ChangeSet 1.1290.15.18, 2004/03/03 10:04:33-08:00, [EMAIL PROTECTED]
[PATCH] USB Gadget: make usb gadget strings talk utf-8
Teach gadget/usbstring to expect UTF-8 strings, not ISO-8859/1 ones.
This just gets rid of an API issue: no hacks needed for non-Western
languages, and multi-language support will be lots easier.
Current drivers won't notice the API change, they use US-ASCII (which
is a strict superset of both encodings).
Future drivers may want to teach utf8_to_utf16le() about the four-byte
encodings, so they can emit surrogate pairs for those Unicode characters.
drivers/usb/gadget/usbstring.c | 92 ++++++++++++++++++++++++++++++++++-------
include/linux/usb_gadget.h | 2
2 files changed, 79 insertions(+), 15 deletions(-)
diff -Nru a/drivers/usb/gadget/usbstring.c b/drivers/usb/gadget/usbstring.c
--- a/drivers/usb/gadget/usbstring.c Wed Mar 17 15:48:29 2004
+++ b/drivers/usb/gadget/usbstring.c Wed Mar 17 15:48:29 2004
@@ -16,24 +16,89 @@
#include <linux/usb_ch9.h>
#include <linux/usb_gadget.h>
+#include <asm/unaligned.h>
+
+
+static int utf8_to_utf16le(const char *s, u16 *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 using iso latin/1 characters
+ * @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 iso latin/1 string matching the ID, and converts it into a
+ * 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 need to
- * to use some alternate solution for languages where the ISO 8859/1
- * (latin/1) character set can't be used. For example, they can't be
- * used with Chinese (Big5, GB2312, etc), Japanese, Korean, or many other
- * languages. You'd likely "switch (wIndex) { ... }" in your ep0
- * string descriptor logic, using this routine in cases where "western
- * european" characters suffice for the strings being returned.
+ * 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)
@@ -59,13 +124,12 @@
/* 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, (u16 *)&buf[2], len);
+ if (len < 0)
+ return -EINVAL;
buf [0] = (len + 1) * 2;
buf [1] = USB_DT_STRING;
- memset (buf + 2, 0, 2 * len); /* zero all the high bytes */
- while (len) {
- buf [2 * len] = s->s [len - 1];
- len--;
- }
return buf [0];
}
diff -Nru a/include/linux/usb_gadget.h b/include/linux/usb_gadget.h
--- a/include/linux/usb_gadget.h Wed Mar 17 15:48:29 2004
+++ b/include/linux/usb_gadget.h Wed Mar 17 15:48:29 2004
@@ -707,7 +707,7 @@
/**
* struct usb_string - wraps a C string and its USB id
* @id:the (nonzero) ID for this string
- * @s:the string, in ISO-8859/1 characters
+ * @s:the string, in UTF-8 encoding
*
* If you're using usb_gadget_get_string(), use this to wrap a string
* together with its ID.
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