USB2/1.1 (EHCI/UHCI) drivers + real-hardware bring-up hardening

- Add polled EHCI (USB2) and UHCI (USB1.1) host-controller drivers with
  HID boot mouse support, wired into cursor polling and the 'usb' shell cmd
- Add USB Legacy ownership handoff (claim_usb_legacy) plus config_write_byte
- Harden boot: verify the PIT/timer ticks before shell entry, EOI stray
  interrupts in the LAPIC to stop interrupt storms, bound PS/2 controller
  waits, and INTx-disable AHCI (polled driver)
- Add boot stage markers, klog screen echo, and QR lock; scheduler
  mark_shell_running; NO_USB stopgap to keep BIOS USB-Legacy input alive
- alloc_pages_above for DMA buffers that must avoid low conventional memory
- Expand DEBUG_NOTES with EHCI/QEMU bring-up findings

1 files changed, 10 insertions, 1 deletions

diff --git a/shell/src/lib.rs b/shell/src/lib.rs
index a54f338..bb048d8 100644
--- a/shell/src/lib.rs
+++ b/shell/src/lib.rs
@@ -2239,9 +2239,10 @@ fn cmd_pci(p: &Parsed) {
 }
 
 fn cmd_usb(p: &Parsed) {
-    // `usb rescan` clears the failed-port mask so discovery retries.
+    // `usb rescan` clears the failed-port masks so discovery retries.
     if p.args.first().is_some_and(|w| w == "rescan") {
         rsnix::usb::rescan();
+        rsnix::ehci::rescan();
         let mut pipe = Pipeline::new(&p.filters, &p.output);
         let _ = pipe.line("usb: rescanning ports");
         pipe.end();
@@ -2262,6 +2263,14 @@ fn cmd_usb(p: &Parsed) {
         }
     }
     pipe.end();
+    // UHCI (USB1.1 companion) — full/low-speed keyboards and mice.
+    let mut pipe = Pipeline::new(&p.filters, &p.output);
+    for l in rsnix::uhci::diagnose().lines() {
+        if !pipe.line(l) {
+            break;
+        }
+    }
+    pipe.end();
 }
 
 fn cmd_poweroff() -> ! {