Re: [PATCH 1/3] usb: add support for Diolan DLN-2 devices

[Johan Hovold <johan@kernel.org>]

On Wed, Aug 20, 2014 at 02:24:45PM +0300, Daniel Baluta wrote:
> From: Octavian Purdila <octavian.purdila@intel.com>
> 
> This patch implements the USB part of the Diolan USB-I2C/SPI/GPIO
> Master Adapter DLN-2. Details about the device can be found here:
> 
> https://www.diolan.com/i2c/i2c_interface.html.
> 
> Information about the USB protocol can be found in the Programmer's
> Reference Manual [1], see section 1.7.
> 
> Because the hardware has a single transmit endpoint and a single
> receive endpoint the communication between the various DLN2 drivers
> and the hardware will be muxed/demuxed by this driver.
> 
> The functional DLN2 drivers (i2c, GPIO, etc.) will have to register
> themselves as DLN2 modules in order to send or receive data.
> 
> Each DLN2 module will be identified by the handle field within the DLN2
> message header. If a DLN2 module issues multiple commands in parallel
> they will be identified by the echo counter field in the message header.
> 
> The DLN2 modules can use the dln2_transfer() function to issue a
> command and wait for its response. They can also use an asynchronous
> mode of operation, in which case a receive callback function is going
> to be notified when messages for a specific handle are received.
> 
> Because the hardware reserves handle 0 for GPIO events, the driver
> also reserves handle 0. It will be allocated to a DLN2 module only if
> it is explicitly requested.
> 
> [1] https://www.diolan.com/downloads/dln-api-manual.pdf
> 
> Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
> ---
>  drivers/usb/misc/Kconfig  |   6 +
>  drivers/usb/misc/Makefile |   1 +
>  drivers/usb/misc/dln2.c   | 719 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/usb/dln2.h  | 146 ++++++++++
>  4 files changed, 872 insertions(+)
>  create mode 100644 drivers/usb/misc/dln2.c
>  create mode 100644 include/linux/usb/dln2.h
> 
> diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
> index 76d7720..953f521 100644
> --- a/drivers/usb/misc/Kconfig
> +++ b/drivers/usb/misc/Kconfig
> @@ -255,3 +255,9 @@ config USB_LINK_LAYER_TEST
>  	  This driver is for generating specific traffic for Super Speed Link
>  	  Layer Test Device. Say Y only when you want to conduct USB Super Speed
>  	  Link Layer Test for host controllers.
> +
> +config USB_DLN2
> +	tristate "Diolan DLN2 USB Driver"
> +	help
> +	  This adds USB support for Diolan  USB-I2C/SPI/GPIO
> +	  Master Adapter DLN-2.
> diff --git a/drivers/usb/misc/Makefile b/drivers/usb/misc/Makefile
> index 65b0402..767264e 100644
> --- a/drivers/usb/misc/Makefile
> +++ b/drivers/usb/misc/Makefile
> @@ -25,6 +25,7 @@ obj-$(CONFIG_USB_USS720)		+= uss720.o
>  obj-$(CONFIG_USB_SEVSEG)		+= usbsevseg.o
>  obj-$(CONFIG_USB_YUREX)			+= yurex.o
>  obj-$(CONFIG_USB_HSIC_USB3503)		+= usb3503.o
> +obj-$(CONFIG_USB_DLN2)			+= dln2.o
>  
>  obj-$(CONFIG_USB_SISUSBVGA)		+= sisusbvga/
>  obj-$(CONFIG_USB_LINK_LAYER_TEST)	+= lvstest.o
> diff --git a/drivers/usb/misc/dln2.c b/drivers/usb/misc/dln2.c
> new file mode 100644
> index 0000000..5bfa850
> --- /dev/null
> +++ b/drivers/usb/misc/dln2.c
> @@ -0,0 +1,719 @@
> +/*
> + * Driver for the Diolan DLN-2 USB adapter
> + *
> + * Copyright (c) 2014 Intel Corporation
> + *
> + * Derived from:
> + *  i2c-diolan-u2c.c
> + *  Copyright (c) 2010-2011 Ericsson AB
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation, version 2.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/module.h>
> +#include <linux/types.h>
> +#include <linux/slab.h>
> +#include <linux/usb.h>
> +#include <linux/i2c.h>
> +#include <linux/mutex.h>
> +
> +#define DRIVER_NAME			"usb-dln2"
> +
> +#define DLN2_GENERIC_MODULE_ID		0x00
> +#define DLN2_GENERIC_CMD(cmd)		DLN2_CMD(cmd, DLN2_GENERIC_MODULE_ID)
> +
> +/* generic commands */
> +#define CMD_GET_DEVICE_VER		DLN2_GENERIC_CMD(0x30)
> +#define CMD_GET_DEVICE_SN		DLN2_GENERIC_CMD(0x31)

Have you considered using regmap for register access?

