text: // SPDX-License-Identifier: GPL-2.0+
  /*
   * f_hid.c -- USB HID function driver
   *
   * Copyright (C) 2010 Fabien Chouteau <fabien.chouteau@barco.com>
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/hid.h>
  #include <linux/idr.h>
  #include <linux/cdev.h>
  #include <linux/mutex.h>
  #include <linux/poll.h>
  #include <linux/uaccess.h>
  #include <linux/wait.h>
  #include <linux/sched.h>
  #include <linux/usb/g_hid.h>
  
  #include "u_f.h"
  #include "u_hid.h"
  
  #define HIDG_MINORS	4
  
  static int major, minors;
  static struct class *hidg_class;
  static DEFINE_IDA(hidg_ida);
  static DEFINE_MUTEX(hidg_ida_lock); /* protects access to hidg_ida */
  
  /*-------------------------------------------------------------------------*/
  /*                            HID gadget struct                            */
  
  struct f_hidg_req_list {
  	struct usb_request	*req;
  	unsigned int		pos;
  	struct list_head 	list;
  };
  
  struct f_hidg {
  	/* configuration */
  	unsigned char			bInterfaceSubClass;
  	unsigned char			bInterfaceProtocol;
  	unsigned char			protocol;
  	unsigned short			report_desc_length;
  	char				*report_desc;
  	unsigned short			report_length;
  
  	/* recv report */
  	struct list_head		completed_out_req;
  	spinlock_t			read_spinlock;
  	wait_queue_head_t		read_queue;
  	unsigned int			qlen;
  
  	/* send report */
  	spinlock_t			write_spinlock;
  	bool				write_pending;
  	wait_queue_head_t		write_queue;
  	struct usb_request		*req;
  
  	int				minor;
  	struct cdev			cdev;
  	struct usb_function		func;
  
  	struct usb_ep			*in_ep;
  	struct usb_ep			*out_ep;
  };
  
  static inline struct f_hidg *func_to_hidg(struct usb_function *f)
  {
  	return container_of(f, struct f_hidg, func);
  }
  
  /*-------------------------------------------------------------------------*/
  /*                           Static descriptors                            */
  
  static struct usb_interface_descriptor hidg_interface_desc = {
  	.bLength		= sizeof hidg_interface_desc,
  	.bDescriptorType	= USB_DT_INTERFACE,
  	/* .bInterfaceNumber	= DYNAMIC */
  	.bAlternateSetting	= 0,
  	.bNumEndpoints		= 2,
  	.bInterfaceClass	= USB_CLASS_HID,
  	/* .bInterfaceSubClass	= DYNAMIC */
  	/* .bInterfaceProtocol	= DYNAMIC */
  	/* .iInterface		= DYNAMIC */
  };
  
  static struct hid_descriptor hidg_desc = {
  	.bLength			= sizeof hidg_desc,
  	.bDescriptorType		= HID_DT_HID,
  	.bcdHID				= cpu_to_le16(0x0101),
  	.bCountryCode			= 0x00,
  	.bNumDescriptors		= 0x1,
  	/*.desc[0].bDescriptorType	= DYNAMIC */
  	/*.desc[0].wDescriptorLenght	= DYNAMIC */
  };
  
  /* Super-Speed Support */
  
  static struct usb_endpoint_descriptor hidg_ss_in_ep_desc = {
  	.bLength		= USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType	= USB_DT_ENDPOINT,
  	.bEndpointAddress	= USB_DIR_IN,
  	.bmAttributes		= USB_ENDPOINT_XFER_INT,
  	/*.wMaxPacketSize	= DYNAMIC */
  	.bInterval		= 4, /* FIXME: Add this field in the
  				      * HID gadget configuration?
  				      * (struct hidg_func_descriptor)
  				      */
  };
  
  static struct usb_ss_ep_comp_descriptor hidg_ss_in_comp_desc = {
  	.bLength                = sizeof(hidg_ss_in_comp_desc),
  	.bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,
  
  	/* .bMaxBurst           = 0, */
  	/* .bmAttributes        = 0, */
  	/* .wBytesPerInterval   = DYNAMIC */
  };
  
  static struct usb_endpoint_descriptor hidg_ss_out_ep_desc = {
  	.bLength		= USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType	= USB_DT_ENDPOINT,
  	.bEndpointAddress	= USB_DIR_OUT,
  	.bmAttributes		= USB_ENDPOINT_XFER_INT,
  	/*.wMaxPacketSize	= DYNAMIC */
  	.bInterval		= 4, /* FIXME: Add this field in the
  				      * HID gadget configuration?
  				      * (struct hidg_func_descriptor)
  				      */
  };
  
  static struct usb_ss_ep_comp_descriptor hidg_ss_out_comp_desc = {
  	.bLength                = sizeof(hidg_ss_out_comp_desc),
  	.bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,
  
