test

arch/x86_64/serial.c

@@ -0,0 +1,47 @@
+#include <zinnia/console.h>
+#include <stdint.h>
+#include <x86_64/asm.h>
+
+constexpr uint16_t COM1_BASE = 0x3F8;
+
+static bool is_ready() {
+    return asm_inb(COM1_BASE + 5) & 0x20;
+}
+
+static void serial_write(struct console* con, const char* buf, size_t count) {
+    for (size_t i = 0; i < count; i++) {
+        while (!is_ready())
+            asm volatile("pause");
+
+        asm_outb(COM1_BASE, buf[i]);
+    }
+}
+
+bool serial_setup(struct console* con) {
+    asm_outb(COM1_BASE + 1, 0x00); // Disable interrupts
+    asm_outb(COM1_BASE + 3, 0x80); // Enable DLAB (set baud rate divisor)
+    asm_outb(COM1_BASE, 0x01);     // Set divisor low byte (115200 baud if 1)
+    asm_outb(COM1_BASE + 1, 0x00); // Set divisor high byte
+    asm_outb(COM1_BASE + 3, 0x03); // 8 bits, no parity, one stop bit (8n1)
+    asm_outb(COM1_BASE + 2, 0xC7); // Enable FIFO, clear them, with 14-byte threshold
+    asm_outb(COM1_BASE + 4, 0x0B); // IRQs enabled, RTS/DSR set
+
+    asm_outb(COM1_BASE + 4, 0x1E); // Set to loopback mode.
+    asm_outb(COM1_BASE, 0xAE);     // Send a test byte.
+
+    // If we don't get the same value back, this serial port doesn't work.
+    if (asm_inb(COM1_BASE) != 0xAE) {
+        return false;
+    }
+
+    asm_outb(COM1_BASE + 4, 0x0F); // Disable loopback mode.
+
+    return true;
+}
+
+static struct console serial_con = {
+    .name = "com1",
+    .write = serial_write,
+    .init = serial_setup,
+};
+DEFINE_CONSOLE(&serial_con);