> +
> +#define DLN2_HW_ID			0x200
> +
> +#define DLN2_USB_TIMEOUT		100	/* in ms */
> +
> +#define DLN2_MAX_RX_SLOTS 16
> +
> +#include <linux/usb/dln2.h>

Move to the other includes.

> +
> +struct dln2_rx_context {
> +	struct completion done;
> +	struct urb *urb;
> +	bool connected;
> +};
> +
> +struct dln2_rx_slots {
> +	/* RX slots bitmap */
> +	DECLARE_BITMAP(bmap, DLN2_MAX_RX_SLOTS);

You only have 16 slots and only do single bit manipulations. Just use an
unsigned long and find_first_bit, set_bit, etc, below.

> +
> +	/* used to wait for a free RX slot */
> +	wait_queue_head_t wq;
> +
> +	/* used to wait for an RX operation to complete */
> +	struct dln2_rx_context slots[DLN2_MAX_RX_SLOTS];
> +
> +	/* avoid races between free_rx_slot and dln2_transfer_rx_cb */
> +	spinlock_t lock;
> +};
> +
> +static int find_free_slot(struct dln2_rx_slots *rxs, int *slot)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&rxs->lock, flags);
> +
> +	*slot = bitmap_find_free_region(rxs->bmap, DLN2_MAX_RX_SLOTS, 0) - 1;
> +
> +	if (*slot >= 0) {
> +		struct dln2_rx_context *rxc = &rxs->slots[*slot];
> +
> +		init_completion(&rxc->done);
> +		rxc->connected = true;
> +	}
> +
> +	spin_unlock_irqrestore(&rxs->lock, flags);
> +
> +	return *slot >= 0;
> +}
> +
> +static int alloc_rx_slot(struct dln2_rx_slots *rxs)
> +{
> +	int slot, ret;
> +
> +	ret = wait_event_interruptible(rxs->wq, find_free_slot(rxs, &slot));

You probably want a timeout here as well.

> +	if (ret < 0)
> +		return ret;
> +
> +	return slot;
> +}
> +
> +static void free_rx_slot(struct dln2_rx_slots *rxs, int slot)
> +{
> +	unsigned long flags;
> +	struct dln2_rx_context *rxc;
> +
> +	spin_lock_irqsave(&rxs->lock, flags);
> +
> +	bitmap_clear(rxs->bmap, slot + 1, 1);
> +
> +	rxc = &rxs->slots[slot];
> +	rxc->connected = false;
> +
> +	if (rxc->urb) {
> +		usb_submit_urb(rxc->urb, GFP_KERNEL);

You cannot use GFP_KERNEL in atomic context.

Error handling is missing.

> +		rxc->urb = NULL;
> +	}
> +
> +	spin_unlock_irqrestore(&rxs->lock, flags);
> +
> +	wake_up_interruptible(&rxs->wq);
> +}
> +
> +
> +#define DLN2_MAX_MODULES	5
> +#define DLN2_MAX_URBS		16
> +
> +struct dln2_dev {
> +	struct urb *rx_urb[DLN2_MAX_URBS];
> +	void *rx_buf[DLN2_MAX_URBS];
> +	int ep_in, ep_out;              /* Endpoints    */

One declaration per line, and endpoint addresses are unsigned -- u8 will
do.

Skip the comment.

> +	struct usb_device *usb_dev;	/* the usb device for this device */
> +	struct usb_interface *interface;/* the interface for this device */

Do the comments really add anything here?

> +
> +	struct dln2_rx_slots mod_rx_slots[DLN2_MAX_MODULES];
> +	void *context[DLN2_MAX_MODULES];
> +	bool mod_initialized[DLN2_MAX_MODULES];
> +
> +	struct list_head list;
> +};
> +
> +struct dln2_mod {
> +	struct dln2_mod_ops *ops;
> +	void *context;
> +};
> +
> +/* registered modules (e.g i2c, GPIO, GPIO interrupts, etc.) */
> +static struct dln2_mod dln2_modules[DLN2_MAX_MODULES];
> +static DEFINE_MUTEX(dln2_modules_mutex);
> +/* module used internally for control messages */
> +static struct dln2_mod *dln2_ctrl_mod;
> +
> +static inline int dln2_get_handle(struct dln2_mod *mod)
> +{
> +	int handle = mod - dln2_modules;
> +
> +	BUG_ON(handle < 0 || handle > DLN2_MAX_MODULES);

Don't use BUG(). It's really not nice to kill the user's machine for
this. Handle at the call site instead.

