From 9e304e21a1792033c6244e677dbe48c743c6be29 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pavel=20Kala=C5=A1=20=28Floxen=29?=
 <pavelkalas2048@seznam.cz>
Date: Sun, 12 Jul 2026 12:17:49 +0200
Subject: [PATCH] =?UTF-8?q?P=C5=99id=C3=A1n=20ovlada=C4=8D=20COM1:=20inici?=
 =?UTF-8?q?alizace=20UART=20a=20odes=C3=ADl=C3=A1n=C3=AD=20znak=C5=AF=20p?=
 =?UTF-8?q?=C5=99es=20s=C3=A9riov=C3=BD=20port?=
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---
 drivers/serial.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 drivers/serial.c

diff --git a/drivers/serial.c b/drivers/serial.c
new file mode 100644
index 0000000..a2933eb
--- /dev/null
+++ b/drivers/serial.c
@@ -0,0 +1,74 @@
+/*
+ * AsterOS Kernel
+ * COM1 serial driver for robust debugging output.
+ */
+
+#include "serial.h"
+
+#define COM1_PORT 0x3F8
+
+static int g_serial_ready = 0;
+
+static inline void outb(u16 port, u8 value) {
+    __asm__ volatile ("outb %0, %1" : : "a"(value), "Nd"(port));
+}
+
+static inline u8 inb(u16 port) {
+    u8 value;
+    __asm__ volatile ("inb %1, %0" : "=a"(value) : "Nd"(port));
+    return value;
+}
+
+int serial_is_ready(void) {
+    return g_serial_ready;
+}
+
+void serial_init(void) {
+    g_serial_ready = 0;
+
+    outb(COM1_PORT + 1, 0x00);
+    outb(COM1_PORT + 3, 0x80);
+    outb(COM1_PORT + 0, 0x03);
+    outb(COM1_PORT + 1, 0x00);
+    outb(COM1_PORT + 3, 0x03);
+    outb(COM1_PORT + 2, 0xC7);
+    outb(COM1_PORT + 4, 0x0B);
+
+    outb(COM1_PORT + 4, 0x1E);
+    outb(COM1_PORT + 0, 0xAE);
+    if (inb(COM1_PORT + 0) != 0xAE) {
+        return;
+    }
+
+    outb(COM1_PORT + 4, 0x0F);
+    g_serial_ready = 1;
+}
+
+void serial_write_char(char c) {
+    u32 spin;
+
+    if (!g_serial_ready) {
+        return;
+    }
+
+    if (c == '\n') {
+        serial_write_char('\r');
+    }
+
+    for (spin = 0; spin < 100000U; ++spin) {
+        if ((inb(COM1_PORT + 5) & 0x20U) != 0U) {
+            outb(COM1_PORT + 0, (u8)c);
+            return;
+        }
+    }
+}
+
+void serial_write_string(const char *text) {
+    if (!text) {
+        return;
+    }
+
+    while (*text) {
+        serial_write_char(*text++);
+    }
+}