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nusb: provide language id when reading string descriptors (thanks ftrvxmtrx)

there are devices which do not return a string if used
with invalid language id, so at least try to use the first
one and choose english if failed.

this fixes CDC ethernet for N900

--- a/sys/src/cmd/nusb/lib/dev.c

+++ b/sys/src/cmd/nusb/lib/dev.c

@@ -205,6 +205,7 @@

 loaddevstr(Dev *d, int sid)

 {

 	uchar buf[128];

+	int langid;

 	int type;

 	int nr;

@@ -211,7 +212,19 @@

 	if(sid == 0)

 		return estrdup("none");

 	type = Rd2h|Rstd|Rdev;

-	nr=usbcmd(d, type, Rgetdesc, Dstr<<8|sid, 0, buf, sizeof(buf));

+

+	/*

+	 * there are devices which do not return a string if used

+	 * with invalid language id, so at least try to use the first

+	 * one and choose english if failed

+	 */

+	nr=usbcmd(d, type, Rgetdesc, Dstr<<8, 0, buf, sizeof(buf));

+	if(nr < 4)

+		langid = 0x0409;	// english

+	else

+		langid = buf[3]<<8|buf[2];

+

+	nr=usbcmd(d, type, Rgetdesc, Dstr<<8|sid, langid, buf, sizeof(buf));

 	return mkstr(buf, nr);

 }

-- 

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