> +
> +	return handle;
> +}
> +
> +static void dln2_connect_do_work(struct work_struct *w);
> +static DECLARE_DELAYED_WORK(dln2_connect_work, dln2_connect_do_work);
> +
> +struct dln2_mod *dln2_register_module(int handle, struct dln2_mod_ops *mod_ops)
> +{
> +	int i;
> +
> +	if (!mod_ops)
> +		return ERR_PTR(-EINVAL);
> +
> +	mutex_lock(&dln2_modules_mutex);
> +
> +	if (handle < 0) {
> +		for (i = 0; i < DLN2_MAX_MODULES; i++) {
> +			/* reserve handle 0 for GPIO interrupts */
> +			if (!dln2_modules[i].ops && i > 0) {
> +				handle = i;
> +				break;
> +			}
> +		}
> +	}
> +
> +	if (handle >= DLN2_MAX_MODULES) {
> +		mutex_unlock(&dln2_modules_mutex);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	if (dln2_modules[handle].ops) {
> +		mutex_unlock(&dln2_modules_mutex);
> +		return ERR_PTR(-EBUSY);
> +	}
> +
> +	dln2_modules[handle].ops = mod_ops;
> +
> +	mutex_unlock(&dln2_modules_mutex);
> +
> +	schedule_delayed_work(&dln2_connect_work, HZ/10);
> +
> +	return &dln2_modules[handle];
> +}
> +EXPORT_SYMBOL(dln2_register_module);
> +
> +void dln2_unregister_module(struct dln2_mod *mod)
> +{
> +	mutex_lock(&dln2_modules_mutex);
> +	mod->ops = NULL;
> +	mutex_unlock(&dln2_modules_mutex);
> +}
> +EXPORT_SYMBOL(dln2_unregister_module);

I think you want to implement this driver as an MFD driver, rather than
invent your own module registration.

> +
> +static void dln2_transfer_rx_cb(struct dln2_dev *dev, struct urb *urb,
> +				struct dln2_response *rsp, void *data, int len)
> +{
> +	int handle = le16_to_cpu(rsp->hdr.handle);
> +	int rx_slot = le16_to_cpu(rsp->hdr.echo);
> +	struct dln2_rx_slots *rxs = &dev->mod_rx_slots[handle];
> +	struct dln2_rx_context *rxc;
> +
> +	spin_lock(&rxs->lock);
> +	rxc = &rxs->slots[rx_slot];
> +	if (rxc->connected) {
> +		rxc->urb = urb;
> +		complete(&rxc->done);
> +	} else {
> +		dev_dbg(&dev->interface->dev, "drop response for handle/slot %d/%d",
> +			 handle, rx_slot);
> +		usb_submit_urb(urb, GFP_ATOMIC);

Error handling? Check all usb_submit_urb calls throughout.

> +	}
> +	spin_unlock(&rxs->lock);
> +}
> +
> +static void dln2_rx(struct urb *urb)
> +{
> +	struct dln2_dev *dev = urb->context;
> +	struct dln2_response *rsp = urb->transfer_buffer;
> +	struct dln2_mod *mod;
> +	u16 id, echo, handle, size;
> +	u8 *user_data;
> +	int user_len;
> +

First of all you have to check the urb status, this could be a callback
after a failed or canceled transfer.

You also need to verify that that the received data is at least
sizeof(struct dln2_response).

> +	handle = le16_to_cpu(rsp->hdr.handle);
> +	id = le16_to_cpu(rsp->hdr.id);
> +	echo = le16_to_cpu(rsp->hdr.echo);
> +	size = le16_to_cpu(rsp->hdr.size);
> +
> +	if (handle > DLN2_MAX_MODULES)
> +		goto out_invalid_handle;
> +	mod = &dln2_modules[handle];
> +	if (!mod->ops)
> +		goto out_invalid_handle;
> +
> +	if (size != urb->actual_length)
> +		dev_warn(&dev->interface->dev, "RX len mismatch: handle %x cmd %x echo %x size %d actual %d\n",
> +			 handle, id, echo, size, urb->actual_length);
> +

Again, verify the received data length before parsing it.

