text: /*
   * usb/gadget/config.c -- simplify building config descriptors
   *
   * Copyright (C) 2003 David Brownell
   *
   * 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; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/list.h>
  #include <linux/string.h>
  #include <linux/device.h>
  
  #include <linux/usb/ch9.h>
  #include <linux/usb_gadget.h>
  
  
  /**
   * usb_descriptor_fillbuf - fill buffer with descriptors
   * @buf: Buffer to be filled
   * @buflen: Size of buf
   * @src: Array of descriptor pointers, terminated by null pointer.
   *
   * Copies descriptors into the buffer, returning the length or a
   * negative error code if they can't all be copied.  Useful when
   * assembling descriptors for an associated set of interfaces used
   * as part of configuring a composite device; or in other cases where
   * sets of descriptors need to be marshaled.
   */
  int
  usb_descriptor_fillbuf(void *buf, unsigned buflen,
  		const struct usb_descriptor_header **src)
  {
  	u8	*dest = buf;
  
  	if (!src)
  		return -EINVAL;
  
  	/* fill buffer from src[] until null descriptor ptr */
  	for (; 0 != *src; src++) {
  		unsigned		len = (*src)->bLength;
  
  		if (len > buflen)
  			return -EINVAL;
  		memcpy(dest, *src, len);
  		buflen -= len;
  		dest += len;
  	}
  	return dest - (u8 *)buf;
  }
  
  
  /**
   * usb_gadget_config_buf - builts a complete configuration descriptor
   * @config: Header for the descriptor, including characteristics such
   *	as power requirements and number of interfaces.
   * @desc: Null-terminated vector of pointers to the descriptors (interface,
   *	endpoint, etc) defining all functions in this device configuration.
   * @buf: Buffer for the resulting configuration descriptor.
   * @length: Length of buffer.  If this is not big enough to hold the
   *	entire configuration descriptor, an error code will be returned.
   *
   * This copies descriptors into the response buffer, building a descriptor
   * for that configuration.  It returns the buffer length or a negative
   * status code.  The config.wTotalLength field is set to match the length
   * of the result, but other descriptor fields (including power usage and
   * interface count) must be set by the caller.
   *
   * Gadget drivers could use this when constructing a config descriptor
   * in response to USB_REQ_GET_DESCRIPTOR.  They will need to patch the
   * resulting bDescriptorType value if USB_DT_OTHER_SPEED_CONFIG is needed.
   */
  int usb_gadget_config_buf(
  	const struct usb_config_descriptor	*config,
  	void					*buf,
  	unsigned				length,
  	const struct usb_descriptor_header	**desc
  )
  {
  	struct usb_config_descriptor		*cp = buf;
  	int					len;
  
  	/* config descriptor first */
  	if (length < USB_DT_CONFIG_SIZE || !desc)
  		return -EINVAL;
  	*cp = *config; 
  
  	/* then interface/endpoint/class/vendor/... */
  	len = usb_descriptor_fillbuf(USB_DT_CONFIG_SIZE + (u8*)buf,
  			length - USB_DT_CONFIG_SIZE, desc);
  	if (len < 0)
  		return len;
  	len += USB_DT_CONFIG_SIZE;
  	if (len > 0xffff)
  		return -EINVAL;
  
  	/* patch up the config descriptor */
  	cp->bLength = USB_DT_CONFIG_SIZE;
  	cp->bDescriptorType = USB_DT_CONFIG;
  	cp->wTotalLength = cpu_to_le16(len);
  	cp->bmAttributes |= USB_CONFIG_ATT_ONE;
  	return len;
  }
  
  