1 files changed, 136 insertions, 0 deletions
diff --git a/drivers/usb/gadget/usbstring.c b/drivers/usb/gadget/usbstring.c
new file mode 100644
index 000000000000..b1735767660b
--- /dev/null
+++ b/drivers/usb/gadget/usbstring.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2003 David Brownell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/string.h>
+#include <linux/device.h>
+#include <linux/init.h>
+
+#include <linux/usb_ch9.h>
+#include <linux/usb_gadget.h>
+
+#include <asm/unaligned.h>
+
+
+static int utf8_to_utf16le(const char *s, __le16 *cp, unsigned len)
+{
+	int	count = 0;
+	u8	c;
+	u16	uchar;
+
+	/* this insists on correct encodings, though not minimal ones.
+	 * BUT it currently rejects legit 4-byte UTF-8 code points,
+	 * which need surrogate pairs.  (Unicode 3.1 can use them.)
+	 */
+	while (len != 0 && (c = (u8) *s++) != 0) {
+		if (unlikely(c & 0x80)) {
+			// 2-byte sequence:
+			// 00000yyyyyxxxxxx = 110yyyyy 10xxxxxx
+			if ((c & 0xe0) == 0xc0) {
+				uchar = (c & 0x1f) << 6;
+
+				c = (u8) *s++;
+				if ((c & 0xc0) != 0xc0)
+					goto fail;
+				c &= 0x3f;
+				uchar |= c;
+
+			// 3-byte sequence (most CJKV characters):
+			// zzzzyyyyyyxxxxxx = 1110zzzz 10yyyyyy 10xxxxxx
+			} else if ((c & 0xf0) == 0xe0) {
+				uchar = (c & 0x0f) << 12;
+
+				c = (u8) *s++;
+				if ((c & 0xc0) != 0xc0)
+					goto fail;
+				c &= 0x3f;
+				uchar |= c << 6;
+
+				c = (u8) *s++;
+				if ((c & 0xc0) != 0xc0)
+					goto fail;
+				c &= 0x3f;
+				uchar |= c;
+
+				/* no bogus surrogates */
+				if (0xd800 <= uchar && uchar <= 0xdfff)
+					goto fail;
+
+			// 4-byte sequence (surrogate pairs, currently rare):
+			// 11101110wwwwzzzzyy + 110111yyyyxxxxxx
+			//     = 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
+			// (uuuuu = wwww + 1)
+			// FIXME accept the surrogate code points (only)
+
+			} else
+				goto fail;
+		} else
+			uchar = c;
+		put_unaligned (cpu_to_le16 (uchar), cp++);
+		count++;
+		len--;
+	}
+	return count;
+fail:
+	return -1;
+}
+
+
+/**
+ * usb_gadget_get_string - fill out a string descriptor 
+ * @table: of c strings encoded using UTF-8
+ * @id: string id, from low byte of wValue in get string descriptor
+ * @buf: at least 256 bytes
+ *
+ * Finds the UTF-8 string matching the ID, and converts it into a
+ * string descriptor in utf16-le.
+ * Returns length of descriptor (always even) or negative errno
+ *
+ * If your driver needs stings in multiple languages, you'll probably
+ * "switch (wIndex) { ... }"  in your ep0 string descriptor logic,
+ * using this routine after choosing which set of UTF-8 strings to use.
+ * Note that US-ASCII is a strict subset of UTF-8; any string bytes with
+ * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
+ * characters (which are also widely used in C strings).
+ */
+int
+usb_gadget_get_string (struct usb_gadget_strings *table, int id, u8 *buf)
+{
+	struct usb_string	*s;
+	int			len;
+
+	/* descriptor 0 has the language id */
+	if (id == 0) {
+		buf [0] = 4;
+		buf [1] = USB_DT_STRING;
+		buf [2] = (u8) table->language;
+		buf [3] = (u8) (table->language >> 8);
+		return 4;
+	}
+	for (s = table->strings; s && s->s; s++)
+		if (s->id == id)
+			break;
+
+	/* unrecognized: stall. */
+	if (!s || !s->s)
+		return -EINVAL;
+
+	/* string descriptors have length, tag, then UTF16-LE text */
+	len = min ((size_t) 126, strlen (s->s));
+	memset (buf + 2, 0, 2 * len);	/* zero all the bytes */
+	len = utf8_to_utf16le(s->s, (__le16 *)&buf[2], len);
+	if (len < 0)
+		return -EINVAL;
+	buf [0] = (len + 1) * 2;
+	buf [1] = USB_DT_STRING;
+	return buf [0];
+}
+