> +	user_data = urb->transfer_buffer + sizeof(struct dln2_header);
> +	user_len = urb->actual_length - sizeof(struct dln2_header);
> +
> +	if (mod->ops->receive)
> +		mod->ops->receive(dev, urb, rsp, user_data, user_len);
> +	else
> +		dln2_transfer_rx_cb(dev, urb, rsp, user_data, user_len);
> +
> +	return;
> +
> +out_invalid_handle:
> +	dev_warn(&dev->interface->dev, "RX: invalid handle %d\n", handle);
> +	usb_submit_urb(urb, GFP_ATOMIC);
> +}
> +
> +static void *dln2_prep_buf(struct dln2_dev *dev, struct dln2_mod *mod, u16 cmd,
> +			   u16 echo, void *obuf, int *obuf_len, gfp_t gfp)
> +{
> +	void *buf;
> +	int len;
> +	struct dln2_header *hdr;
> +	u16 handle = dln2_get_handle(mod);
> +
> +	len = *obuf_len + sizeof(*hdr);
> +	buf = kmalloc(len, gfp);
> +	if (!buf)
> +		return NULL;
> +
> +	hdr = (struct dln2_header *)buf;
> +	hdr->id = cpu_to_le16(cmd);
> +	hdr->size = cpu_to_le16(len);
> +	hdr->echo = cpu_to_le16(echo);
> +	hdr->handle = cpu_to_le16(handle);
> +
> +	memcpy(buf + sizeof(*hdr), obuf, *obuf_len);
> +	*obuf_len = len;
> +
> +	return buf;
> +}
> +
> +static int dln2_send_wait(struct dln2_dev *dev, struct dln2_mod *mod, u16 cmd,
> +			  u16 echo, void *obuf, int obuf_len)
> +{
> +	int len = obuf_len, ret = 0, actual;
> +	void *buf;
> +
> +	if (!dev)
> +		return -ENODEV;
> +
> +	buf = dln2_prep_buf(dev, mod, cmd, echo, obuf, &len, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	ret = usb_bulk_msg(dev->usb_dev,
> +			   usb_sndbulkpipe(dev->usb_dev, dev->ep_out),
> +			   buf, len, &actual, DLN2_USB_TIMEOUT);
> +
> +	kfree(buf);
> +
> +	return ret;
> +}
> +
> +static void dln2_send_complete(struct urb *urb)
> +{
> +	kfree(urb->context);
> +	usb_free_urb(urb);
> +}
> +
> +int dln2_send(struct dln2_dev *dev, struct dln2_mod *mod, u16 cmd,
> +	      u16 echo, void *obuf, int obuf_len)
> +{
> +	int len = obuf_len, ret;

One declaration per line (here and throughout), especially if you're
initialising.

> +	struct urb *urb;
> +	void *buf;
> +
> +	if (!dev)
> +		return -ENODEV;
> +
> +	buf = dln2_prep_buf(dev, mod, cmd, echo, obuf, &len, GFP_ATOMIC);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	urb = usb_alloc_urb(0, GFP_ATOMIC);
> +	if (!urb) {
> +		kfree(buf);
> +		return -ENOMEM;
> +	}
> +
> +	usb_fill_bulk_urb(urb, dev->usb_dev,
> +			  usb_sndbulkpipe(dev->usb_dev, dev->ep_out),
> +			  buf, len, dln2_send_complete, buf);
> +
> +	ret = usb_submit_urb(urb, GFP_ATOMIC);
> +	if (ret < 0) {
> +		usb_free_urb(urb);
> +		kfree(buf);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(dln2_send);
> +
> +int dln2_transfer(struct dln2_dev *dev, struct dln2_mod *mod, u16 cmd,
> +		  void *obuf, int obuf_len, void *ibuf, int *ibuf_len)
> +{
> +	u16 result, rx_slot;
> +	struct dln2_response *rsp;
> +	int ret = 0, handle = dln2_get_handle(mod);
> +	const int timeout = DLN2_USB_TIMEOUT * HZ / 1000;
> +	struct dln2_rx_slots *rxs;
> +	struct dln2_rx_context *rxc;
> +	struct device *d;

You'd usually use dev here, and call your struct dln2_dev dln2.