  	/* .bMaxBurst           = 0, */
  	/* .bmAttributes        = 0, */
  	/* .wBytesPerInterval   = DYNAMIC */
  };
  
  static struct usb_descriptor_header *hidg_ss_descriptors[] = {
  	(struct usb_descriptor_header *)&hidg_interface_desc,
  	(struct usb_descriptor_header *)&hidg_desc,
  	(struct usb_descriptor_header *)&hidg_ss_in_ep_desc,
  	(struct usb_descriptor_header *)&hidg_ss_in_comp_desc,
  	(struct usb_descriptor_header *)&hidg_ss_out_ep_desc,
  	(struct usb_descriptor_header *)&hidg_ss_out_comp_desc,
  	NULL,
  };
  
  /* High-Speed Support */
  
  static struct usb_endpoint_descriptor hidg_hs_in_ep_desc = {
  	.bLength		= USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType	= USB_DT_ENDPOINT,
  	.bEndpointAddress	= USB_DIR_IN,
  	.bmAttributes		= USB_ENDPOINT_XFER_INT,
  	/*.wMaxPacketSize	= DYNAMIC */
  	.bInterval		= 4, /* FIXME: Add this field in the
  				      * HID gadget configuration?
  				      * (struct hidg_func_descriptor)
  				      */
  };
  
  static struct usb_endpoint_descriptor hidg_hs_out_ep_desc = {
  	.bLength		= USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType	= USB_DT_ENDPOINT,
  	.bEndpointAddress	= USB_DIR_OUT,
  	.bmAttributes		= USB_ENDPOINT_XFER_INT,
  	/*.wMaxPacketSize	= DYNAMIC */
  	.bInterval		= 4, /* FIXME: Add this field in the
  				      * HID gadget configuration?
  				      * (struct hidg_func_descriptor)
  				      */
  };
  
  static struct usb_descriptor_header *hidg_hs_descriptors[] = {
  	(struct usb_descriptor_header *)&hidg_interface_desc,
  	(struct usb_descriptor_header *)&hidg_desc,
  	(struct usb_descriptor_header *)&hidg_hs_in_ep_desc,
  	(struct usb_descriptor_header *)&hidg_hs_out_ep_desc,
  	NULL,
  };
  
  /* Full-Speed Support */
  
  static struct usb_endpoint_descriptor hidg_fs_in_ep_desc = {
  	.bLength		= USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType	= USB_DT_ENDPOINT,
  	.bEndpointAddress	= USB_DIR_IN,
  	.bmAttributes		= USB_ENDPOINT_XFER_INT,
  	/*.wMaxPacketSize	= DYNAMIC */
  	.bInterval		= 10, /* FIXME: Add this field in the
  				       * HID gadget configuration?
  				       * (struct hidg_func_descriptor)
  				       */
  };
  
  static struct usb_endpoint_descriptor hidg_fs_out_ep_desc = {
  	.bLength		= USB_DT_ENDPOINT_SIZE,
  	.bDescriptorType	= USB_DT_ENDPOINT,
  	.bEndpointAddress	= USB_DIR_OUT,
  	.bmAttributes		= USB_ENDPOINT_XFER_INT,
  	/*.wMaxPacketSize	= DYNAMIC */
  	.bInterval		= 10, /* FIXME: Add this field in the
  				       * HID gadget configuration?
  				       * (struct hidg_func_descriptor)
  				       */
  };
  
  static struct usb_descriptor_header *hidg_fs_descriptors[] = {
  	(struct usb_descriptor_header *)&hidg_interface_desc,
  	(struct usb_descriptor_header *)&hidg_desc,
  	(struct usb_descriptor_header *)&hidg_fs_in_ep_desc,
  	(struct usb_descriptor_header *)&hidg_fs_out_ep_desc,
  	NULL,
  };
  
  /*-------------------------------------------------------------------------*/
  /*                                 Strings                                 */
  
  #define CT_FUNC_HID_IDX	0
  
  static struct usb_string ct_func_string_defs[] = {
  	[CT_FUNC_HID_IDX].s	= "HID Interface",
  	{},			/* end of list */
  };
  
  static struct usb_gadget_strings ct_func_string_table = {
  	.language	= 0x0409,	/* en-US */
  	.strings	= ct_func_string_defs,
  };
  
  static struct usb_gadget_strings *ct_func_strings[] = {
  	&ct_func_string_table,
  	NULL,
  };
  
  /*-------------------------------------------------------------------------*/
  /*                              Char Device                                */
  
  static ssize_t f_hidg_read(struct file *file, char __user *buffer,
  			size_t count, loff_t *ptr)
  {
  	struct f_hidg *hidg = file->private_data;
  	struct f_hidg_req_list *list;
  	struct usb_request *req;
  	unsigned long flags;
  	int ret;
  
  	if (!count)
  		return 0;
  
  	spin_lock_irqsave(&hidg->read_spinlock, flags);
  
  #define READ_COND (!list_empty(&hidg->completed_out_req))
  
