[linux-usb-devel] [patch 2.6.5] usb, retry some descriptor fetches

[David Brownell]

This helps Linux handle certain enumeration problems better,
by retrying most stalled descriptor fetches; on some devices,
those indicate temporary problems.  This match makes at least
one such (old) device enumerate reliably.
Please merge.

- Dave

--- 1.49/drivers/usb/core/message.c     Wed Mar 31 14:27:07 2004
+++ edited/drivers/usb/core/message.c   Tue Apr  6 09:52:25 2004
@@ -572,13 +572,16 @@
        memset(buf,0,size);     // Make sure we parse really received data
 
        while (i--) {
-               /* retries if the returned length was 0; flakey device */
+               /* retry on length 0 or stall; some devices are flakey */
                if ((result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
                                    USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
                                    (type << 8) + index, 0, buf, size,
                                    HZ * USB_CTRL_GET_TIMEOUT)) > 0
-                               || result == -EPIPE)
+                               || result != -EPIPE)
                        break;
+
+               dev_dbg (&dev->dev, "RETRY descriptor, result %d\n", result);
+               result = -ENOMSG;
        }
        return result;
 }
@@ -1244,7 +1247,7 @@
 
        /* get langid for strings if it's not yet known */
        if (!dev->have_langid) {
-               err = usb_get_string(dev, 0, 0, tbuf, 4);
+               err = usb_get_descriptor(dev, USB_DT_STRING, 0, tbuf, 4);
                if (err < 0) {
                        dev_err (&dev->dev,
                                "string descriptor 0 read error: %d\n",
@@ -1268,11 +1271,19 @@
         */
 
        err = usb_get_string(dev, dev->string_langid, index, tbuf, 2);
+       if (err == -EPIPE) {
+               dev_dbg(&dev->dev, "RETRY string %d read/%d\n", index, 2);
+               err = usb_get_string(dev, dev->string_langid, index, tbuf, 2);
+       }
        if(err<2)
                goto errout;
        len=tbuf[0];    
        
        err = usb_get_string(dev, dev->string_langid, index, tbuf, len);
+       if (err == -EPIPE) {
+               dev_dbg(&dev->dev, "RETRY string %d read/%d\n", index, len);
+               err = usb_get_string(dev, dev->string_langid, index, tbuf, len);
+       }
        if (err < 0)
                goto errout;