> +
> +	if (!dev)
> +		return -ENODEV;
> +
> +	d = &dev->interface->dev;
> +
> +	if (mod->ops->receive) {
> +		dev_warn(&dev->interface->dev,
> +			 "module %s calls dln2_transfer w/ rx_callback set\n",
> +			 mod->ops->name);
> +		return -EINVAL;
> +	}
> +
> +	rxs = &dev->mod_rx_slots[handle];
> +
> +	rx_slot = alloc_rx_slot(rxs);
> +	if (rx_slot < 0) {
> +		dev_err(d, "alloc_rx_slot failed: %d", ret);
> +		return rx_slot;
> +	}
> +
> +	ret = dln2_send_wait(dev, mod, cmd, rx_slot, obuf, obuf_len);
> +	if (ret < 0) {
> +		free_rx_slot(rxs, rx_slot);
> +		dev_err(d, "USB write failed: %d", ret);
> +		return ret;
> +	}
> +
> +	rxc = &rxs->slots[rx_slot];
> +
> +	ret = wait_for_completion_interruptible_timeout(&rxc->done, timeout);
> +	if (ret <= 0) {
> +		ret = !ret ? -ETIMEDOUT : ret;
> +		goto out_free_rx_slot;
> +	}
> +
> +	rsp = rxc->urb->transfer_buffer;
> +	result = le16_to_cpu(rsp->result);
> +
> +	if (result) {
> +		dev_warn(d, "%d received response with error %d\n",
> +			 handle, result);
> +		ret = -EREMOTEIO;
> +		goto out_free_rx_slot;
> +	}
> +
> +	if (!ibuf) {
> +		ret = 0;
> +		goto out_free_rx_slot;
> +	}
> +
> +	if (*ibuf_len > rxc->urb->actual_length - sizeof(*rsp))
> +		*ibuf_len = rxc->urb->actual_length - sizeof(*rsp);

Again, verify that actual length is greater than the response header.

> +
> +	memcpy(ibuf, rsp + 1, *ibuf_len);
> +
> +out_free_rx_slot:
> +	free_rx_slot(rxs, rx_slot);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(dln2_transfer);
> +
> +static int dln2_check_hw(struct dln2_dev *dev)
> +{
> +	__le32 hw_type;
> +	int ret, len = sizeof(hw_type);
> +
> +
> +	ret = dln2_transfer(dev, dln2_ctrl_mod, CMD_GET_DEVICE_VER, NULL, 0,
> +			    &hw_type, &len);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (le32_to_cpu(hw_type) != DLN2_HW_ID) {
> +		dev_err(&dev->interface->dev, "Device ID 0x%x not supported!",
> +			le32_to_cpu(hw_type));
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
> +static int dln2_print_serialno(struct dln2_dev *dev)
> +{
> +	__le32 serial_no;
> +	int ret, len = sizeof(serial_no);
> +
> +
> +	ret = dln2_transfer(dev, dln2_ctrl_mod, CMD_GET_DEVICE_SN, NULL, 0,
> +			    &serial_no, &len);
> +	if (ret < 0)
> +		return ret;
> +
> +	dev_info(&dev->interface->dev,
> +		 "Diolan DLN2 device serial number is: 0x%x\n",
> +		 le32_to_cpu(serial_no));
> +
> +	return 0;
> +}
> +
> +static int dln2_hw_init(struct dln2_dev *dev)
> +{
> +	int ret;
> +
> +	dev_info(&dev->interface->dev,
> +		 "Diolan DLN2 at USB bus %03d address %03d\n",
> +		 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);

You could just drop this message, or at least drop the bus and address.
The bus is included in the dev_info message and the bus address is
readily available using lsusb should it ever be needed. 

> +
> +	ret = dln2_check_hw(dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	dln2_print_serialno(dev);
> +
> +	return ret;
> +}
> +
> +/* device layer */
> +
> +
> +static LIST_HEAD(dln2_dev_list);
> +
> +static void dln2_connect_modules(struct dln2_dev *dev)
> +{
> +	int i;
> +
> +	for (i = 0; i < DLN2_MAX_MODULES; i++)
> +		if (dln2_modules[i].ops && dln2_modules[i].ops->connect &&
> +		    !dev->mod_initialized[i] &&
> +		    !dln2_modules[i].ops->connect(dev))
> +			dev->mod_initialized[i] = true;

This is hardly readable. Add braces and inner conditionals.

> +}
> +
> +static void dln2_connect_do_work(struct work_struct *w)
> +{
> +	struct dln2_dev *dev;
> +
> +	mutex_lock(&dln2_modules_mutex);
> +	list_for_each_entry(dev, &dln2_dev_list, list)
> +		dln2_connect_modules(dev);
> +	mutex_unlock(&dln2_modules_mutex);
> +}
> +
> +static void dln2_free_rx_urbs(struct dln2_dev *dev)
> +{
> +	int i;
> +
> +	for (i = 0; i < DLN2_MAX_URBS; i++) {
> +		usb_unlink_urb(dev->rx_urb[i]);

You must use usb_kill_urb here as usb_unlink_urb is asynchronous.