  	/* wait for at least one buffer to complete */
  	while (!READ_COND) {
  		spin_unlock_irqrestore(&hidg->read_spinlock, flags);
  		if (file->f_flags & O_NONBLOCK)
  			return -EAGAIN;
  
  		if (wait_event_interruptible(hidg->read_queue, READ_COND))
  			return -ERESTARTSYS;
  
  		spin_lock_irqsave(&hidg->read_spinlock, flags);
  	}
  
  	/* pick the first one */
  	list = list_first_entry(&hidg->completed_out_req,
  				struct f_hidg_req_list, list);
  
  	/*
  	 * Remove this from list to protect it from beign free()
  	 * while host disables our function
  	 */
  	list_del(&list->list);
  
  	req = list->req;
  	count = min_t(unsigned int, count, req->actual - list->pos);
  	spin_unlock_irqrestore(&hidg->read_spinlock, flags);
  
  	/* copy to user outside spinlock */
  	count -= copy_to_user(buffer, req->buf + list->pos, count);
  	list->pos += count;
  
  	/*
  	 * if this request is completely handled and transfered to
  	 * userspace, remove its entry from the list and requeue it
  	 * again. Otherwise, we will revisit it again upon the next
  	 * call, taking into account its current read position.
  	 */
  	if (list->pos == req->actual) {
  		kfree(list);
  
  		req->length = hidg->report_length;
  		ret = usb_ep_queue(hidg->out_ep, req, GFP_KERNEL);
  		if (ret < 0) {
  			free_ep_req(hidg->out_ep, req);
  			return ret;
  		}
  	} else {
  		spin_lock_irqsave(&hidg->read_spinlock, flags);
  		list_add(&list->list, &hidg->completed_out_req);
  		spin_unlock_irqrestore(&hidg->read_spinlock, flags);
  
  		wake_up(&hidg->read_queue);
  	}
  
  	return count;
  }
  
  static void f_hidg_req_complete(struct usb_ep *ep, struct usb_request *req)
  {
  	struct f_hidg *hidg = (struct f_hidg *)ep->driver_data;
  	unsigned long flags;
  
  	if (req->status != 0) {
  		ERROR(hidg->func.config->cdev,
  			"End Point Request ERROR: %d\n", req->status);
  	}
  
  	spin_lock_irqsave(&hidg->write_spinlock, flags);
  	hidg->write_pending = 0;
  	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
  	wake_up(&hidg->write_queue);
  }
  
  static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
  			    size_t count, loff_t *offp)
  {
  	struct f_hidg *hidg  = file->private_data;
  	struct usb_request *req;
  	unsigned long flags;
  	ssize_t status = -ENOMEM;
  
  	spin_lock_irqsave(&hidg->write_spinlock, flags);
  
  #define WRITE_COND (!hidg->write_pending)
  try_again:
  	/* write queue */
  	while (!WRITE_COND) {
  		spin_unlock_irqrestore(&hidg->write_spinlock, flags);
  		if (file->f_flags & O_NONBLOCK)
  			return -EAGAIN;
  
  		if (wait_event_interruptible_exclusive(
  				hidg->write_queue, WRITE_COND))
  			return -ERESTARTSYS;
  
  		spin_lock_irqsave(&hidg->write_spinlock, flags);
  	}
  
  	hidg->write_pending = 1;
  	req = hidg->req;
  	count  = min_t(unsigned, count, hidg->report_length);
  
  	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
  	status = copy_from_user(req->buf, buffer, count);
  
  	if (status != 0) {
  		ERROR(hidg->func.config->cdev,
  			"copy_from_user error\n");
  		status = -EINVAL;
  		goto release_write_pending;
  	}
  
  	spin_lock_irqsave(&hidg->write_spinlock, flags);
  
  	/* when our function has been disabled by host */
  	if (!hidg->req) {
  		free_ep_req(hidg->in_ep, req);
  		/*
  		 * TODO
  		 * Should we fail with error here?
  		 */
  		goto try_again;
  	}
  
  	req->status   = 0;
  	req->zero     = 0;
  	req->length   = count;
  	req->complete = f_hidg_req_complete;
  	req->context  = hidg;
  
  	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
  
  	status = usb_ep_queue(hidg->in_ep, req, GFP_ATOMIC);
  	if (status < 0) {
  		ERROR(hidg->func.config->cdev,
  			"usb_ep_queue error on int endpoint %zd\n", status);
  		goto release_write_pending;
  	} else {
  		status = count;
  	}
  
  	return status;
  release_write_pending:
  	spin_lock_irqsave(&hidg->write_spinlock, flags);
  	hidg->write_pending = 0;
  	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
  
  	wake_up(&hidg->write_queue);
  
  	return status;
  }
  
  static __poll_t f_hidg_poll(struct file *file, poll_table *wait)
  {
  	struct f_hidg	*hidg  = file->private_data;
  	__poll_t	ret = 0;
  
  	poll_wait(file, &hidg->read_queue, wait);
  	poll_wait(file, &hidg->write_queue, wait);
  
