1// SPDX-License-Identifier: LGPL-2.1+ 2/* 3 * Copyright (C) 2003 David Brownell 4 * 5 * Ported to U-Boot by: Thomas Smits <ts.smits@gmail.com> and 6 * Remy Bohmer <linux@bohmer.net> 7 */ 8 9#include <common.h> 10#include <linux/errno.h> 11#include <linux/usb/ch9.h> 12#include <linux/usb/gadget.h> 13#include <linux/utf.h> 14 15/** 16 * usb_gadget_get_string - fill out a string descriptor 17 * @table: of c strings encoded using UTF-8 18 * @id: string id, from low byte of wValue in get string descriptor 19 * @buf: at least 256 bytes 20 * 21 * Finds the UTF-8 string matching the ID, and converts it into a 22 * string descriptor in utf16-le. 23 * Returns length of descriptor (always even) or negative errno 24 * 25 * If your driver needs stings in multiple languages, you'll probably 26 * "switch (wIndex) { ... }" in your ep0 string descriptor logic, 27 * using this routine after choosing which set of UTF-8 strings to use. 28 * Note that US-ASCII is a strict subset of UTF-8; any string bytes with 29 * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1 30 * characters (which are also widely used in C strings). 31 */ 32int 33usb_gadget_get_string(struct usb_gadget_strings *table, int id, u8 *buf) 34{ 35 struct usb_string *s; 36 int len; 37 38 if (!table) 39 return -EINVAL; 40 41 /* descriptor 0 has the language id */ 42 if (id == 0) { 43 buf[0] = 4; 44 buf[1] = USB_DT_STRING; 45 buf[2] = (u8) table->language; 46 buf[3] = (u8) (table->language >> 8); 47 return 4; 48 } 49 for (s = table->strings; s && s->s; s++) 50 if (s->id == id) 51 break; 52 53 /* unrecognized: stall. */ 54 if (!s || !s->s) 55 return -EINVAL; 56 57 /* string descriptors have length, tag, then UTF16-LE text */ 58 len = min((size_t) 126, strlen(s->s)); 59 memset(buf + 2, 0, 2 * len); /* zero all the bytes */ 60 len = utf8_to_utf16le(s->s, (__le16 *)&buf[2], len); 61 if (len < 0) 62 return -EINVAL; 63 buf[0] = (len + 1) * 2; 64 buf[1] = USB_DT_STRING; 65 return buf[0]; 66} 67