From 2c79240cc66dd2a116056662def9bdc165b2b3e7 Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Sun, 14 May 2017 11:06:13 +0200
Subject: playing with addresses and seing the CRT index port number now in
 port8_read

---
 README       |  9 ++++++++-
 src/kernel.c |  5 +----
 src/port.asm | 21 ++++++++++++++++++++-
 src/port.c   |  5 -----
 src/vga.c    | 34 +++++++++++++++++++++++++++++++---
 5 files changed, 60 insertions(+), 14 deletions(-)

diff --git a/README b/README
index 0d29dbd..c92d044 100644
--- a/README
+++ b/README
@@ -14,7 +14,7 @@ ndisasm -b16 -o7c00h -a image.bin | less
 objdump -M intel -d kernel.o | less
 
 gcc -m32 -ffreestanding -c -o kernel.o kernel.c
-ld -o kernel.bin -Ttext 0x8000 kernel.o -m elf_i386 --oformat binary
+ld -o kernel.bin -Ttext 0x8400 kernel.o -m elf_i386 --oformat binary
 objdump -M intel -d kernel.bin | less
 
 # oformat: objdump -i lists tons of formats
@@ -37,6 +37,13 @@ Booting from 0000:7c00
 Next at t=14040244
 (0) [0x000000007c00] 0000:7c00 (unk. ctxt): mov ax, 0x0000            ; b80000
 
+C entry:
+break 0x8400
+
+disassemble kernel in 32-bit mode
+ndisasm -b32 -o8400h -a kernel.bin | less
+
+
 links
 -----
 
diff --git a/src/kernel.c b/src/kernel.c
index 91ed26b..d5db426 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -27,10 +27,7 @@ void entry( void )
 	}
 	vga_put_char_at( &vga, x_pos, y_pos, '.' );	
 	vga_put_newline( &vga );
-	
-	vga_put_hex( &vga, 4711 );
-	vga_put_newline( &vga );
-
+   
 	//~ vga_set_color( &vga, VGA_COLOR_WHITE );
 	//~ vga_set_background_color( &vga, VGA_COLOR_RED );
 	//~ vga_clear_screen( &vga );
diff --git a/src/port.asm b/src/port.asm
index 34d1f78..c7a2b85 100644
--- a/src/port.asm
+++ b/src/port.asm
@@ -1,18 +1,33 @@
 [bits 32]
 
 global port8_write
+global port8_read
 
+; void port8_write( port8_t *port, uint8_t data );
 port8_write:
+	push ebp
+	mov ebp, esp
 	mov edx, [ebp+16] 
 	mov eax, (edx)
+;	mov eax, [epb+8]
 ;	mov dx, [ebp+8]
 ;	out ax, dl
+	leave
 	ret
 
-
+; uint8_t port8_read( port8_t *port )
+port8_read:
+	push ebp
+	mov ebp, esp
+	mov edx, [ebp+8]
+	mov eax, [edx]
+	leave
+	ret
+	
 ;~ void port8_init( port8_t *port, uint16_t number )
 
 	
+;                    __asm__ volatile("inb %1, %0" : "=a" (result) : "Nd" (_port));
 
 ;~ global _myfunc 
 ;~ _myfunc:  push ebp 
@@ -23,3 +38,7 @@ port8_write:
           ;~ leave                  ; mov esp,ebp / pop ebp 
           ;~ ret
           ;    __asm__ volatile("outb %0, %1" : : "a" (_data), "Nd" (_port));
+
+;~ {
+	;~ return 0;
+;~ }
diff --git a/src/port.c b/src/port.c
index 1a55669..f64cc69 100644
--- a/src/port.c
+++ b/src/port.c
@@ -4,8 +4,3 @@ void port8_init( port8_t *port, uint16_t number )
 {
 	port->number = number;
 }
-
-uint8_t port8_read( port8_t *port )
-{
-	return 0;
-}
diff --git a/src/vga.c b/src/vga.c
index 0c344f7..fd67552 100644
--- a/src/vga.c
+++ b/src/vga.c
@@ -53,12 +53,41 @@ void vga_set_cursor( vga_t *vga, const int x, const int y )
 
 void vga_set_cursor_from_hardware( vga_t *vga )
 {
+	// value of port we want to see later in assembly
+	uint16_t n = vga->crtc_index_port.number;
+	vga_put_hex( vga, n );
+	vga_put_newline( vga );
+	
+	// the address of the vga structure
+	uintptr_t uip = (uintptr_t)( (void *)vga );
+	vga_put_hex( vga, uip );
+	vga_put_newline( vga );
+
+	// the address of the port structure inside the vga structure
+	uintptr_t uip2 = (uintptr_t)( (void *)&vga->crtc_index_port );
+	vga_put_hex( vga, uip2 );
+	vga_put_newline( vga );
+
+	// the address of the number membger in the port structure inside the vga structure
+	// must be the same as uip2 by C99
+	uintptr_t uip3 = (uintptr_t)( (void *)&vga->crtc_index_port.number );
+	vga_put_hex( vga, uip3 );
+	vga_put_newline( vga );
+	
+	uint8_t data = port8_read( &(vga->crtc_index_port ) );
+	vga_put_hex( vga, data );
+	vga_put_newline( vga );
+//~ unsigned short offset;
+   //~ out(0x3D4, 14);
+   //~ offset = in(0x3D5) << 8;
+   //~ out(0x3D4, 15);
+   //~ offset |= in(0x3D5);	
 }
 
 void vga_set_cursor_on_hardware( vga_t *vga )
 {
     uint16_t hw_cursor_pos = vga->cursor_x + vga->cursor_y * vga->res_x;
-    
+
     port8_write( &vga->crtc_index_port, 15 );
     port8_write( &vga->crtc_index_port, hw_cursor_pos & 0xff );
     port8_write( &vga->crtc_index_port, 14 );
@@ -164,8 +193,7 @@ void vga_put_hex( vga_t *vga, const uint32_t v )
 {
 	char buf[9];
 	
-	strlcpy( buf, "0x", 9 );
-	vga_put_string( vga, (const char *)buf );
+	vga_put_string( vga, "0x" );
 	itoa( v, (char *)buf, 16 );
 	vga_put_string( vga, (const char *)buf );
 }
-- 
cgit v1.2.3-54-g00ecf