xhcid: P0-A4 — bounds-check root_hub_port_index() calls

Replace 5 bare unwrap() / index-operator sites on root_hub_port_index()
with bounded access:
  get_pls():    expect() with diagnostic (returns u8, can't use ?)
  poll():       match None → continue
  print_port:   match None → continue
  reset_port(): ok_or_else(|| Error::new(EINVAL))? (returns Result)
  attach:       ok_or_else(|| Error::new(EINVAL))? (returns Result)

Added EINVAL to syscall::error import.

drivers/usb/xhcid/src/xhci/mod.rs

@@ -16,7 +16,7 @@ use std::sync::atomic::AtomicUsize;
 use std::sync::{Arc, Mutex};
 
 use std::{mem, process, slice, thread};
-use syscall::error::{Error, Result, EBADF, EBADMSG, EIO, ENOENT};
+use syscall::error::{Error, Result, EBADF, EBADMSG, EINVAL, EIO, ENOENT};
 use syscall::{EAGAIN, PAGE_SIZE};
 
 use chashmap::CHashMap;
@@ -600,7 +600,8 @@ impl<const N: usize> Xhci<N> {
 
     pub fn get_pls(&self, port_id: PortId) -> u8 {
         let mut ports = self.ports.lock().unwrap();
-        let port = ports.get_mut(port_id.root_hub_port_index()).unwrap();
+        let port = ports.get_mut(port_id.root_hub_port_index())
+            .expect("get_pls: port index out of range");
         port.state()
     }
 
@@ -618,7 +619,10 @@ impl<const N: usize> Xhci<N> {
             //Get the CCS and CSC flags
             let (ccs, csc, flags) = {
                 let mut ports = self.ports.lock().unwrap();
-                let port = &mut ports[port_id.root_hub_port_index()];
+                let port = match ports.get_mut(port_id.root_hub_port_index()) {
+                    Some(p) => p,
+                    None => continue,
+                };
                 let flags = port.flags();
                 let ccs = flags.contains(PortFlags::CCS);
                 let csc = flags.contains(PortFlags::CSC);
@@ -660,7 +664,10 @@ impl<const N: usize> Xhci<N> {
             {
                 let mut ports = self.ports.lock().unwrap();
 
-                flags = ports[port_id.root_hub_port_index()].flags();
+                flags = match ports.get(port_id.root_hub_port_index()) {
+                    Some(p) => p.flags(),
+                    None => continue,
+                };
             }
 
             match self.supported_protocol(port_id) {
@@ -686,7 +693,8 @@ impl<const N: usize> Xhci<N> {
 
         //TODO handle the second unwrap
         let mut ports = self.ports.lock().unwrap();
-        let port = ports.get_mut(port_id.root_hub_port_index()).unwrap();
+        let port = ports.get_mut(port_id.root_hub_port_index())
+            .ok_or_else(|| Error::new(EINVAL))?;
         let instant = std::time::Instant::now();
 
         debug!("Port {} Link State: {}", port_id, port.state());
@@ -799,7 +807,9 @@ impl<const N: usize> Xhci<N> {
         }
 
         let (data, state, speed, flags) = {
-            let port = &self.ports.lock().unwrap()[port_id.root_hub_port_index()];
+            let port = self.ports.lock().unwrap();
+            let port = port.get(port_id.root_hub_port_index())
+                .ok_or_else(|| Error::new(EINVAL))?;
             (port.read(), port.state(), port.speed(), port.flags())
         };