Remove the shim kernel crate

kernel/src/device/null.rs

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MPL-2.0
+
+#![allow(unused_variables)]
+
+use super::*;
+use crate::{events::IoEvents, fs::inode_handle::FileIo, prelude::*, process::signal::Poller};
+
+pub struct Null;
+
+impl Device for Null {
+    fn type_(&self) -> DeviceType {
+        DeviceType::CharDevice
+    }
+
+    fn id(&self) -> DeviceId {
+        // Same value with Linux
+        DeviceId::new(1, 3)
+    }
+}
+
+impl FileIo for Null {
+    fn read(&self, _writer: &mut VmWriter) -> Result<usize> {
+        Ok(0)
+    }
+
+    fn write(&self, reader: &mut VmReader) -> Result<usize> {
+        Ok(reader.remain())
+    }
+
+    fn poll(&self, mask: IoEvents, poller: Option<&mut Poller>) -> IoEvents {
+        let events = IoEvents::IN | IoEvents::OUT;
+        events & mask
+    }
+}