devices: Introduce remove() for bus

When device's bar is reallocated, the old ranges will be deleted,
this commit add remove() function to delete one old range from
bus->devices.

BUG=b:174705596
TEST=Boot a vm, monitor Bar Reallocation then check function

Change-Id: Id0600ae1d7a3d04c7f05a90abcc8807b7f1020c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3184725
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

devices/src/bus.rs

@@ -150,6 +150,8 @@ pub trait BusDeviceObj {
 #[sorted]
 #[derive(Error, Debug)]
 pub enum Error {
+    #[error("Bus Range not found")]
+    Empty,
     /// The insertion failed because the new device overlapped with an old device.
     #[error("new device overlaps with an old device")]
     Overlap,
@@ -295,6 +297,28 @@ impl Bus {
         Ok(())
     }
 
+    /// Remove the given device at the given address space.
+    pub fn remove(&self, base: u64, len: u64) -> Result<()> {
+        if len == 0 {
+            return Err(Error::Overlap);
+        }
+
+        let mut devices = self.devices.lock();
+        if devices
+            .iter()
+            .any(|(range, _dev)| range.base == base && range.len == len)
+        {
+            let ret = devices.remove(&BusRange { base, len });
+            if ret.is_some() {
+                Ok(())
+            } else {
+                Err(Error::Empty)
+            }
+        } else {
+            Err(Error::Empty)
+        }
+    }
+
     /// Reads data from the device that owns the range containing `addr` and puts it into `data`.
     ///
     /// Returns true on success, otherwise `data` is untouched.