bLength can only have values up to 255. bLength and bDescriptorType
takes 2 bytes. So there are (255 - 2) / 2 = 126.5 words for bString

strlen(string) is the lenghts without terminating NUL,
USB_MAX_STRING_LEN includes it.

I am wrong?


Index: usb.h
================================================== =================
RCS file: /var/cvs/src/sys/dev/usb/usb.h,v
retrieving revision 1.28
diff -u -r1.28 usb.h
--- usb.h 17 Jun 2007 07:53:11 -0000 1.28
+++ usb.h 22 Jul 2007 16:06:08 -0000
@@ -254,9 +254,9 @@
typedef struct {
uByte bLength;
uByte bDescriptorType;
- uWord bString[127];
+ uWord bString[126];
} __packed usb_string_descriptor_t;
-#define USB_MAX_STRING_LEN 128
+#define USB_MAX_STRING_LEN 127
#define USB_LANGUAGE_TABLE 0 /* # of the string language id table */

/* Hub specific request */
Index: usbf_subr.c
================================================== =================
RCS file: /var/cvs/src/sys/dev/usb/usbf_subr.c,v
retrieving revision 1.9
diff -u -r1.9 usbf_subr.c
--- usbf_subr.c 15 Jun 2007 11:41:48 -0000 1.9
+++ usbf_subr.c 22 Jul 2007 16:06:08 -0000
@@ -308,8 +308,8 @@
dev->string_id == USBF_STRING_ID_MAX)
return USBF_EMPTY_STRING_ID;

- if ((len = strlen(string)) > USB_MAX_STRING_LEN)
- len = USB_MAX_STRING_LEN;
+ if ((len = strlen(string)) >= USB_MAX_STRING_LEN)
+ len = USB_MAX_STRING_LEN - 1;

oldsize = dev->sdesc_size;
newsize = oldsize + 2 + 2 * len;