On Fri, 7 Jan 2005, David Brownell wrote:
> That patch looked OK, but I might prefer one that also validated
> the ep0 maxpacket size too. (The patch I sent _only_ validated
> that field.) How about something more like
>
> if (r < 8 || buf->bDescriptorType != USB_DT_DEVICE) {
> r = -EPROTO;
> continue;
> }
> switch (buf->bMaxPacketSize0) {
> case 8: case 16: case 32: case 64: break;
> default:
> r = -EPROTO;
> continue;
> }
>
> No real point in accepting a read of 3 bytes and then relying
> on the non-existent 8th byte ... or relying on obviously borked
> data in that byte!
Okay, here's a patch that looks pretty good to me. The only thing I'm not
sure about is that it may retry _too_ aggressively. If you like it I'll
submit it to Greg.
Alan Stern
===== 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
@@ -75,7 +75,7 @@
MODULE_PARM_DESC(old_scheme_first,
"start with the old device initialization scheme");
-static int use_both_schemes = 0;
+static int use_both_schemes = 1;
module_param(use_both_schemes, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(use_both_schemes,
"try the other device initialization scheme if the "
@@ -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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