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The serial UART driver (serial-uart-16550) attaches to the first serial port (COM1) at I/O base address 0x3F8 and mirrors every byte of kernel output to the wire. Any text written to the VGA display — shell command output, kernel log messages, and kernel panic output — is also sent through serial_put so you can capture a complete runtime transcript without a monitor. This makes the serial driver especially useful when running MVH Kernel under QEMU or other emulators where a physical display is inconvenient.

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What Gets Mirrored

The serial driver receives every character the kernel emits, with no filtering or buffering delay. This includes:
  • All interactive shell output (ls, cat, cpuinfo, lspci, dmesg, and every other command)
  • The structured kernel log ring (viewable live, not just via dmesg)
  • Kernel panic output: panic code, exception details, register dump, and stack trace
  • The kernel boot sequence messages
The serial port is write-only from the kernel’s perspective in the current release — the driver does not implement serial input. All user input is handled exclusively by the PS/2 keyboard driver.

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Using Serial Output with QEMU

QEMU routes COM1 serial output to whatever backend you specify with the -serial flag. Two common workflows: Capture output to a log file:
Stream output to your terminal (stdio):
When you use -serial stdio, QEMU mixes serial output with its own console. If you want clean separation, use -nographic together with -serial stdio to redirect the entire session:

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Port and Baud Rate

The driver initializes the 16550 UART at boot via serial_init(), configures the baud rate divisor, enables the FIFO, and sets the line control register for 8N1 framing before the shell becomes interactive.

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API Reference

The serial driver exposes two functions from include/mvh/serial.h:
Both functions are called internally by the kernel’s output layer — you do not need to call them directly unless you are extending the kernel.

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Driver ID

The device manager registers this driver under the ID serial-uart-16550. Run devices in the shell to confirm it is online.