v0.5.10: USB HID mouse via polled xHCI (rsnix/src/usb.rs)

Polled xHCI driver (mouse-only): controller bring-up, port reset,
enable-slot -> address-device -> config-descriptor walk -> HID boot
mouse IN endpoint, one outstanding IN TRB drained on poll.  Cursor
task polls usb first, PS/2 second.  New 'usb'/'usb rescan' shell cmds.

Verified in QEMU (q35 + OVMF + qemu-xhci + usb-mouse): movement and
all three buttons tracked exactly; heap stays clean.

Fixes en route: MaxPorts=HCSPARAMS1[31:24]; operational regs CRCR=0x18
DCBAAP=0x30 CONFIG=0x38; pass input-context ptr in Address-Device;
Input Control Context DW0=Drop DW1=Add; HID walker bInterfaceClass at
+5; async discovery from cursor task.

1 files changed, 19 insertions, 0 deletions

diff --git a/shell/src/lib.rs b/shell/src/lib.rs
index 0f5ac4b..c9b7cdd 100644
--- a/shell/src/lib.rs
+++ b/shell/src/lib.rs
@@ -721,6 +721,7 @@ write `{} <path> TIL <marker>`",
         "stress" => cmd_stress(&parsed),
         "date" => cmd_date(&parsed),
         "pci" => cmd_pci(&parsed),
+        "usb" => cmd_usb(&parsed),
         "rescan" => cmd_rescan(&parsed),
         "mouse" => cmd_mouse(&parsed),
         "cursor" => cmd_cursor(&parsed),
@@ -2217,6 +2218,24 @@ fn cmd_pci(p: &Parsed) {
     pipe.end();
 }
 
+fn cmd_usb(p: &Parsed) {
+    // `usb rescan` clears the failed-port mask so discovery retries.
+    if p.args.first().is_some_and(|w| w == "rescan") {
+        rsnix::usb::rescan();
+        let mut pipe = Pipeline::new(&p.filters, &p.output);
+        let _ = pipe.line("usb: rescanning ports");
+        pipe.end();
+        return;
+    }
+    let mut pipe = Pipeline::new(&p.filters, &p.output);
+    for l in rsnix::usb::diagnose().lines() {
+        if !pipe.line(l) {
+            break;
+        }
+    }
+    pipe.end();
+}
+
 fn cmd_poweroff() -> ! {
     term_println("shutting down...");
     rsnix::power::poweroff()