  	if (WRITE_COND)
  		ret |= EPOLLOUT | EPOLLWRNORM;
  
  	if (READ_COND)
  		ret |= EPOLLIN | EPOLLRDNORM;
  
  	return ret;
  }
  
  #undef WRITE_COND
  #undef READ_COND
  
  static int f_hidg_release(struct inode *inode, struct file *fd)
  {
  	fd->private_data = NULL;
  	return 0;
  }
  
  static int f_hidg_open(struct inode *inode, struct file *fd)
  {
  	struct f_hidg *hidg =
  		container_of(inode->i_cdev, struct f_hidg, cdev);
  
  	fd->private_data = hidg;
  
  	return 0;
  }
  
  /*-------------------------------------------------------------------------*/
  /*                                usb_function                             */
  
  static inline struct usb_request *hidg_alloc_ep_req(struct usb_ep *ep,
  						    unsigned length)
  {
  	return alloc_ep_req(ep, length);
  }
  
  static void hidg_set_report_complete(struct usb_ep *ep, struct usb_request *req)
  {
  	struct f_hidg *hidg = (struct f_hidg *) req->context;
  	struct usb_composite_dev *cdev = hidg->func.config->cdev;
  	struct f_hidg_req_list *req_list;
  	unsigned long flags;
  
  	switch (req->status) {
  	case 0:
  		req_list = kzalloc(sizeof(*req_list), GFP_ATOMIC);
  		if (!req_list) {
  			ERROR(cdev, "Unable to allocate mem for req_list\n");
  			goto free_req;
  		}
  
  		req_list->req = req;
  
  		spin_lock_irqsave(&hidg->read_spinlock, flags);
  		list_add_tail(&req_list->list, &hidg->completed_out_req);
  		spin_unlock_irqrestore(&hidg->read_spinlock, flags);
  
  		wake_up(&hidg->read_queue);
  		break;
  	default:
  		ERROR(cdev, "Set report failed %d\n", req->status);
  		fallthrough;
  	case -ECONNABORTED:		/* hardware forced ep reset */
  	case -ECONNRESET:		/* request dequeued */
  	case -ESHUTDOWN:		/* disconnect from host */
  free_req:
  		free_ep_req(ep, req);
  		return;
  	}
  }
  
  static int hidg_setup(struct usb_function *f,
  		const struct usb_ctrlrequest *ctrl)
  {
  	struct f_hidg			*hidg = func_to_hidg(f);
  	struct usb_composite_dev	*cdev = f->config->cdev;
  	struct usb_request		*req  = cdev->req;
  	int status = 0;
  	__u16 value, length;
  
  	value	= __le16_to_cpu(ctrl->wValue);
  	length	= __le16_to_cpu(ctrl->wLength);
  
  	VDBG(cdev,
  	     "%s crtl_request : bRequestType:0x%x bRequest:0x%x Value:0x%x\n",
  	     __func__, ctrl->bRequestType, ctrl->bRequest, value);
  
  	switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
  	case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
  		  | HID_REQ_GET_REPORT):
  		VDBG(cdev, "get_report\n");
  
  		/* send an empty report */
  		length = min_t(unsigned, length, hidg->report_length);
  		memset(req->buf, 0x0, length);
  
  		goto respond;
  		break;
  
  	case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
  		  | HID_REQ_GET_PROTOCOL):
  		VDBG(cdev, "get_protocol\n");
  		length = min_t(unsigned int, length, 1);
  		((u8 *) req->buf)[0] = hidg->protocol;
  		goto respond;
  		break;
  
  	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
  		  | HID_REQ_SET_REPORT):
  		VDBG(cdev, "set_report | wLength=%d\n", ctrl->wLength);
  		goto stall;
  		break;
  
  	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
  		  | HID_REQ_SET_PROTOCOL):
  		VDBG(cdev, "set_protocol\n");
  		if (value > HID_REPORT_PROTOCOL)
  			goto stall;
  		length = 0;
  		/*
  		 * We assume that programs implementing the Boot protocol
  		 * are also compatible with the Report Protocol
  		 */
  		if (hidg->bInterfaceSubClass == USB_INTERFACE_SUBCLASS_BOOT) {
  			hidg->protocol = value;
  			goto respond;
  		}
  		goto stall;
  		break;
  
  	case ((USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_INTERFACE) << 8
  		  | USB_REQ_GET_DESCRIPTOR):
  		switch (value >> 8) {
  		case HID_DT_HID:
  		{
  			struct hid_descriptor hidg_desc_copy = hidg_desc;
  