> +		usb_free_urb(dev->rx_urb[i]);
> +		kfree(dev->rx_buf[i]);
> +	}
> +}
> +
> +static void dln2_free(struct dln2_dev *dev)
> +{
> +	dln2_free_rx_urbs(dev);
> +	usb_put_dev(dev->usb_dev);
> +	kfree(dev);
> +}
> +
> +static int dln2_setup_rx_urbs(struct dln2_dev *dev,
> +			      struct usb_host_interface *hostif)
> +{
> +	int i, ret;
> +	int rx_max_size = le16_to_cpu(hostif->endpoint[1].desc.wMaxPacketSize);
> +	struct device *d = &dev->interface->dev;
> +
> +	for (i = 0; i < DLN2_MAX_URBS; i++) {
> +		dev->rx_buf[i] = kmalloc(rx_max_size, GFP_KERNEL);
> +		if (!dev->rx_buf[i]) {
> +			dev_err(d, "no memory for RX buffers\n");

Drop all out-of-memory messages. This has already been logged with a
backtrace.

> +			return -ENOMEM;
> +		}
> +
> +		dev->rx_urb[i] = usb_alloc_urb(0, GFP_KERNEL);
> +		if (!dev->rx_urb[i]) {
> +			dev_err(d, "no memory for RX URBs\n");
> +			return -ENOMEM;
> +		}
> +
> +		usb_fill_bulk_urb(dev->rx_urb[i], dev->usb_dev,
> +				  usb_rcvbulkpipe(dev->usb_dev, dev->ep_in),
> +				  dev->rx_buf[i], rx_max_size, dln2_rx, dev);
> +
> +		ret = usb_submit_urb(dev->rx_urb[i], GFP_KERNEL);
> +		if (ret < 0) {
> +			dev_err(d, "failed to submit RX URB: %d\n", ret);
> +			return ret;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void dln2_disconnect(struct usb_interface *interface)
> +{
> +	struct dln2_dev *dev = usb_get_intfdata(interface);
> +	int i;
> +
> +	mutex_lock(&dln2_modules_mutex);
> +	list_del(&dev->list);
> +	for (i = 0; i < DLN2_MAX_MODULES; i++)
> +		if (dln2_modules[i].ops && dln2_modules[i].ops->disconnect &&
> +		    dev->mod_initialized[i])
> +			dln2_modules[i].ops->disconnect(dev);
> +	mutex_unlock(&dln2_modules_mutex);
> +
> +	usb_set_intfdata(interface, NULL);

This isn't needed.

You should probably set a disconnected flag though and check that in
your I/O paths to make sure that no subdriver ever triggers any I/O
after this function returns.

> +	dln2_free(dev);
> +
> +	dev_dbg(&interface->dev, "disconnected\n");
> +}
> +
> +static int dln2_probe(struct usb_interface *interface,
> +		      const struct usb_device_id *id)
> +{
> +	struct usb_host_interface *hostif = interface->cur_altsetting;
> +	struct dln2_dev *dev;
> +	int ret, i;
> +
> +	if (hostif->desc.bInterfaceNumber != 0 ||
> +	    hostif->desc.bNumEndpoints < 2)
> +		return -ENODEV;
> +
> +	/* allocate memory for our device state and initialize it */
> +	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> +	if (!dev) {
> +		dev_err(&interface->dev, "no memory for device state\n");
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +	dev->ep_out = hostif->endpoint[0].desc.bEndpointAddress;
> +	dev->ep_in = hostif->endpoint[1].desc.bEndpointAddress;
> +
> +	dev->usb_dev = usb_get_dev(interface_to_usbdev(interface));
> +	dev->interface = interface;
> +
> +	/* save our data pointer in this interface device */
> +	usb_set_intfdata(interface, dev);
> +
> +	for (i = 0; i < DLN2_MAX_MODULES; i++) {
> +		init_waitqueue_head(&dev->mod_rx_slots[i].wq);
> +		spin_lock_init(&dev->mod_rx_slots[i].lock);
> +	}
> +
> +	ret = dln2_setup_rx_urbs(dev, hostif);
> +	if (ret) {
> +		dln2_disconnect(interface);
> +		return ret;
> +	}
> +
> +	ret = dln2_hw_init(dev);
> +	if (ret < 0) {
> +		dev_err(&interface->dev, "failed to initialize hardware\n");
> +		goto out_cleanup;
> +	}
> +
> +	dev_dbg(&interface->dev, "connected " DRIVER_NAME "\n");
> +
> +	mutex_lock(&dln2_modules_mutex);
> +	dln2_connect_modules(dev);
> +	list_add(&dev->list, &dln2_dev_list);
> +	mutex_unlock(&dln2_modules_mutex);
> +
> +	return 0;
> +
> +out_cleanup:
> +	usb_set_intfdata(interface, NULL);
> +	dln2_free(dev);
> +out:
> +	return ret;
> +}
> +
> +void dln2_set_mod_context(struct dln2_mod *mod, void *context)
> +{
> +	mod->context = context;
> +}
> +EXPORT_SYMBOL(dln2_set_mod_context);
> +
> +void *dln2_get_mod_context(struct dln2_mod *mod)
> +{
> +	return mod->context;
> +}
> +EXPORT_SYMBOL(dln2_get_mod_context);

