-/* Return the size of the buffer needed to hold a string of len x formatted
- * for send to CP210X, and its reverse.
- */
-#define USBSTRLEN(strlen) (strlen * 2 + 2)
+/* Taken from drivers/usb/gadget/usbstring.c */
+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) != 0x80)
+ 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) != 0x80)
+ goto fail;
+ c &= 0x3f;
+ uchar |= c << 6;
+
+ c = (u8) *s++;
+ if ((c & 0xc0) != 0x80)
+ 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;
+ *cp++ = uchar;
+ count++;
+ len--;
+ }
+ return count;
+fail:
+ return -1;
+}