From 52a22c4b18195dd777e1f0b9d22e2e6decca0bbe Mon Sep 17 00:00:00 2001
From: Ciro Santilli <ciro.santilli@gmail.com>
Date: Sat, 24 Aug 2019 00:00:01 +0000
Subject: [PATCH] serial: make awesome

---
 .gitignore                |  1 +
 Makefile                  |  1 +
 README.adoc               | 22 ++++++++++++++++++++++
 bios_hello_world_serial.S | 19 +++++++++++--------
 4 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/.gitignore b/.gitignore
index e10ebfd..8ec8d44 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,5 +6,6 @@
 *.o
 *.so
 *.tmp
+*.tmp.*
 /README.html
 tmp.S
diff --git a/Makefile b/Makefile
index 69ae0d0..1ec48c3 100644
--- a/Makefile
+++ b/Makefile
@@ -55,6 +55,7 @@ bochs: $(RUN_FILE)
 	CYLINDERS="$$(($$(stat -c '%s' '$(RUN_FILE)') / 512))" && \
 	bochs -qf /dev/null \
 		'ata0-master: type=disk, path="$(RUN_FILE)", mode=flat, cylinders='"$$CYLINDERS"', heads=1, spt=1' \
+		'com1: enabled=1, mode=file, dev=$(RUN).tmp.serial' \
 		'boot: disk' \
 		'display_library: sdl2' \
 		'megs: 128'
diff --git a/README.adoc b/README.adoc
index 7e29ec3..e7a2e90 100644
--- a/README.adoc
+++ b/README.adoc
@@ -68,6 +68,11 @@ Then on the terminal start the simulation with:
 c
 ....
 
+To quit Bochs either:
+
+* press the poweroff button inside its GUI
+* Ctrl + C on terminal and the type `quit` and hit enter
+
 TODO: automate this step.
 
 Bibliography: https://stackoverflow.com/questions/6142925/how-can-i-use-bochs-to-run-assembly-code/32871939#32871939
@@ -2164,6 +2169,23 @@ While it is possible to learn those topics as you go along, and it is almost cer
 
 === Serial UART
 
+TODO: get working on QEMU, working on Bochs:
+
+....
+./run bios_hello_world_serial bochs
+cat bios_hello_world_serial.tmp.serial
+....
+
+File content:
+
+....
+hello world
+....
+
+Source: link:bios_hello_world_serial.S[]
+
+Bibliography:
+
 * https://stackoverflow.com/questions/22571379/intel-galileo-bare-metal-uart
 * https://stackoverflow.com/questions/27594297/how-to-print-a-string-to-the-terminal-in-x86-64-assembly-nasm-without-syscall
 
diff --git a/bios_hello_world_serial.S b/bios_hello_world_serial.S
index 514f206..0764851 100644
--- a/bios_hello_world_serial.S
+++ b/bios_hello_world_serial.S
@@ -1,14 +1,17 @@
 #include "common.h"
 BEGIN
-    DBG
-   mov $0x00, %ah// Initialize COM port
-   mov $0xe3, %al// Initialization value
-   mov $0x00, %dx// Port number
-   int $0x14
-   mov $msg, %si
+    /* Initialize COM port. */
+    mov $0x00, %ah
+    /* Initialization value. */
+    mov $0xe3, %al
+    /* Port number. */
+    mov $0x00, %dx
+    int $0x14
+    mov $msg, %si
 loop:
     lodsb
-    mov $0x01, %ah//Send value 
+    /* Send value */
+    mov $0x01, %ah
     or %al, %al
     jz halt
     int $0x14
@@ -16,4 +19,4 @@ loop:
 halt:
     hlt
 msg:
-.asciz "hello World!\n"
+    .asciz "hello world\n"