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Diffstat (limited to 'drivers/usb/early/xhci-dbc.h')
-rw-r--r--drivers/usb/early/xhci-dbc.h18
1 files changed, 16 insertions, 2 deletions
diff --git a/drivers/usb/early/xhci-dbc.h b/drivers/usb/early/xhci-dbc.h
index 673686eeddd7..6e2b7266a695 100644
--- a/drivers/usb/early/xhci-dbc.h
+++ b/drivers/usb/early/xhci-dbc.h
@@ -120,8 +120,22 @@ struct xdbc_ring {
u32 cycle_state;
};
-#define XDBC_EPID_OUT 2
-#define XDBC_EPID_IN 3
+/*
+ * These are the "Endpoint ID" (also known as "Context Index") values for the
+ * OUT Transfer Ring and the IN Transfer Ring of a Debug Capability Context data
+ * structure.
+ * According to the "eXtensible Host Controller Interface for Universal Serial
+ * Bus (xHCI)" specification, section "7.6.3.2 Endpoint Contexts and Transfer
+ * Rings", these should be 0 and 1, and those are the values AMD machines give
+ * you; but Intel machines seem to use the formula from section "4.5.1 Device
+ * Context Index", which is supposed to be used for the Device Context only.
+ * Luckily the values from Intel don't overlap with those from AMD, so we can
+ * just test for both.
+ */
+#define XDBC_EPID_OUT 0
+#define XDBC_EPID_IN 1
+#define XDBC_EPID_OUT_INTEL 2
+#define XDBC_EPID_IN_INTEL 3
struct xdbc_state {
u16 vendor;