drivers/usb/gadget/config.c

   1 /*
   2  * usb/gadget/config.c -- simplify building config descriptors
   3  *
   4  * Copyright (C) 2003 David Brownell
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include <linux/errno.h>
  22 #include <linux/kernel.h>
  23 #include <linux/list.h>
  24 #include <linux/string.h>
  25 #include <linux/device.h>
  26
  27 #include <linux/usb_ch9.h>
  28 #include <linux/usb_gadget.h>
  29
  30
  31 /**
  32  * usb_descriptor_fillbuf - fill buffer with descriptors
  33  * @buf: Buffer to be filled
  34  * @buflen: Size of buf
  35  * @src: Array of descriptor pointers, terminated by null pointer.
  36  *
  37  * Copies descriptors into the buffer, returning the length or a
  38  * negative error code if they can't all be copied.  Useful when
  39  * assembling descriptors for an associated set of interfaces used
  40  * as part of configuring a composite device; or in other cases where
  41  * sets of descriptors need to be marshaled.
  42  */
  43 int
  44 usb_descriptor_fillbuf(void *buf, unsigned buflen,
  45                 const struct usb_descriptor_header **src)
  46 {
  47         u8      *dest = buf;
  48
  49         if (!src)
  50                 return -EINVAL;
  51
  52         /* fill buffer from src[] until null descriptor ptr */
  53         for (; 0 != *src; src++) {
  54                 unsigned                len = (*src)->bLength;
  55
  56                 if (len > buflen)
  57                         return -EINVAL;
  58                 memcpy(dest, *src, len);
  59                 buflen -= len;
  60                 dest += len;
  61         }
  62         return dest - (u8 *)buf;
  63 }
  64
  65
  66 /**
  67  * usb_gadget_config_buf - builts a complete configuration descriptor
  68  * @config: Header for the descriptor, including characteristics such
  69  *      as power requirements and number of interfaces.
  70  * @desc: Null-terminated vector of pointers to the descriptors (interface,
  71  *      endpoint, etc) defining all functions in this device configuration.
  72  * @buf: Buffer for the resulting configuration descriptor.
  73  * @length: Length of buffer.  If this is not big enough to hold the
  74  *      entire configuration descriptor, an error code will be returned.
  75  *
  76  * This copies descriptors into the response buffer, building a descriptor
  77  * for that configuration.  It returns the buffer length or a negative
  78  * status code.  The config.wTotalLength field is set to match the length
  79  * of the result, but other descriptor fields (including power usage and
  80  * interface count) must be set by the caller.
  81  *
  82  * Gadget drivers could use this when constructing a config descriptor
  83  * in response to USB_REQ_GET_DESCRIPTOR.  They will need to patch the
  84  * resulting bDescriptorType value if USB_DT_OTHER_SPEED_CONFIG is needed.
  85  */
  86 int usb_gadget_config_buf(
  87         const struct usb_config_descriptor      *config,
  88         void                                    *buf,
  89         unsigned                                length,
  90         const struct usb_descriptor_header      **desc
  91 )
  92 {
  93         struct usb_config_descriptor            *cp = buf;
  94         int                                     len;
  95
  96         /* config descriptor first */
  97         if (length < USB_DT_CONFIG_SIZE || !desc)
  98                 return -EINVAL;
  99         *cp = *config;
 100
 101         /* then interface/endpoint/class/vendor/... */
 102         len = usb_descriptor_fillbuf(USB_DT_CONFIG_SIZE + (u8*)buf,
 103                         length - USB_DT_CONFIG_SIZE, desc);
 104         if (len < 0)
 105                 return len;
 106         len += USB_DT_CONFIG_SIZE;
 107         if (len > 0xffff)
 108                 return -EINVAL;
 109
 110         /* patch up the config descriptor */
 111         cp->bLength = USB_DT_CONFIG_SIZE;
 112         cp->bDescriptorType = USB_DT_CONFIG;
 113         cp->wTotalLength = cpu_to_le16(len);
 114         cp->bmAttributes |= USB_CONFIG_ATT_ONE;
 115         return len;
 116 }
 117