68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
// SPDX-License-Identifier: LGPL-2.1+
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/*
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* Copyright (C) 2003 David Brownell
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*/
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/string.h>
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#include <linux/device.h>
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#include <linux/nls.h>
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#include <linux/usb/ch9.h>
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#include <linux/usb/gadget.h>
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/**
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* usb_gadget_get_string - fill out a string descriptor
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* @table: of c strings encoded using UTF-8
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* @id: string id, from low byte of wValue in get string descriptor
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* @buf: at least 256 bytes, must be 16-bit aligned
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*
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* Finds the UTF-8 string matching the ID, and converts it into a
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* string descriptor in utf16-le.
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* Returns length of descriptor (always even) or negative errno
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*
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* If your driver needs stings in multiple languages, you'll probably
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* "switch (wIndex) { ... }" in your ep0 string descriptor logic,
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* using this routine after choosing which set of UTF-8 strings to use.
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* Note that US-ASCII is a strict subset of UTF-8; any string bytes with
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* the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
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* characters (which are also widely used in C strings).
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*/
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int
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usb_gadget_get_string (const struct usb_gadget_strings *table, int id, u8 *buf)
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{
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struct usb_string *s;
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int len;
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/* descriptor 0 has the language id */
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if (id == 0) {
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buf [0] = 4;
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buf [1] = USB_DT_STRING;
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buf [2] = (u8) table->language;
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buf [3] = (u8) (table->language >> 8);
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return 4;
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}
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for (s = table->strings; s && s->s; s++)
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if (s->id == id)
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break;
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/* unrecognized: stall. */
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if (!s || !s->s)
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return -EINVAL;
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/* string descriptors have length, tag, then UTF16-LE text */
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len = min((size_t)USB_MAX_STRING_LEN, strlen(s->s));
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len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
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(wchar_t *) &buf[2], USB_MAX_STRING_LEN);
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if (len < 0)
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return -EINVAL;
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buf [0] = (len + 1) * 2;
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buf [1] = USB_DT_STRING;
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return buf [0];
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}
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EXPORT_SYMBOL_GPL(usb_gadget_get_string);
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