From 7a7312022869c8bb1c038e3ce43b5c455db5e92c Mon Sep 17 00:00:00 2001
From: Kenneth J Davis <PerditionC@gmail.com>
Date: Sat, 10 Feb 2024 17:27:23 -0500
Subject: [PATCH] copy over debug print to COM ports from UNSTABLE branch

---
 kernel/console.asm | 51 ++++++++++++++++++++++++++++++++++++++++++++++
 kernel/prf.c       | 36 +++++++++++++++++++++++++++-----
 2 files changed, 82 insertions(+), 5 deletions(-)

diff --git a/kernel/console.asm b/kernel/console.asm
index 3a2beb5..4287fc3 100644
--- a/kernel/console.asm
+++ b/kernel/console.asm
@@ -57,6 +57,11 @@ uScanCode	db	0		; Scan code for con: device
 global          _kbdType
 _kbdType        db      0		; 00 for 84key, 10h for 102key        
 
+%IFDEF DEBUG_PRINT_COMPORT
+ASYNC_NEED_INIT     db      1
+%ENDIF
+
+
                 global  ConInit
 ConInit:
 	        xor	ax,ax
@@ -245,12 +250,58 @@ _int29_handler:
                 push    di
                 push    bp
                 push    bx
+%IFDEF DEBUG_PRINT_COMPORT
+                cmp     bx, 0xFD05              ; magic value for COM print routine
+                je      .comprint
+%ENDIF
                 mov     ah,0Eh
                 mov     bx,7
                 int     10h                     ; write char al, teletype mode
+.int29hndlr_ret:
                 pop     bx
                 pop     bp
                 pop     di
                 pop     si
                 pop     ax
                 iret
+%IFDEF DEBUG_PRINT_COMPORT
+.comprint:
+                push    dx
+                mov     dx, 1                   ; 0=COM1,1=COM2,2=COM3,3=COM4
+
+                mov     ah, [cs:ASYNC_NEED_INIT]
+                or      ah,ah
+                jz      .skip_init
+                push    ax                      ; preserve char (AL) to print
+
+                ; initialize serial port using BIOS to DOS default
+                ; of 2400 bps, 8 data bits, 1 stop bit, and no parity
+                mov     ax, 0x00A3
+                int     14h                     ; BIOS initialize serial port
+
+                mov     ax, 0x011B              ; clear the remote screen (ESC[2J)
+                int     14h                     ; BIOS write character to serial port
+                mov     ax, 0x015B              ; '['
+                int     14h                     ; BIOS write character to serial port
+                mov     ax, 0x0132              ; '2'
+                int     14h                     ; BIOS write character to serial port
+                mov     ax, 0x014A              ; 'J'
+                int     14h                     ; BIOS write character to serial port
+
+                ; mark initialization complete
+                mov     byte [cs:ASYNC_NEED_INIT], 0
+
+                pop     ax                      ; restore char to print
+.skip_init:
+                cmp     al, 0x0A                ; do we need to add a carriage return?
+                jne     .print_it
+                mov     ax, 0x010D              ; print as \r\n
+                int     14h
+                mov     al, 0x0A
+.print_it:
+                mov     ah, 0x01
+                int     14h                     ; BIOS write character to serial port
+
+                pop     dx
+                jmp     .int29hndlr_ret
+%ENDIF ; DEBUG_PRINT_COMPORT
diff --git a/kernel/prf.c b/kernel/prf.c
index 3bfddb9..71dbacf 100644
--- a/kernel/prf.c
+++ b/kernel/prf.c
@@ -100,6 +100,13 @@ void put_console(int c)
 #ifdef __WATCOMC__
 void int29(char c);
 #pragma aux int29 = "int 0x29" parm [al] modify exact [bx];
+
+#ifdef DEBUG_PRINT_COMPORT
+void fastComPrint(char c);
+#pragma aux fastComPrint = \
+      "mov bx, 0xFD05" \
+      "int 0x29" parm [al] modify exact [bx];
+#endif
 #endif
 
 void put_console(int c)
@@ -115,6 +122,9 @@ void put_console(int c)
   __int__(0x29);
 #elif defined(__WATCOMC__)
   int29(c);
+#if defined DEBUG_PRINT_COMPORT
+  fastComPrint(c);
+#endif
 #elif defined(__GNUC__)
   asm volatile("int $0x29" : : "a"(c) : "bx");
 #elif defined(I86)
@@ -157,6 +167,11 @@ STATIC VOID handle_char(COUNT c)
   if (charp == 0)
     put_console(c);
   else
+#ifdef DEBUG_PRINT_COMPORT
+  if (charp == (BYTE SSFAR *)-1)
+    fastComPrint(c);
+  else
+#endif
     *charp++ = c;
 }
 
@@ -237,13 +252,24 @@ int VA_CDECL sprintf(char * buff, CONST char * fmt, ...)
   return 0;
 }
 
+#ifdef DEBUG_PRINT_COMPORT
+int dbgc_printf(CONST char * fmt, ...)
+{
+  va_list arg;
+
+  va_start(arg, fmt);
+  charp = (BYTE SSFAR *)-1;
+  do_printf(fmt, arg);
+  handle_char('\0');
+  return 0;
+}
+#endif
+
 STATIC void do_printf(CONST BYTE * fmt, va_list arg)
 {
-  int base;
-  BYTE s[11];
-  BYTE FAR * p;
-  int size;
-  unsigned char flags;
+  int base, size;
+  BYTE s[13]; /* long enough for a 32-bit octal number string with sign */
+  BYTE flags, FAR *p;
 
   for (;*fmt != '\0'; fmt++)
   {