perf(serial): forward serial read to VecDeque impl

Cargo.toml

@@ -120,7 +120,7 @@ bitflags = "2"
 build-time = "0.1.3"
 cfg-if = "1"
 crossbeam-utils = { version = "0.8", default-features = false }
-embedded-io = "0.7"
+embedded-io = { version = "0.7", features = ["alloc"] }
 enum_dispatch = "0.3"
 fdt = { version = "0.1", features = ["pretty-printing"] }
 free-list = "0.3"

src/arch/aarch64/kernel/serial.rs

@@ -59,25 +59,13 @@ impl ErrorType for SerialDevice {
 
 impl Read for SerialDevice {
 	fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
-		let mut guard = UART_DEVICE.lock();
-
-		if guard.buffer.is_empty() {
-			Ok(0)
-		} else {
-			let min = buf.len().min(guard.buffer.len());
-
-			for (dst, src) in buf[..min].iter_mut().zip(guard.buffer.drain(..min)) {
-				*dst = src;
-			}
-
-			Ok(min)
-		}
+		Ok(UART_DEVICE.lock().buffer.read(buf)?)
 	}
 }
 
 impl ReadReady for SerialDevice {
 	fn read_ready(&mut self) -> Result<bool, Self::Error> {
-		Ok(!UART_DEVICE.lock().buffer.is_empty())
+		Ok(UART_DEVICE.lock().buffer.read_ready()?)
 	}
 }
 

src/arch/x86_64/kernel/serial.rs

@@ -1,5 +1,4 @@
 use alloc::collections::VecDeque;
-use alloc::vec::Vec;
 
 use embedded_io::{ErrorType, Read, ReadReady, Write};
 use hermit_sync::{InterruptTicketMutex, Lazy};
@@ -52,22 +51,13 @@ impl ErrorType for SerialDevice {
 
 impl Read for SerialDevice {
 	fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
-		let mut guard = UART_DEVICE.lock();
-		if guard.buffer.is_empty() {
-			Ok(0)
-		} else {
-			let min = core::cmp::min(buf.len(), guard.buffer.len());
-			let drained = guard.buffer.drain(..min).collect::<Vec<_>>();
-			buf[..min].copy_from_slice(drained.as_slice());
-			Ok(min)
-		}
+		Ok(UART_DEVICE.lock().buffer.read(buf)?)
 	}
 }
 
 impl ReadReady for SerialDevice {
 	fn read_ready(&mut self) -> Result<bool, Self::Error> {
-		let read_ready = !UART_DEVICE.lock().buffer.is_empty();
-		Ok(read_ready)
+		Ok(UART_DEVICE.lock().buffer.read_ready()?)
 	}
 }
 

src/errno.rs

@@ -1,5 +1,7 @@
 //! System error numbers.
 
+use core::convert::Infallible;
+
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 use thiserror::Error;
 
@@ -669,6 +671,12 @@ pub enum Errno {
 	Hwpoison = 133,
 }
 
+impl From<Infallible> for Errno {
+	fn from(value: Infallible) -> Self {
+		match value {}
+	}
+}
+
 /// Returns the pointer to `errno`.
 #[cfg(all(
 	not(any(feature = "common-os", feature = "nostd")),