  			VDBG(cdev, "USB_REQ_GET_DESCRIPTOR: HID\n");
  			hidg_desc_copy.desc[0].bDescriptorType = HID_DT_REPORT;
  			hidg_desc_copy.desc[0].wDescriptorLength =
  				cpu_to_le16(hidg->report_desc_length);
  
  			length = min_t(unsigned short, length,
  						   hidg_desc_copy.bLength);
  			memcpy(req->buf, &hidg_desc_copy, length);
  			goto respond;
  			break;
  		}
  		case HID_DT_REPORT:
  			VDBG(cdev, "USB_REQ_GET_DESCRIPTOR: REPORT\n");
  			length = min_t(unsigned short, length,
  						   hidg->report_desc_length);
  			memcpy(req->buf, hidg->report_desc, length);
  			goto respond;
  			break;
  
  		default:
  			VDBG(cdev, "Unknown descriptor request 0x%x\n",
  				 value >> 8);
  			goto stall;
  			break;
  		}
  		break;
  
  	default:
  		VDBG(cdev, "Unknown request 0x%x\n",
  			 ctrl->bRequest);
  		goto stall;
  		break;
  	}
  
  stall:
  	return -EOPNOTSUPP;
  
  respond:
  	req->zero = 0;
  	req->length = length;
  	status = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
  	if (status < 0)
  		ERROR(cdev, "usb_ep_queue error on ep0 %d\n", value);
  	return status;
  }
  
  static void hidg_disable(struct usb_function *f)
  {
  	struct f_hidg *hidg = func_to_hidg(f);
  	struct f_hidg_req_list *list, *next;
  	unsigned long flags;
  
  	usb_ep_disable(hidg->in_ep);
  	usb_ep_disable(hidg->out_ep);
  
  	spin_lock_irqsave(&hidg->read_spinlock, flags);
  	list_for_each_entry_safe(list, next, &hidg->completed_out_req, list) {
  		free_ep_req(hidg->out_ep, list->req);
  		list_del(&list->list);
  		kfree(list);
  	}
  	spin_unlock_irqrestore(&hidg->read_spinlock, flags);
  
  	spin_lock_irqsave(&hidg->write_spinlock, flags);
  	if (!hidg->write_pending) {
  		free_ep_req(hidg->in_ep, hidg->req);
  		hidg->write_pending = 1;
  	}
  
  	hidg->req = NULL;
  	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
  }
  
  static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
  {
  	struct usb_composite_dev		*cdev = f->config->cdev;
  	struct f_hidg				*hidg = func_to_hidg(f);
  	struct usb_request			*req_in = NULL;
  	unsigned long				flags;
  	int i, status = 0;
  
  	VDBG(cdev, "hidg_set_alt intf:%d alt:%d\n", intf, alt);
  
  	if (hidg->in_ep != NULL) {
  		/* restart endpoint */
  		usb_ep_disable(hidg->in_ep);
  
  		status = config_ep_by_speed(f->config->cdev->gadget, f,
  					    hidg->in_ep);
  		if (status) {
  			ERROR(cdev, "config_ep_by_speed FAILED!\n");
  			goto fail;
  		}
  		status = usb_ep_enable(hidg->in_ep);
  		if (status < 0) {
  			ERROR(cdev, "Enable IN endpoint FAILED!\n");
  			goto fail;
  		}
  		hidg->in_ep->driver_data = hidg;
  
  		req_in = hidg_alloc_ep_req(hidg->in_ep, hidg->report_length);
  		if (!req_in) {
  			status = -ENOMEM;
  			goto disable_ep_in;
  		}
  	}
  
  
  	if (hidg->out_ep != NULL) {
  		/* restart endpoint */
  		usb_ep_disable(hidg->out_ep);
  
  		status = config_ep_by_speed(f->config->cdev->gadget, f,
  					    hidg->out_ep);
  		if (status) {
  			ERROR(cdev, "config_ep_by_speed FAILED!\n");
  			goto free_req_in;
  		}
  		status = usb_ep_enable(hidg->out_ep);
  		if (status < 0) {
  			ERROR(cdev, "Enable OUT endpoint FAILED!\n");
  			goto free_req_in;
  		}
  		hidg->out_ep->driver_data = hidg;
  
  		/*
  		 * allocate a bunch of read buffers and queue them all at once.
  		 */
  		for (i = 0; i < hidg->qlen && status == 0; i++) {
  			struct usb_request *req =
  					hidg_alloc_ep_req(hidg->out_ep,
  							  hidg->report_length);
  			if (req) {
  				req->complete = hidg_set_report_complete;
  				req->context  = hidg;
  				status = usb_ep_queue(hidg->out_ep, req,
  						      GFP_ATOMIC);
  				if (status) {
  					ERROR(cdev, "%s queue req --> %d\n",
  						hidg->out_ep->name, status);
  					free_ep_req(hidg->out_ep, req);
  				}
  			} else {
  				status = -ENOMEM;
  				goto disable_out_ep;
  			}
  		}
  	}
  
  	if (hidg->in_ep != NULL) {
  		spin_lock_irqsave(&hidg->write_spinlock, flags);
  		hidg->req = req_in;
  		hidg->write_pending = 0;
  		spin_unlock_irqrestore(&hidg->write_spinlock, flags);
  
