From 1606184551a422bca968f62102335fb1af4c4a73 Mon Sep 17 00:00:00 2001
From: Masato Imai <mii@sfc.wide.ad.jp>
Date: Sun, 24 Aug 2025 12:24:53 +0000
Subject: [PATCH] Serial I/O buffer #2

---
 nel_os_kernel/src/serial.rs              | 12 +++++++
 nel_os_kernel/src/vmm/x86_64/intel/io.rs | 41 +++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/nel_os_kernel/src/serial.rs b/nel_os_kernel/src/serial.rs
index 5ee848b..f886916 100644
--- a/nel_os_kernel/src/serial.rs
+++ b/nel_os_kernel/src/serial.rs
@@ -56,6 +56,18 @@ pub fn write_byte(byte: u8) {
     });
 }
 
+#[inline(always)]
+pub fn write_bytes(bytes: &[u8]) {
+    use x86_64::instructions::interrupts;
+
+    interrupts::without_interrupts(|| {
+        let mut serial = SERIAL1.lock();
+        for &b in bytes {
+            serial.send(b);
+        }
+    });
+}
+
 #[macro_export]
 macro_rules! print {
     ($($arg:tt)*) => {
diff --git a/nel_os_kernel/src/vmm/x86_64/intel/io.rs b/nel_os_kernel/src/vmm/x86_64/intel/io.rs
index 3e7884f..c8f2432 100644
--- a/nel_os_kernel/src/vmm/x86_64/intel/io.rs
+++ b/nel_os_kernel/src/vmm/x86_64/intel/io.rs
@@ -61,6 +61,7 @@ pub struct Pic {
     pub primary_read_sel: ReadSel,
     pub secondary_read_sel: ReadSel,
     pub serial: Serial,
+    pub serial_buffer: SerialBuffer,
 }
 
 impl Pic {
@@ -79,6 +80,7 @@ impl Pic {
             primary_read_sel: ReadSel::Irr,
             secondary_read_sel: ReadSel::Irr,
             serial: Serial::default(),
+            serial_buffer: SerialBuffer::default(),
         }
     }
 
@@ -235,7 +237,17 @@ impl Pic {
 
     fn handle_serial_out(&mut self, regs: &mut GuestRegisters, qual: QualIo) {
         match qual.port() {
-            0x3F8 => serial::write_byte(regs.rax as u8),
+            0x3F8 => {
+                let byte = regs.rax as u8;
+                if self.serial_buffer.end < self.serial_buffer.buffer.len() {
+                    self.serial_buffer.buffer[self.serial_buffer.end] = byte;
+                    self.serial_buffer.end += 1;
+                }
+
+                if byte == b'\n' || self.serial_buffer.end == self.serial_buffer.buffer.len() {
+                    self.serial_buffer.flush();
+                }
+            }
             0x3F9 => self.serial.ier = regs.rax as u8,
             0x3FA => {}
             0x3FB => {}
@@ -406,3 +418,30 @@ impl IOBitmap {
         }
     }
 }
+
+#[derive(Debug, Clone, Copy)]
+pub struct SerialBuffer {
+    pub buffer: [u8; 1024],
+    pub end: usize,
+}
+
+impl SerialBuffer {
+    pub fn flush(&mut self) {
+        if self.end == 0 {
+            return;
+        }
+
+        serial::write_bytes(&self.buffer[..self.end]);
+
+        self.end = 0;
+    }
+}
+
+impl Default for SerialBuffer {
+    fn default() -> Self {
+        Self {
+            buffer: [0; 1024],
+            end: 0,
+        }
+    }
+}