nlm: Ensure callback code also checks that the files match

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / include / linux / usb.h

diff --git a/include/linux/usb.h b/include/linux/usb.h
index a0bee5a28d1a578a27829edd231968e1ff11ce1d..28bd3a898cba11b090dbe0fe6d21604ae268889c 100644 (file)
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -206,6 +206,32 @@ void usb_put_intf(struct usb_interface *intf);
 #define USB_MAXINTERFACES      32
 #define USB_MAXIADS            (USB_MAXINTERFACES/2)
 
+/*
+ * USB Resume Timer: Every Host controller driver should drive the resume
+ * signalling on the bus for the amount of time defined by this macro.
+ *
+ * That way we will have a 'stable' behavior among all HCDs supported by Linux.
+ *
+ * Note that the USB Specification states we should drive resume for *at least*
+ * 20 ms, but it doesn't give an upper bound. This creates two possible
+ * situations which we want to avoid:
+ *
+ * (a) sometimes an msleep(20) might expire slightly before 20 ms, which causes
+ * us to fail USB Electrical Tests, thus failing Certification
+ *
+ * (b) Some (many) devices actually need more than 20 ms of resume signalling,
+ * and while we can argue that's against the USB Specification, we don't have
+ * control over which devices a certification laboratory will be using for
+ * certification. If CertLab uses a device which was tested against Windows and
+ * that happens to have relaxed resume signalling rules, we might fall into
+ * situations where we fail interoperability and electrical tests.
+ *
+ * In order to avoid both conditions, we're using a 40 ms resume timeout, which
+ * should cope with both LPJ calibration errors and devices not following every
+ * detail of the USB Specification.
+ */
+#define USB_RESUME_TIMEOUT     40 /* ms */
+
 /**
  * struct usb_interface_cache - long-term representation of a device interface
  * @num_altsetting: number of altsettings defined.