usb: re-enable EHCI, share HID keyboard decoding, fix boot protocol

- ehci: DEBUG_MATRIX was left true in be868a4, so every boot replaced
  enumeration with the one-shot diagnostic transfer matrix and returned
  false -- the EHCI driver never brought a device up.  Default it off;
  flip it back on only when bisecting a controller fault.
- new rsnix/src/hid.rs: boot-keyboard HID usage -> scancode-set-1
  tables, the shared scancode FIFO, and a per-device report differ.
  UHCI now uses it instead of its own copy, so EHCI/xHCI keyboards can
  feed the same PS/2 decoder (`ps2::feed_scancode`).
- uhci: SET_PROTOCOL now asks for the boot protocol (wValue 0) instead
  of report protocol (wValue 1).  In report protocol the report layout
  is device-defined, but every driver parses boot reports.

1 files changed, 6 insertions, 1 deletions

diff --git a/rsnix/src/ehci.rs b/rsnix/src/ehci.rs
index 6209155..8baa0ad 100644
--- a/rsnix/src/ehci.rs
+++ b/rsnix/src/ehci.rs
@@ -89,7 +89,12 @@ static QR_SHOWN: AtomicBool = AtomicBool::new(false);
 // DEBUG: run the one-boot transfer variant matrix (real-hardware bisection
 // of the EHCI System Error trigger).  MATRIX_DONE gates it to one pass;
 // XFER_TWEAK flips construction variables inside ctl_xfer.
-static DEBUG_MATRIX: bool = true;
+//
+// OFF in normal builds: with it on, `enumerate()` is replaced by the
+// diagnostic matrix and returns false, i.e. the EHCI driver never brings a
+// device up.  Flip to true only when bisecting a hardware fault, and expect
+// no USB input in that build.
+static DEBUG_MATRIX: bool = false;
 static MATRIX_DONE: AtomicBool = AtomicBool::new(false);
 static XFER_TWEAK: AtomicU32 = AtomicU32::new(0);
 // Low-region (<1 MB) control QH for the matrix's low-region variant.