From: Marius C Silaghi <msila...@fit.edu>
This patch is generated against the last kernel version in the github kernel
repository.
Some older families of USB2 cameras (STC-XXXXXUSB) do not support querying only
the first 8 bytes of their
device descriptor and therefore fail at enumeration on USB3 HCDs, with babble
error -75 as they send more than
the expected 8 bytes. The proposed patch extends the mechanism used for non
USB3 HCDs in the first part of
the same function, and successively tries to query both the 8 byte prefix of
the device descriptor, as well as
the whole device descriptor (in case the old style query of the 8 byte prefix
fails).
In fact, for the cameras I try to fix, the preferred condition is the negation
of the one in the proposed patch,
"if (!USE_NEW_SCHEME(retry_counter))", to try first the version successful on
this case, but I keep the
current order of the "if" branches to ensure clean continuation of support for
other supported devices.
Signed-off-by: Marius C Silaghi <msila...@fit.edu>
---
--- linux/drivers/usb/core/hub.c.orig 2013-12-23 22:09:50.545093470 -0500
+++ linux/drivers/usb/core/hub.c 2013-12-23 22:29:40.521043702 -0500
@@ -4197,7 +4197,19 @@ hub_port_init (struct usb_hub *hub, stru
break;
}
- retval = usb_get_device_descriptor(udev, 8);
+ /* Try first the old 8-byte query (since it may be expected
+ * by some devices), but then give at least a chance to the
+ * new form (retrieving the whole descriptor)!
+ * Querying the content of the whole structure is required
+ * for older USB2 video cameras which do not support partial
+ * descriptor queries, like the STC-XXXUSB family.
+ * Windows also supports them.
+ */
+ if (USE_NEW_SCHEME(retry_counter))
+ retval = usb_get_device_descriptor(udev, 8);
+ else
+ retval = usb_get_device_descriptor(udev,
+ sizeof(struct usb_device_descriptor));
if (retval < 8) {
if (retval != -ENODEV)
dev_err(&udev->dev,
--
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