kfs: added the serial print

* 38400 bauds
* 1 stop bit
* no parity check
* 8 bits words

Signed-off-by: Olivier Gayot <duskcoder@gmail.com>

5 files changed, 118 insertions, 29 deletions

diff --git a/src/main.c b/src/main.c
index 68fdb66..4ea0449 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,9 +1,5 @@
-#define NB_COLS 80
-#define NB_ROWS 25
-#define BPC     2
-#define BPR     (BPC * NB_COLS)
-
-#define VIDEO_BUFFER 0xB8000
+#include "serial.h"
+#include "vga.h"
 
 /* XXX doest not always handle memory overlaps */
 static void my_memmove(void *_dest, const void *_src, int n)
@@ -16,21 +12,12 @@ static void my_memmove(void *_dest, const void *_src, int n)
     }
 }
 
-static void my_memset(void *_dest, int c, int n)
-{
-    char *dest = _dest;
-
-    for (int i = 0; i < n; ++i) {
-        dest[i] = c;
-    }
-}
-
 static void clear_line(void *_addr)
 {
     char *addr = _addr;
 
-    for (int i = 0; i < NB_COLS; ++i) {
-        if (i % BPC == 0) {
+    for (int i = 0; i < VGA_COLS; ++i) {
+        if (i % VGA_BPC == 0) {
             *addr++ = ' ';
         } else {
             *addr++ = 0x7;
@@ -40,33 +27,33 @@ static void clear_line(void *_addr)
 
 int printk(const char *str)
 {
-    static const long int offset = VIDEO_BUFFER;
-    static char *addr = (char *) VIDEO_BUFFER;
+    static const long int offset = VGA_BASE;
+    static char *addr = (char *) VGA_BASE;
     int count = 0;
 
     for (int i = 0; str[i]; ++i) {
-        /* TODO add the serial port handling */
+        serial_putchar(str[i]);
 
         char chr;
         char *new_addr = addr;
-        char *addr_line = (char *)(((long)(addr - offset) / BPR) * BPR) + offset;
+        char *addr_line = (char *)(((long)(addr - offset) / VGA_BPR) *
+                VGA_BPR) + offset;
 
-        if ((long)addr >= offset + NB_ROWS * BPR) {
+        if ((long)addr >= offset + VGA_ROWS * VGA_BPR) {
             /* shift up */
-            addr -= BPR;
-            addr_line -= BPR;
-            my_memmove((void *)offset, (void *)offset + BPR, BPR * (NB_ROWS - 1));
-            clear_line(addr_line);
+            addr -= VGA_BPR;
+            addr_line -= VGA_BPR;
+            my_memmove((void *)offset, (void *)offset + VGA_BPR, VGA_BPR
+                    * (VGA_ROWS - 1)); clear_line(addr_line);
         }
 
-
         switch (str[i]) {
             case '\n':
-                new_addr = addr_line + BPR;
+                new_addr = addr_line + VGA_BPR;
                 chr = '\0';
                 break;
             default:
-                new_addr = addr + BPC;
+                new_addr = addr + VGA_BPC;
                 chr = str[i];
                 break;
         }
@@ -83,4 +70,7 @@ int printk(const char *str)
 
 int main(void)
 {
+    serial_init();
+
+    return 0;
 }
diff --git a/src/serial.c b/src/serial.c
new file mode 100644
index 0000000..720d454
--- /dev/null
+++ b/src/serial.c
@@ -0,0 +1,57 @@
+#define COM1_BASE 0x3f8
+#define COM2_BASE 0x2f8
+#define COM3_BASE 0x3e8
+#define COM4_BASE 0x2e8
+
+#include "uart_16550.h"
+
+static inline void outb(unsigned char value, unsigned short port)
+{
+    asm volatile("outb %0,%1" : : "a" (value), "dN" (port));
+}
+
+static inline unsigned char inb(unsigned short port)
+{
+    unsigned char value;
+
+    asm volatile("inb %1,%0" : "=a" (value) : "dN" (port));
+
+    return value;
+}
+
+int serial_putchar(unsigned char c)
+{
+    outb(c, COM1_BASE);
+
+    return 1;
+}
+
+int serial_init(void)
+{
+    /* set the communication parameters */
+    unsigned char lcr_value = 0x0;
+
+    lcr_value = DATA_WORD_LEN_8
+        | STOP_BIT_1
+        | PARITY_NONE
+        | BREAK_SIGNAL_DISABLED
+        | DLAB_ACCESSIBLE_DLL_DLM;
+
+    outb(lcr_value, COM1_BASE + 3);
+
+    unsigned char dll_value = 0x03;
+    unsigned char dlm_value = 0x00;
+
+    outb(dll_value, COM1_BASE + 0);
+    outb(dlm_value, COM1_BASE + 1);
+
+    lcr_value = DATA_WORD_LEN_8
+        | STOP_BIT_1
+        | PARITY_NONE
+        | BREAK_SIGNAL_DISABLED
+        | DLAB_ACCESSIBLE_RBR_THR_IER;
+
+    outb(lcr_value, COM1_BASE + 3);
+
+    return 0;
+}
diff --git a/src/serial.h b/src/serial.h
new file mode 100644
index 0000000..da70b03
--- /dev/null
+++ b/src/serial.h
@@ -0,0 +1,7 @@
+#ifndef SERIAL_H
+#define SERIAL_H
+
+int serial_putchar(unsigned char c);
+int serial_init(void);
+
+#endif /* SERIAL_H */
diff --git a/src/uart_16550.h b/src/uart_16550.h
new file mode 100644
index 0000000..2e20eff
--- /dev/null
+++ b/src/uart_16550.h
@@ -0,0 +1,24 @@
+#ifndef UART_16550_H
+#define UART_16550_H
+
+#define DATA_WORD_LEN_5  0b00
+#define DATA_WORD_LEN_6  0b01
+#define DATA_WORD_LEN_7  0b10
+#define DATA_WORD_LEN_8  0b11
+
+#define STOP_BIT_1  0b000
+#define STOP_BIT_2  0b100 /* 1.5 stop bits for 5 bits words */
+
+#define PARITY_NONE 0b000000
+#define PARITY_ODD  0b001000
+#define PARITY_EVEN 0b011000
+#define PARITY_HIGH 0b101000
+#define PARITY_LOW  0b111000
+
+#define BREAK_SIGNAL_DISABLED   0b0000000
+#define BREAK_SIGNAL_ENABLED    0b1000000
+
+#define DLAB_ACCESSIBLE_RBR_THR_IER 0b00000000
+#define DLAB_ACCESSIBLE_DLL_DLM     0b10000000
+
+#endif /* UART_16550_H */
diff --git a/src/vga.h b/src/vga.h
new file mode 100644
index 0000000..a8f41ba
--- /dev/null
+++ b/src/vga.h
@@ -0,0 +1,11 @@
+#ifndef VGA_H
+#define VGA_H
+
+#define VGA_BASE    0xB8000
+
+#define VGA_COLS    80
+#define VGA_ROWS    25
+#define VGA_BPC     2
+#define VGA_BPR     (VGA_BPC * VGA_COLS)
+
+#endif /* VGA_H */