Make reading of descriptors more robust to support more usb cdc-ecm devices,
and add realtek rtl8152 to usbdb for automatic recognition.
Note: this obsoletes the earlier patch maybe/usb-short-desc

Reference: /n/sources/patch/usb-ether-cdc
Date: Mon Mar 13 09:48:37 GMT 2017
Signed-off-by: miller@hamnavoe.com

--- /sys/src/cmd/usb/ether/cdc.c	Mon Mar 13 09:41:51 2017
+++ /sys/src/cmd/usb/ether/cdc.c	Mon Mar 13 09:41:49 2017
@@ -48,13 +48,29 @@
 int
 cdcreset(Ether *ether)
 {
+	Usbdev *ud;
+	Ep *ep;
+	int i;
+
 	/*
 	 * Assume that all communication devices are going to
 	 * be std. ethernet communication devices. Specific controllers
 	 * must have been probed first.
-	 * NB: This ignores unions.
 	 */
-	if(ether->dev->usb->class == Clcomms)
+	ud = ether->dev->usb;
+	if(ud->class == Clcomms)
 		return getmac(ether);
+	if(getmac(ether) == 0){
+		for(i = 0; i < Nep; i++){
+			ep = ud->ep[i];
+			if(ep == nil)
+				continue;
+			if(ep->iface == nil || !okclass(ep->iface))
+				continue;
+			if(ep->conf->cval != 1)
+				usbcmd(ether->dev, Rh2d|Rstd|Rdev, Rsetconf, ep->conf->cval, 0, nil, 0);
+			return 0;
+		}
+	}
 	return -1;
 }
--- /sys/src/cmd/usb/lib/dev.c	Mon Mar 13 09:41:55 2017
+++ /sys/src/cmd/usb/lib/dev.c	Mon Mar 13 09:41:53 2017
@@ -148,7 +148,7 @@
 loaddevconf(Dev *d, int n)
 {
 	uchar *buf;
-	int nr;
+	int l, nr;
 	int type;
 
 	if(n >= nelem(d->usb->conf)){
@@ -158,11 +158,22 @@
 	}
 	buf = emallocz(Maxdevconf, 0);
 	type = Rd2h|Rstd|Rdev;
-	nr = usbcmd(d, type, Rgetdesc, Dconf<<8|n, 0, buf, Maxdevconf);
+	nr = usbcmd(d, type, Rgetdesc, Dconf<<8|n, 0, buf, Dconflen);
 	if(nr < Dconflen){
 		free(buf);
 		return -1;
 	}
+	l = GET2(((DConf*)buf)->wTotalLength);
+	if(l > Maxdevconf){
+		free(buf);
+		return -1;
+	}
+	nr = usbcmd(d, type, Rgetdesc, Dconf<<8|n, 0, buf, l);
+	if(nr < l){
+		free(buf);
+		return -1;
+	}
+	
 	if(d->usb->conf[n] == nil)
 		d->usb->conf[n] = emallocz(sizeof(Conf), 1);
 	nr = parseconf(d->usb, d->usb->conf[n], buf, nr);
@@ -188,6 +199,8 @@
 	char *s;
 	char *e;
 
+	if(n > b[0])
+		n = b[0];
 	if(n <= 2 || (n & 1) != 0)
 		return strdup("none");
 	n = (n - 2)/2;
@@ -204,42 +217,37 @@
 char*
 loaddevstr(Dev *d, int sid)
 {
-	uchar buf[128];
-	int type;
-	int nr;
+	uchar buf[256];
+	int type, langid, nr;
 
 	if(sid == 0)
 		return estrdup("none");
 	type = Rd2h|Rstd|Rdev;
-	nr=usbcmd(d, type, Rgetdesc, Dstr<<8|sid, 0, buf, sizeof(buf));
+	nr = usbcmd(d, type, Rgetdesc, Dstr<<8|sid, 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);
 }
 
 int
 loaddevdesc(Dev *d)
 {
-	uchar buf[Ddevlen+255];
+	uchar buf[Ddevlen];
 	int nr;
 	int type;
 	Ep *ep0;
 
 	type = Rd2h|Rstd|Rdev;
-	nr = sizeof(buf);
 	memset(buf, 0, Ddevlen);
-	if((nr=usbcmd(d, type, Rgetdesc, Ddev<<8|0, 0, buf, nr)) < 0)
+	if((nr = usbcmd(d, type, Rgetdesc, Ddev<<8|0, 0, buf, Ddevlen)) < 0)
 		return -1;
-	/*
-	 * Several hubs are returning descriptors of 17 bytes, not 18.
-	 * We accept them and leave number of configurations as zero.
-	 * (a get configuration descriptor also fails for them!)
-	 */
 	if(nr < Ddevlen){
-		print("%s: %s: warning: device with short descriptor\n",
-			argv0, d->dir);
-		if(nr < Ddevlen-1){
-			werrstr("short device descriptor (%d bytes)", nr);
-			return -1;
-		}
+		werrstr("short device descriptor (%d bytes)", nr);
+		return -1;
 	}
 	d->usb = emallocz(sizeof(Usbdev), 1);
 	ep0 = mkep(d->usb, 0);
@@ -254,6 +262,8 @@
 			d->usb->serial = loaddevstr(d, d->usb->ssid);
 		}
 	}
+	else
+		print("usbd: desc error: %r");
 	return nr;
 }
 
--- /sys/src/cmd/usb/usbd/usbdb	Mon Mar 13 09:41:59 2017
+++ /sys/src/cmd/usb/usbd/usbdb	Mon Mar 13 09:41:57 2017
@@ -5,6 +5,7 @@
 	disk	class=storage			args=
 	ether	class=255 csp=0x00ffff vid=0x0b95		args=
 	ether	class=255 csp=0xff00ff vid=0x0424 did=0xec00	args=
+	ether	class=255 csp=0x000602 vid=0x0bda did=0x8152	args=
 	serial	class=255 csp=0xffffff vid=0x9e88 did=0x9e8f	args=
 	serial	class=255 csp=0xffffff vid=0x0403		args=
 	serial	class=255 csp=0x0000ff vid=0x10c4	args=