2 * usb/gadget/config.c -- simplify building config descriptors
4 * Copyright (C) 2003 David Brownell
6 * SPDX-License-Identifier: GPL-2.0+
8 * Ported to U-boot by: Thomas Smits <ts.smits@gmail.com> and
9 * Remy Bohmer <linux@bohmer.net>
13 #include <asm/errno.h>
14 #include <linux/list.h>
15 #include <linux/string.h>
17 #include <linux/usb/ch9.h>
18 #include <linux/usb/gadget.h>
22 * usb_descriptor_fillbuf - fill buffer with descriptors
23 * @buf: Buffer to be filled
24 * @buflen: Size of buf
25 * @src: Array of descriptor pointers, terminated by null pointer.
27 * Copies descriptors into the buffer, returning the length or a
28 * negative error code if they can't all be copied. Useful when
29 * assembling descriptors for an associated set of interfaces used
30 * as part of configuring a composite device; or in other cases where
31 * sets of descriptors need to be marshaled.
34 usb_descriptor_fillbuf(void *buf, unsigned buflen,
35 const struct usb_descriptor_header **src)
42 /* fill buffer from src[] until null descriptor ptr */
43 for (; NULL != *src; src++) {
44 unsigned len = (*src)->bLength;
48 memcpy(dest, *src, len);
52 return dest - (u8 *)buf;
57 * usb_gadget_config_buf - builts a complete configuration descriptor
58 * @config: Header for the descriptor, including characteristics such
59 * as power requirements and number of interfaces.
60 * @desc: Null-terminated vector of pointers to the descriptors (interface,
61 * endpoint, etc) defining all functions in this device configuration.
62 * @buf: Buffer for the resulting configuration descriptor.
63 * @length: Length of buffer. If this is not big enough to hold the
64 * entire configuration descriptor, an error code will be returned.
66 * This copies descriptors into the response buffer, building a descriptor
67 * for that configuration. It returns the buffer length or a negative
68 * status code. The config.wTotalLength field is set to match the length
69 * of the result, but other descriptor fields (including power usage and
70 * interface count) must be set by the caller.
72 * Gadget drivers could use this when constructing a config descriptor
73 * in response to USB_REQ_GET_DESCRIPTOR. They will need to patch the
74 * resulting bDescriptorType value if USB_DT_OTHER_SPEED_CONFIG is needed.
76 int usb_gadget_config_buf(
77 const struct usb_config_descriptor *config,
80 const struct usb_descriptor_header **desc
83 struct usb_config_descriptor *cp = buf;
86 /* config descriptor first */
87 if (length < USB_DT_CONFIG_SIZE || !desc)
91 /* then interface/endpoint/class/vendor/... */
92 len = usb_descriptor_fillbuf(USB_DT_CONFIG_SIZE + (u8 *)buf,
93 length - USB_DT_CONFIG_SIZE, desc);
96 len += USB_DT_CONFIG_SIZE;
100 /* patch up the config descriptor */
101 cp->bLength = USB_DT_CONFIG_SIZE;
102 cp->bDescriptorType = USB_DT_CONFIG;
103 cp->wTotalLength = cpu_to_le16(len);
104 cp->bmAttributes |= USB_CONFIG_ATT_ONE;