obj(dev);
> +
> +	kfree(dci);
> +}
> +
> +static void release_mdev(struct device *dev)
> +{
> +	struct most_dev *mdev = to_mdev_from_dev(dev);
> +
> +	kfree(mdev);
> +}
> +/**
> + * hdm_probe - probe function of USB device driver
> + * @interface: Interface of the attached USB device
> + * @id: Pointer to the USB ID table.
> + *
> + * This allocates and initializes the device instance, adds the new
> + * entry to the internal list, scans the USB descriptors and registers
> + * the interface with the core.
> + * Additionally, the DCI objects are created and the hardware is sync'd.
> + *
> + * Return 0 on success. In case of an error a negative number is returned.
> + */
> +static int
> +hdm_probe(struct usb_interface *interface, const struct usb_device_id *id)
> +{
> +	struct usb_host_interface *usb_iface_desc = interface->cur_altsetting;
> +	struct usb_device *usb_dev = interface_to_usbdev(interface);
> +	struct device *dev = &usb_dev->dev;
> +	struct most_dev *mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
> +	unsigned int i;
> +	unsigned int num_endpoints;
> +	struct most_channel_capability *tmp_cap;
> +	struct usb_endpoint_descriptor *ep_desc;
> +	int ret = 0;
> +
> +	if (!mdev)
> +		goto err_out_of_memory;

The "goto" checks for if err isn't set an defaults to -ENOMEM.  Please
just set the error code.  But actually here the appropriate thing is
to just return directly:

	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
	if (!mdev)
		return -ENOMEM;

> +
> +	usb_set_intfdata(interface, mdev);
> +	num_endpoints = usb_iface_desc->desc.bNumEndpoints;
> +	mutex_init(&mdev->io_mutex);
> +	INIT_WORK(&mdev->poll_work_obj, wq_netinfo);
> +	timer_setup(&mdev->link_stat_timer, link_stat_timer_handler, 0);
> +
> +	mdev->usb_device = usb_dev;
> +	mdev->link_stat_timer.expires = jiffies + (2 * HZ);
> +
> +	mdev->iface.mod = hdm_usb_fops.owner;
> +	mdev->iface.dev = &mdev->dev;
> +	mdev->iface.driver_dev = &interface->dev;
> +	mdev->iface.interface = ITYPE_USB;
> +	mdev->iface.configure = hdm_configure_channel;
> +	mdev->iface.request_netinfo = hdm_request_netinfo;
> +	mdev->iface.enqueue = hdm_enqueue;
> +	mdev->iface.poison_channel = hdm_poison_channel;
> +	mdev->iface.dma_alloc = hdm_dma_alloc;
> +	mdev->iface.dma_free = hdm_dma_free;
> +	mdev->iface.description = mdev->description;
> +	mdev->iface.num_channels = num_endpoints;
> +
> +	snprintf(mdev->description, sizeof(mdev->description),
> +		 "%d-%s:%d.%d",
> +		 usb_dev->bus->busnum,
> +		 usb_dev->devpath,
> +		 usb_dev->config->desc.bConfigurationValue,
> +		 usb_iface_desc->desc.bInterfaceNumber);
> +
> +	mdev->dev.init_name = mdev->description;
> +	mdev->dev.parent = &interface->dev;
> +	mdev->dev.release = release_mdev;
> +	mdev->conf = kcalloc(num_endpoints, sizeof(*mdev->conf), GFP_KERNEL);
> +	if (!mdev->conf)
> +		goto err_free_mdev;
> +
> +	mdev->cap = kcalloc(num_endpoints, sizeof(*mdev->cap), GFP_KERNEL);
> +	if (!mdev->cap)
> +		goto err_free_conf;
> +
> +	mdev->iface.channel_vector = mdev->cap;
> +	mdev->ep_address = kcalloc(num_endpoints, sizeof(*mdev->ep_address), GFP_KERNEL);
> +	if (!mdev->ep_address)
> +		goto err_free_cap;
> +
> +	mdev->busy_urbs = kcalloc(num_endpoints, sizeof(*mdev->busy_urbs), GFP_KERNEL);
> +	if (!mdev->busy_urbs)
> +		goto err_free_ep_address;
> +
> +	tmp_cap = mdev->cap;
> +	for (i = 0; i < num_endpoints; i++) {
> +		ep_desc = &usb_iface_desc->endpoint[i].desc;
> +		mdev->ep_address[i] = ep_desc->bEndpointAddress;
> +		mdev->padding_active[i] = false;
> +		mdev->is_channel_healthy[i] = true;
> +
> +		snprintf(&mdev->suffix[i][0], MAX_SUFFIX_LEN, "ep%02x",
> +			 mdev->ep_address[i]);
> +
> +		tmp_cap->name_suffix = &mdev->suffix[i][0];
> +		tmp_cap->buffer_size_packet = MAX_BUF_SIZE;
> +		tmp_cap->buffer_size_streaming = MAX_BUF_SIZE;
> +		tmp_cap->num_buffers_packet = BUF_CHAIN_SIZE;
> +		tmp_cap->num_buffers_streaming = BUF_CHAIN_SIZE;
> +		tmp_cap->data_type = MOST_CH_CONTROL | MOST_CH_ASYNC |
> +				     MOST_CH_ISOC | MOST_CH_SYNC;
> +		if (usb_endpoint_dir_in(ep_desc))
> +			tmp_cap->direction = MOST_CH_RX;
> +		else
> +			tmp_cap->direction = MOST_CH_TX;
> +		tmp_cap++;
> +		init_usb_anchor(&mdev->busy_urbs[i]);
> +		spin_lock_init(&mdev->channel_lock[i]);
> +	}
> +	dev_notice(dev, "claimed gadget: Vendor=%4.4x ProdID=%4.4x Bus=%02x Device=%02x\n",
> +		   le16_to_cpu(usb_dev->descriptor.idVendor),
> +		   le16_to_cpu(usb_dev->descriptor.idProduct),
> +		   usb_dev->bus->busnum,
> +		   usb_dev->devnum);
> +
> +	dev_notice(dev, "device path: /sys/bus/usb/devices/%d-%s:%d.%d\n",
> +		   usb_dev->bus->busnum,
> +		   usb_dev->devpath,
> +		   usb_dev->config->desc.bConfigurationValue,
> +		   usb_iface_desc->desc.bInterfaceNumber);
> +
> +	ret = most_register_interface(&mdev->iface);
> +	if (ret)
> +		goto err_free_busy_urbs;
> +
> +	mutex_lock(&mdev->io_mutex);
> +	if (le16_to_cpu(usb_dev->descriptor.idProduct) == USB_DEV_ID_OS81118 ||
> +	    le16_to_cpu(usb_dev->descriptor.idProduct) == USB_DEV_ID_OS81119 ||
> +	    le16_to_cpu(usb_dev->descriptor.idProduct) == USB_DEV_ID_OS81210) {
> +		mdev->dci = kzalloc(sizeof(*mdev->dci), GFP_KERNEL);
> +		if (!mdev->dci) {
> +			mutex_unlock(&mdev->io_mutex);
> +			most_deregister_interface(&mdev->iface);

