clippy: Resolve single_match

TEST=bin/clippy

Change-Id: Iea0d3539b3ab587a2d97f676e1d9c7a239504308
Reviewed-on: https://chromium-review.googlesource.com/1566748
Commit-Ready: David Tolnay <dtolnay@chromium.org>
Tested-by: David Tolnay <dtolnay@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

3 files changed, 34 insertions, 41 deletions

diff --git a/devices/src/usb/host_backend/context.rs b/devices/src/usb/host_backend/context.rs
index bf4a13d..960d066 100644
--- a/devices/src/usb/host_backend/context.rs
+++ b/devices/src/usb/host_backend/context.rs
@@ -129,32 +129,29 @@ struct PollfdChangeHandler {
 
 impl LibUsbPollfdChangeHandler for PollfdChangeHandler {
     fn add_poll_fd(&self, fd: RawFd, events: c_short) {
-        match self.event_loop.add_event(
+        if let Err(e) = self.event_loop.add_event(
             &MaybeOwnedFd::Borrowed(fd),
             WatchingEvents::new(events as u32),
             self.event_handler.clone(),
         ) {
-            Err(e) => error!("cannot add event to event loop: {}", e),
-            Ok(_) => {}
+            error!("cannot add event to event loop: {}", e);
         }
     }
 
     fn remove_poll_fd(&self, fd: RawFd) {
         if let Some(h) = self.event_handler.upgrade() {
-            match h.on_event() {
-                Ok(()) => {}
-                Err(e) => error!("cannot handle event: {:?}", e),
+            if let Err(e) = h.on_event() {
+                error!("cannot handle event: {:?}", e);
             }
         }
-        match self
+        if let Err(e) = self
             .event_loop
             .remove_event_for_fd(&MaybeOwnedFd::Borrowed(fd))
         {
-            Ok(_) => {}
-            Err(e) => error!(
+            error!(
                 "failed to remove poll change handler from event loop: {}",
                 e
-            ),
+            );
         }
     }
 }
diff --git a/devices/src/usb/host_backend/hotplug.rs b/devices/src/usb/host_backend/hotplug.rs
index 673acce..0764660 100644
--- a/devices/src/usb/host_backend/hotplug.rs
+++ b/devices/src/usb/host_backend/hotplug.rs
@@ -21,26 +21,25 @@ impl HotplugHandler {
 
 impl UsbHotplugHandler for HotplugHandler {
     fn hotplug_event(&self, device: LibUsbDevice, event: HotplugEvent) {
-        match event {
-            HotplugEvent::DeviceLeft => {
-                let bus = device.get_bus_number();
-                let address = device.get_address();
-                let descriptor = match device.get_device_descriptor() {
-                    Ok(d) => d,
-                    Err(e) => {
-                        error!("cannot get device descriptor: {:?}", e);
-                        return;
-                    }
-                };
-                let vid = descriptor.idVendor;
-                let pid = descriptor.idProduct;
+        if event != HotplugEvent::DeviceLeft {
+            return;
+        }
 
-                if let Err(e) = self.hub.try_detach(bus, address, vid, pid) {
-                    error!("device left event triggered failed detach from hub: {}", e);
-                    return;
-                }
+        let bus = device.get_bus_number();
+        let address = device.get_address();
+        let descriptor = match device.get_device_descriptor() {
+            Ok(d) => d,
+            Err(e) => {
+                error!("cannot get device descriptor: {:?}", e);
+                return;
             }
-            _ => {}
+        };
+        let vid = descriptor.idVendor;
+        let pid = descriptor.idProduct;
+
+        if let Err(e) = self.hub.try_detach(bus, address, vid, pid) {
+            error!("device left event triggered failed detach from hub: {}", e);
+            return;
         }
     }
 }
diff --git a/devices/src/usb/xhci/ring_buffer.rs b/devices/src/usb/xhci/ring_buffer.rs
index 2f66fa8..5e2c570 100644
--- a/devices/src/usb/xhci/ring_buffer.rs
+++ b/devices/src/usb/xhci/ring_buffer.rs
@@ -67,19 +67,16 @@ impl RingBuffer {
     pub fn dequeue_transfer_descriptor(&mut self) -> Result<Option<TransferDescriptor>> {
         let mut td: TransferDescriptor = TransferDescriptor::new();
         while let Some(addressed_trb) = self.get_current_trb()? {
-            match addressed_trb.trb.trb_type() {
-                Ok(TrbType::Link) => {
-                    let link_trb = addressed_trb
-                        .trb
-                        .cast::<LinkTrb>()
-                        .map_err(Error::CastTrb)?;
-                    self.dequeue_pointer = GuestAddress(link_trb.get_ring_segment_pointer());
-                    self.consumer_cycle_state =
-                        self.consumer_cycle_state != link_trb.get_toggle_cycle_bit();
-                    continue;
-                }
-                _ => {}
-            };
+            if let Ok(TrbType::Link) = addressed_trb.trb.trb_type() {
+                let link_trb = addressed_trb
+                    .trb
+                    .cast::<LinkTrb>()
+                    .map_err(Error::CastTrb)?;
+                self.dequeue_pointer = GuestAddress(link_trb.get_ring_segment_pointer());
+                self.consumer_cycle_state =
+                    self.consumer_cycle_state != link_trb.get_toggle_cycle_bit();
+                continue;
+            }
 
             self.dequeue_pointer = match self.dequeue_pointer.checked_add(size_of::<Trb>() as u64) {
                 Some(addr) => addr,