  		wake_up(&hidg->write_queue);
  	}
  	return 0;
  disable_out_ep:
  	usb_ep_disable(hidg->out_ep);
  free_req_in:
  	if (req_in)
  		free_ep_req(hidg->in_ep, req_in);
  
  disable_ep_in:
  	if (hidg->in_ep)
  		usb_ep_disable(hidg->in_ep);
  
  fail:
  	return status;
  }
  
  static const struct file_operations f_hidg_fops = {
  	.owner		= THIS_MODULE,
  	.open		= f_hidg_open,
  	.release	= f_hidg_release,
  	.write		= f_hidg_write,
  	.read		= f_hidg_read,
  	.poll		= f_hidg_poll,
  	.llseek		= noop_llseek,
  };
  
  static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
  {
  	struct usb_ep		*ep;
  	struct f_hidg		*hidg = func_to_hidg(f);
  	struct usb_string	*us;
  	struct device		*device;
  	int			status;
  	dev_t			dev;
  
  	/* maybe allocate device-global string IDs, and patch descriptors */
  	us = usb_gstrings_attach(c->cdev, ct_func_strings,
  				 ARRAY_SIZE(ct_func_string_defs));
  	if (IS_ERR(us))
  		return PTR_ERR(us);
  	hidg_interface_desc.iInterface = us[CT_FUNC_HID_IDX].id;
  
  	/* allocate instance-specific interface IDs, and patch descriptors */
  	status = usb_interface_id(c, f);
  	if (status < 0)
  		goto fail;
  	hidg_interface_desc.bInterfaceNumber = status;
  
  	/* allocate instance-specific endpoints */
  	status = -ENODEV;
  	ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_in_ep_desc);
  	if (!ep)
  		goto fail;
  	hidg->in_ep = ep;
  
  	ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_out_ep_desc);
  	if (!ep)
  		goto fail;
  	hidg->out_ep = ep;
  
  	/* set descriptor dynamic values */
  	hidg_interface_desc.bInterfaceSubClass = hidg->bInterfaceSubClass;
  	hidg_interface_desc.bInterfaceProtocol = hidg->bInterfaceProtocol;
  	hidg->protocol = HID_REPORT_PROTOCOL;
  	hidg_ss_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
  	hidg_ss_in_comp_desc.wBytesPerInterval =
  				cpu_to_le16(hidg->report_length);
  	hidg_hs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
  	hidg_fs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
  	hidg_ss_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
  	hidg_ss_out_comp_desc.wBytesPerInterval =
  				cpu_to_le16(hidg->report_length);
  	hidg_hs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
  	hidg_fs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
  	/*
  	 * We can use hidg_desc struct here but we should not relay
  	 * that its content won't change after returning from this function.
  	 */
  	hidg_desc.desc[0].bDescriptorType = HID_DT_REPORT;
  	hidg_desc.desc[0].wDescriptorLength =
  		cpu_to_le16(hidg->report_desc_length);
  
  	hidg_hs_in_ep_desc.bEndpointAddress =
  		hidg_fs_in_ep_desc.bEndpointAddress;
  	hidg_hs_out_ep_desc.bEndpointAddress =
  		hidg_fs_out_ep_desc.bEndpointAddress;
  
  	hidg_ss_in_ep_desc.bEndpointAddress =
  		hidg_fs_in_ep_desc.bEndpointAddress;
  	hidg_ss_out_ep_desc.bEndpointAddress =
  		hidg_fs_out_ep_desc.bEndpointAddress;
  
  	status = usb_assign_descriptors(f, hidg_fs_descriptors,
  			hidg_hs_descriptors, hidg_ss_descriptors,
  			hidg_ss_descriptors);
  	if (status)
  		goto fail;
  
  	spin_lock_init(&hidg->write_spinlock);
  	hidg->write_pending = 1;
  	hidg->req = NULL;
  	spin_lock_init(&hidg->read_spinlock);
  	init_waitqueue_head(&hidg->write_queue);
  	init_waitqueue_head(&hidg->read_queue);
  	INIT_LIST_HEAD(&hidg->completed_out_req);
  
  	/* create char device */
  	cdev_init(&hidg->cdev, &f_hidg_fops);
  	dev = MKDEV(major, hidg->minor);
  	status = cdev_add(&hidg->cdev, dev, 1);
  	if (status)
  		goto fail_free_descs;
  
  	device = device_create(hidg_class, NULL, dev, NULL,
  			       "%s%d", "hidg", hidg->minor);
  	if (IS_ERR(device)) {
  		status = PTR_ERR(device);
  		goto del;
  	}
  
  	return 0;
  del:
  	cdev_del(&hidg->cdev);
  fail_free_descs:
  	usb_free_all_descriptors(f);
  fail:
  	ERROR(f->config->cdev, "hidg_bind FAILED\n");
  	if (hidg->req != NULL)
  		free_ep_req(hidg->in_ep, hidg->req);
  
