USB: replace hardcode maximum usb string length by definition

Replace hardcoded maximum USB string length (126 bytes) by definition
"USB_MAX_STRING_LEN".
Signed-off-by: Macpaul Lin <macpaul.lin@mediatek.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/1592471618-29428-1-git-send-email-macpaul.lin@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/composite.c

@@ -1085,7 +1085,7 @@ static void collect_langs(struct usb_gadget_strings **sp, __le16 *buf)
 	while (*sp) {
 		s = *sp;
 		language = cpu_to_le16(s->language);
-		for (tmp = buf; *tmp && tmp < &buf[126]; tmp++) {
+		for (tmp = buf; *tmp && tmp < &buf[USB_MAX_STRING_LEN]; tmp++) {
 			if (*tmp == language)
 				goto repeat;
 		}
@@ -1160,7 +1160,7 @@ static int get_string(struct usb_composite_dev *cdev,
 			collect_langs(sp, s->wData);
 		}
 
-		for (len = 0; len <= 126 && s->wData[len]; len++)
+		for (len = 0; len <= USB_MAX_STRING_LEN && s->wData[len]; len++)
 			continue;
 		if (!len)
 			return -EINVAL;

drivers/usb/gadget/configfs.c

@@ -103,7 +103,7 @@ static int usb_string_copy(const char *s, char **s_copy)
 	char *str;
 	char *copy = *s_copy;
 	ret = strlen(s);
-	if (ret > 126)
+	if (ret > USB_MAX_STRING_LEN)
 		return -EOVERFLOW;
 
 	str = kstrdup(s, GFP_KERNEL);

drivers/usb/gadget/usbstring.c

@@ -55,9 +55,9 @@ usb_gadget_get_string (const struct usb_gadget_strings *table, int id, u8 *buf)
 		return -EINVAL;
 
 	/* string descriptors have length, tag, then UTF16-LE text */
-	len = min ((size_t) 126, strlen (s->s));
+	len = min((size_t)USB_MAX_STRING_LEN, strlen(s->s));
 	len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
-			(wchar_t *) &buf[2], 126);
+			(wchar_t *) &buf[2], USB_MAX_STRING_LEN);
 	if (len < 0)
 		return -EINVAL;
 	buf [0] = (len + 1) * 2;

include/uapi/linux/usb/ch9.h

@@ -368,6 +368,9 @@ struct usb_config_descriptor {
 
 /*-------------------------------------------------------------------------*/
 
+/* USB String descriptors can contain at most 126 characters. */
+#define USB_MAX_STRING_LEN	126
+
 /* USB_DT_STRING: String descriptor */
 struct usb_string_descriptor {
 	__u8  bLength;