Why would you ever want these two? You don't even use them now.

> +
> +void dln2_set_dev_context(struct dln2_dev *dev, struct dln2_mod *mod,
> +			  void *context)
> +{
> +	int handle = dln2_get_handle(mod);
> +
> +	dev->context[handle] = context;
> +}
> +EXPORT_SYMBOL(dln2_set_dev_context);
> +
> +void *dln2_get_dev_context(struct dln2_dev *dev, struct dln2_mod *mod)
> +{
> +	int handle = dln2_get_handle(mod);
> +
> +	return dev->context[handle];
> +}
> +EXPORT_SYMBOL(dln2_get_dev_context);
> +
> +struct device *dln2_get_device(struct dln2_dev *dev)
> +{
> +	return &dev->interface->dev;
> +}
> +EXPORT_SYMBOL(dln2_get_device);
> +
> +static const struct usb_device_id dln2_table[] = {
> +	{ USB_DEVICE(0xa257, 0x2013) },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(usb, dln2_table);
> +
> +static struct usb_driver dln2_driver = {
> +	.name = DRIVER_NAME,
> +	.probe = dln2_probe,
> +	.disconnect = dln2_disconnect,
> +	.id_table = dln2_table,
> +};
> +
> +static struct dln2_mod_ops dln2_ctrl_mod_ops = {
> +	.name = "dln2-ctrl",
> +	.receive = NULL,
> +	.connect = NULL,
> +	.disconnect = NULL,
> +};
> +
> +static int __init dln2_init(void)
> +{
> +	int err = 0;
> +
> +	dln2_ctrl_mod = dln2_register_module(-1, &dln2_ctrl_mod_ops);

Restructure the driver as an MFD driver, and rethink the I/O interface
and you should be able to get rid of a lot of code above, including this
control module that you only use to fetch two parameters during probe.

> +
> +	if (IS_ERR(dln2_ctrl_mod)) {
> +		err = PTR_ERR(dln2_ctrl_mod);
> +		pr_err(DRIVER_NAME "dln2_register_module failed: %d\n", err);
> +		return err;
> +	}
> +
> +	err = usb_register_driver(&dln2_driver, THIS_MODULE, KBUILD_MODNAME);
> +	if (err < 0)
> +		pr_err(DRIVER_NAME "failed to register usb driver: %d\n", err);
> +
> +	return err;
> +}
> +module_init(dln2_init);
> +
> +static void __exit dln2_exit(void)
> +{
> +	usb_deregister(&dln2_driver);
> +}
> +module_exit(dln2_exit);
> +
> +MODULE_AUTHOR("Octavian Purdila <octavian.purdila@intel.com>");
> +MODULE_DESCRIPTION(DRIVER_NAME " driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/usb/dln2.h b/include/linux/usb/dln2.h
> new file mode 100644
> index 0000000..3f7f8c6
> --- /dev/null
> +++ b/include/linux/usb/dln2.h
> @@ -0,0 +1,146 @@
> +#ifndef __LINUX_USB_DLN2_H
> +#define __LINUX_USB_DLN2_H
> +
> +#include <linux/usb.h>
> +
> +struct dln2_header {
> +	__le16 size;
> +	__le16 id;
> +	__le16 echo;
> +	__le16 handle;
> +} __packed;
> +
> +struct dln2_response {
> +	struct dln2_header hdr;
> +	__le16 result;
> +} __packed;

The subdrivers should never have to worry about these details.

> +
> +
> +struct dln2_mod;
> +struct dln2_dev;
> +
> +#define DLN2_CMD(cmd, id)		((cmd) | ((id) << 8))
> +
> +/**
> + * dln2_mod_ops - DLN2 module callbacks
> + *
> + * @name - name of the module
> + *
> + * @receive - called when a message is received for the handle
> + * associated with this module. It can be NULL, and in this case
> + * dln_transfer() can be use for this module and the receive path will
> + * be handled internally. If the receive callback is used the user
> + * must call usb_sumit_urb() after finishing reading the data.