  	return status;
  }
  
  static inline int hidg_get_minor(void)
  {
  	int ret;
  
  	ret = ida_simple_get(&hidg_ida, 0, 0, GFP_KERNEL);
  	if (ret >= HIDG_MINORS) {
  		ida_simple_remove(&hidg_ida, ret);
  		ret = -ENODEV;
  	}
  
  	return ret;
  }
  
  static inline struct f_hid_opts *to_f_hid_opts(struct config_item *item)
  {
  	return container_of(to_config_group(item), struct f_hid_opts,
  			    func_inst.group);
  }
  
  static void hid_attr_release(struct config_item *item)
  {
  	struct f_hid_opts *opts = to_f_hid_opts(item);
  
  	usb_put_function_instance(&opts->func_inst);
  }
  
  static struct configfs_item_operations hidg_item_ops = {
  	.release	= hid_attr_release,
  };
  
  #define F_HID_OPT(name, prec, limit)					\
  static ssize_t f_hid_opts_##name##_show(struct config_item *item, char *page)\
  {									\
  	struct f_hid_opts *opts = to_f_hid_opts(item);			\
  	int result;							\
  									\
  	mutex_lock(&opts->lock);					\
  	result = sprintf(page, "%d\n", opts->name);			\
  	mutex_unlock(&opts->lock);					\
  									\
  	return result;							\
  }									\
  									\
  static ssize_t f_hid_opts_##name##_store(struct config_item *item,	\
  					 const char *page, size_t len)	\
  {									\
  	struct f_hid_opts *opts = to_f_hid_opts(item);			\
  	int ret;							\
  	u##prec num;							\
  									\
  	mutex_lock(&opts->lock);					\
  	if (opts->refcnt) {						\
  		ret = -EBUSY;						\
  		goto end;						\
  	}								\
  									\
  	ret = kstrtou##prec(page, 0, &num);				\
  	if (ret)							\
  		goto end;						\
  									\
  	if (num > limit) {						\
  		ret = -EINVAL;						\
  		goto end;						\
  	}								\
  	opts->name = num;						\
  	ret = len;							\
  									\
  end:									\
  	mutex_unlock(&opts->lock);					\
  	return ret;							\
  }									\
  									\
  CONFIGFS_ATTR(f_hid_opts_, name)
  
  F_HID_OPT(subclass, 8, 255);
  F_HID_OPT(protocol, 8, 255);
  F_HID_OPT(report_length, 16, 65535);
  
  static ssize_t f_hid_opts_report_desc_show(struct config_item *item, char *page)
  {
  	struct f_hid_opts *opts = to_f_hid_opts(item);
  	int result;
  
  	mutex_lock(&opts->lock);
  	result = opts->report_desc_length;
  	memcpy(page, opts->report_desc, opts->report_desc_length);
  	mutex_unlock(&opts->lock);
  
  	return result;
  }
  
  static ssize_t f_hid_opts_report_desc_store(struct config_item *item,
  					    const char *page, size_t len)
  {
  	struct f_hid_opts *opts = to_f_hid_opts(item);
  	int ret = -EBUSY;
  	char *d;
  
  	mutex_lock(&opts->lock);
  
  	if (opts->refcnt)
  		goto end;
  	if (len > PAGE_SIZE) {
  		ret = -ENOSPC;
  		goto end;
  	}
  	d = kmemdup(page, len, GFP_KERNEL);
  	if (!d) {
  		ret = -ENOMEM;
  		goto end;
  	}
  	kfree(opts->report_desc);
  	opts->report_desc = d;
  	opts->report_desc_length = len;
  	opts->report_desc_alloc = true;
  	ret = len;
  end:
  	mutex_unlock(&opts->lock);
  	return ret;
  }
  
  CONFIGFS_ATTR(f_hid_opts_, report_desc);
  
  static ssize_t f_hid_opts_dev_show(struct config_item *item, char *page)
  {
  	struct f_hid_opts *opts = to_f_hid_opts(item);
  
  	return sprintf(page, "%d:%d\n", major, opts->minor);
  }
  
  CONFIGFS_ATTR_RO(f_hid_opts_, dev);
  
  static struct configfs_attribute *hid_attrs[] = {
  	&f_hid_opts_attr_subclass,
  	&f_hid_opts_attr_protocol,
  	&f_hid_opts_attr_report_length,
  	&f_hid_opts_attr_report_desc,
  	&f_hid_opts_attr_dev,
  	NULL,
  };
  
  static const struct config_item_type hid_func_type = {
  	.ct_item_ops	= &hidg_item_ops,
  	.ct_attrs	= hid_attrs,
  	.ct_owner	= THIS_MODULE,
  };
  
  static inline void hidg_put_minor(int minor)
  {
  	ida_simple_remove(&hidg_ida, minor);
  }
  
  static void hidg_free_inst(struct usb_function_instance *f)
  {
  	struct f_hid_opts *opts;
  
  	opts = container_of(f, struct f_hid_opts, func_inst);
  
  	mutex_lock(&hidg_ida_lock);
  
  	hidg_put_minor(opts->minor);
  	if (ida_is_empty(&hidg_ida))
  		ghid_cleanup();
  
  	mutex_unlock(&hidg_ida_lock);
  
  	if (opts->report_desc_alloc)
  		kfree(opts->report_desc);
  
  	kfree(opts);
  }
  
  static struct usb_function_instance *hidg_alloc_inst(void)
  {
  	struct f_hid_opts *opts;
  	struct usb_function_instance *ret;
  	int status = 0;
  