Free iface after the goto.

> +			ret = -ENOMEM;
> +			goto err_free_busy_urbs;
> +		}
> +
> +		mdev->dci->dev.init_name = "dci";
> +		mdev->dci->dev.parent = get_device(mdev->iface.dev);
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Does this get_device() need a matching put_device() somewhere?  I'm not
totally sure how the ->parent stuff works...

> +		mdev->dci->dev.groups = dci_attr_groups;
> +		mdev->dci->dev.release = release_dci;
> +		if (device_register(&mdev->dci->dev)) {
> +			mutex_unlock(&mdev->io_mutex);
> +			most_deregister_interface(&mdev->iface);
> +			ret = -ENOMEM;
> +			goto err_free_dci;
> +		}
> +		mdev->dci->usb_device = mdev->usb_device;
> +	}
> +	mutex_unlock(&mdev->io_mutex);
> +	return 0;
> +err_free_dci:
> +	put_device(&mdev->dci->dev);
> +err_free_busy_urbs:
> +	kfree(mdev->busy_urbs);
> +err_free_ep_address:
> +	kfree(mdev->ep_address);
> +err_free_cap:
> +	kfree(mdev->cap);
> +err_free_conf:
> +	kfree(mdev->conf);
> +err_free_mdev:
> +	put_device(&mdev->dev);
> +err_out_of_memory:
> +	if (ret == 0 || ret == -ENOMEM) {
> +		ret = -ENOMEM;
> +		dev_err(dev, "out of memory\n");
> +	}
> +	return ret;
> +}

regards,
dan carpenter

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