Again, handle the transport details in your core driver and let it
resubmit any urbs.

> + *
> + * @connect - called when a new DLN2 device is connected. The module
> + * should perform any needed initialization and associated the module
> + * context to this device with dln2_set_dev_context().
> + *
> + * @disconnect - called when a DLN2 device is disconnected. The module
> + * should free any resources associated with this device.
> + */
> +struct dln2_mod_ops {
> +	const char *name;
> +
> +	void (*receive)(struct dln2_dev *dev, struct urb *urb,
> +			struct dln2_response *res, void *data, int len);
> +	int (*connect)(struct dln2_dev *dev);
> +	void (*disconnect)(struct dln2_dev *dev);
> +};
> +
> +/**
> + * dl2n_register_module - register a DLN2 module
> + *
> + * @handle - the requested handle for this module that is going to be
> + * passed to the hardware; a positive value to request a specific
> + * value, or -1 to automatically allocate one
> + *
> + * @mod_ops - see dln2_mod_ops()
> + *
> + * @return an ERR_PTR is return in case of error. In case of success a
> + * dln2_mod handle is returned. The module should use
> + * dln2_set_mod_context() to associate any private context to this
> + * module.
> + */
> +struct dln2_mod *dln2_register_module(int handle, struct dln2_mod_ops *mod_ops);
> +
> +/**
> + * dl2n_register_module - unregister a DLN2 module
> + */
> +void dln2_unregister_module(struct dln2_mod *mod);
> +
> +/**
> + * dln2_transfer - issue a DLN2 command and wait for a response and
> + * the associated data
> + *
> + * Only modules that did *NOT* register a receive callback will be
> + * able to use this function.
> + *
> + * @dev - the DLN2 device on which to issue the command
> + * @mod - the DLN2 module issuing the command
> + * @cmd - the command to be sent to the device
> + * @obuf - the buffer to be sent to the device; can be NULL if the
> + * user doesn't need to transmit data with this command
> + * @obuf_len - the size of the buffer to be sent to the device
> + * @ibuf - any data associated with the response will be copied here;
> + * it can be NULL if the user doesn't need the response data
> + * @ibuf_len - must be initialized to the input buffer size; it will
> + * be modified to indicate the actual data transfered
> + *
> + * @returns 0 for success, negative value for errors
> + */
> +int dln2_transfer(struct dln2_dev *dev, struct dln2_mod *mod, u16 cmd,
> +		  void *obuf, int obuf_len, void *ibuf, int *ibuf_len);
> +
> +/**
> + * dln2_send - issue a DLN2 command without waiting for a response
> + *
> + * @dev - the DLN2 device on which to issue the command
> + * @mod - the DLN2 module issuing the command
> + * @cmd - the command to be sent to the device
> + * @echo - this value will be echoed back in the response
> + * @obuf - the buffer to be sent to the device; can be NULL if the
> + * user doesn't need to transmit data with this command
> + * @obuf_len - the size of the buffer to be sent to the device
> + *
> + * @returns 0 for success, negative value for errors
> + */
> +int dln2_send(struct dln2_dev *dev, struct dln2_mod *mod, u16 cmd, u16 echo,
> +	      void *obuf, int obuf_len);
> +
> +/**
> + * dln2_set_mod_context - store a private pointer into dln2_mod
> + *
> + * @mod - the DLN2 module
> + * @context - the private pointer to be set
> + */
> +void dln2_set_mod_context(struct dln2_mod *mod, void *context);
> +
> +/**
> + * dln2_set_mod_context - get the module private pointer from dln2_mod
> + *
> + * @mod - the DLN2 module
> + * @returns the module private pointer
> + */
> +void *dln2_get_mod_context(struct dln2_mod *mod);
> +
> +
> +/**
> + * dln2_set_mod_context - store a private pointer into dln2_dev
> + *
> + * @dev - the DLN2 device
> + * @context - the private pointer to be set
> + */
> +void dln2_set_dev_context(struct dln2_dev *dev, struct dln2_mod *mod,
> +			  void *context);
> +/**
> + * dln2_set_mod_context - get the module private pointer from dln2_dev
> + *
> + * @dev - the DLN2 device
> + * @returns the device private pointer
> + */
> +void *dln2_get_dev_context(struct dln2_dev *dev, struct dln2_mod *mod);
> +
> +struct device *dln2_get_device(struct dln2_dev *dev);
> +
> +#endif

Johan