  	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
  	if (!opts)
  		return ERR_PTR(-ENOMEM);
  	mutex_init(&opts->lock);
  	opts->func_inst.free_func_inst = hidg_free_inst;
  	ret = &opts->func_inst;
  
  	mutex_lock(&hidg_ida_lock);
  
  	if (ida_is_empty(&hidg_ida)) {
  		status = ghid_setup(NULL, HIDG_MINORS);
  		if (status)  {
  			ret = ERR_PTR(status);
  			kfree(opts);
  			goto unlock;
  		}
  	}
  
  	opts->minor = hidg_get_minor();
  	if (opts->minor < 0) {
  		ret = ERR_PTR(opts->minor);
  		kfree(opts);
  		if (ida_is_empty(&hidg_ida))
  			ghid_cleanup();
  		goto unlock;
  	}
  	config_group_init_type_name(&opts->func_inst.group, "", &hid_func_type);
  
  unlock:
  	mutex_unlock(&hidg_ida_lock);
  	return ret;
  }
  
  static void hidg_free(struct usb_function *f)
  {
  	struct f_hidg *hidg;
  	struct f_hid_opts *opts;
  
  	hidg = func_to_hidg(f);
  	opts = container_of(f->fi, struct f_hid_opts, func_inst);
  	kfree(hidg->report_desc);
  	kfree(hidg);
  	mutex_lock(&opts->lock);
  	--opts->refcnt;
  	mutex_unlock(&opts->lock);
  }
  
  static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
  {
  	struct f_hidg *hidg = func_to_hidg(f);
  
  	device_destroy(hidg_class, MKDEV(major, hidg->minor));
  	cdev_del(&hidg->cdev);
  
  	usb_free_all_descriptors(f);
  }
  
  static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
  {
  	struct f_hidg *hidg;
  	struct f_hid_opts *opts;
  
  	/* allocate and initialize one new instance */
  	hidg = kzalloc(sizeof(*hidg), GFP_KERNEL);
  	if (!hidg)
  		return ERR_PTR(-ENOMEM);
  
  	opts = container_of(fi, struct f_hid_opts, func_inst);
  
  	mutex_lock(&opts->lock);
  	++opts->refcnt;
  
  	hidg->minor = opts->minor;
  	hidg->bInterfaceSubClass = opts->subclass;
  	hidg->bInterfaceProtocol = opts->protocol;
  	hidg->report_length = opts->report_length;
  	hidg->report_desc_length = opts->report_desc_length;
  	if (opts->report_desc) {
  		hidg->report_desc = kmemdup(opts->report_desc,
  					    opts->report_desc_length,
  					    GFP_KERNEL);
  		if (!hidg->report_desc) {
  			kfree(hidg);
  			mutex_unlock(&opts->lock);
  			return ERR_PTR(-ENOMEM);
  		}
  	}
  
  	mutex_unlock(&opts->lock);
  
  	hidg->func.name    = "hid";
  	hidg->func.bind    = hidg_bind;
  	hidg->func.unbind  = hidg_unbind;
  	hidg->func.set_alt = hidg_set_alt;
  	hidg->func.disable = hidg_disable;
  	hidg->func.setup   = hidg_setup;
  	hidg->func.free_func = hidg_free;
  
  	/* this could me made configurable at some point */
  	hidg->qlen	   = 4;
  
  	return &hidg->func;
  }
  
  DECLARE_USB_FUNCTION_INIT(hid, hidg_alloc_inst, hidg_alloc);
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Fabien Chouteau");
  
  int ghid_setup(struct usb_gadget *g, int count)
  {
  	int status;
  	dev_t dev;
  
  	hidg_class = class_create(THIS_MODULE, "hidg");
  	if (IS_ERR(hidg_class)) {
  		status = PTR_ERR(hidg_class);
  		hidg_class = NULL;
  		return status;
  	}
  
  	status = alloc_chrdev_region(&dev, 0, count, "hidg");
  	if (status) {
  		class_destroy(hidg_class);
  		hidg_class = NULL;
  		return status;
  	}
  
  	major = MAJOR(dev);
  	minors = count;
  
  	return 0;
  }
  
  void ghid_cleanup(void)
  {
  	if (major) {
  		unregister_chrdev_region(MKDEV(major, 0), minors);
  		major = minors = 0;
  	}
  
  	class_destroy(hidg_class);
  	hidg_class = NULL;
  }
  