From ef72082b2df5da98de13bbc8c35b66d891bd4b78 Mon Sep 17 00:00:00 2001
From: Benji Dial <Benji3.141@gmail.com>
Date: Thu, 26 Dec 2019 14:04:41 -0500
Subject: serial ports, echo vga output over COM2

---
 src/kernel/serial.asm | 71 ++++++++++++++++++++++++++++++++++++++++++++++-----
 src/kernel/serial.h   |  3 ---
 src/kernel/vga.c      |  2 +-
 3 files changed, 66 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/kernel/serial.asm b/src/kernel/serial.asm
index 9ebf84c..9077d99 100644
--- a/src/kernel/serial.asm
+++ b/src/kernel/serial.asm
@@ -18,12 +18,71 @@
 global send_byte
 global read_byte
 
-section .text
-;COM1:   COM2:   COM3:   COM4:
-;0x03f8, 0x02f8, 0x03e8, 0x02e8
-
 send_byte:;void send_byte(uint8_t value, uint8_t port)
-  ;TODO
+  push ebp
+  mov ebp, esp
+
+  mov cl, byte [ebp + 8] ;value
+  xor edx, edx
+  mov dl, byte [ebp + 12];port
+
+  test dl, 0xfc
+  jnz .leave
+
+  xchg ebx, edx
+  shl bl, 1
+  mov ax, word [ebx + com_ports]
+  mov ebx, edx
+  mov dx, ax
+
+  or dx, 5
+
+.check_ready:
+  in al, dx
+  test al, 0x20
+  jz .check_ready
+
+  and dx, 0xfff8
+
+  mov al, cl
+  out dx, al
+
+.leave:
+  leave
+  ret
 
 read_byte:;uint8_t read_byte(uint8_t port)
-  ;TODO
\ No newline at end of file
+  push ebp
+  mov ebp, esp
+
+  xor eax, eax
+
+  xor edx, edx
+  mov dl, byte [ebp + 8];port
+
+  test dl, 0xfc
+  jnz .leave
+
+  xchg ebx, edx
+  shl bl, 1
+  mov cx, word [ebx + com_ports]
+  mov ebx, edx
+  mov dx, cx
+
+  or dx, 5
+
+.check_ready:
+  in al, dx
+  test al, 0x01
+  jz .check_ready
+
+  and dx, 0xfff8
+
+  in al, dx
+
+.leave:
+  leave
+  ret
+
+section .rodata
+com_ports dw 0x03f8, 0x02f8, 0x03e8, 0x02e8
\ No newline at end of file
diff --git a/src/kernel/serial.h b/src/kernel/serial.h
index d5e4038..88d3712 100644
--- a/src/kernel/serial.h
+++ b/src/kernel/serial.h
@@ -29,10 +29,7 @@ enum serials {
   COM4 = 3
 };
 
-/*
-Commenting out so I don't accidentally call garbage while these are unimplemented.
 void send_byte(uint8_t value, uint8_t port);
 uint8_t read_byte(uint8_t port);
-*/
 
 #endif
\ No newline at end of file
diff --git a/src/kernel/vga.c b/src/kernel/vga.c
index 3d8de43..78da721 100644
--- a/src/kernel/vga.c
+++ b/src/kernel/vga.c
@@ -43,7 +43,7 @@ void scroll(void) {
 }
 
 void put_char(uint8_t ch) {
-  //send_byte(ch, COM2);
+  send_byte(ch, COM2);
   switch (ch) {
   case '\b':
     if (cursor_pos)
-- 
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