Greg:
This patch make the hub driver's device initialization routine more
aggressive about detecting errors and retrying. It checks the result of
the 64-byte GET-DESCRIPTOR request to verify that the descriptor tag is
set correctly and the ep0-maxpacket value is legal; if either is not true
it will retry the request immediately. David Brownell has said that this
kind of approach is necessary to make certain buggy devices work.
Alan Stern
Signed-off-by: Alan Stern <[EMAIL PROTECTED]>
===== drivers/usb/core/hub.c 1.223 vs edited =====
--- 1.223/drivers/usb/core/hub.c 2005-01-11 12:14:56 -05:00
+++ edited/drivers/usb/core/hub.c 2005-01-13 11:51:32 -05:00
@@ -2180,24 +2180,35 @@
retval = -ENOMEM;
continue;
}
- buf->bMaxPacketSize0 = 0;
/* Use a short timeout the first time through,
* so that recalcitrant full-speed devices with
* 8- or 16-byte ep0-maxpackets won't slow things
* down tremendously by NAKing the unexpectedly
- * early status stage. Also, retry on length 0
- * or stall; some devices are flakey.
+ * early status stage. Also, retry on all errors;
+ * some devices are flakey.
*/
for (j = 0; j < 3; ++j) {
+ buf->bMaxPacketSize0 = 0;
r = usb_control_msg(udev, usb_rcvaddr0pipe(),
USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
USB_DT_DEVICE << 8, 0,
buf, GET_DESCRIPTOR_BUFSIZE,
(i ? HZ * USB_CTRL_GET_TIMEOUT : HZ));
- if (r == 0 || r == -EPIPE)
- continue;
- if (r < 0)
+ switch (buf->bMaxPacketSize0) {
+ case 8: case 16: case 32: case 64:
+ if (buf->bDescriptorType ==
+ USB_DT_DEVICE) {
+ r = 0;
+ break;
+ }
+ /* FALL THROUGH */
+ default:
+ if (r == 0)
+ r = -EPROTO;
+ break;
+ }
+ if (r == 0)
break;
}
udev->descriptor.bMaxPacketSize0 =
@@ -2213,10 +2224,7 @@
retval = -ENODEV;
goto fail;
}
- switch (udev->descriptor.bMaxPacketSize0) {
- case 64: case 32: case 16: case 8:
- break;
- default:
+ if (r) {
dev_err(&udev->dev, "device descriptor "
"read/%s, error %d\n",
"64", r);
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