sos-code-article10/drivers/x86_videomem.c

/* Copyright (C) 2004  David Decotigny

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
   USA.
*/
#include <sos/klibc.h>
#include <hwcore/ioports.h>

#include "x86_videomem.h"

/* The text video memory starts at address 0xB8000. Odd bytes are the
   ASCII value of the character, even bytes are attribute for the
   preceding character. */
#define VIDEO   0xb8000


/* Console screen size */
#define LINES   25
#define COLUMNS 80

/*
 * VGA ports and commands.
 * 
 * @see Ralf Brown's interrupt (and port) list	 
 * http://www-2.cs.cmu.edu/~ralf/files.html	 
 */

/* VGA ports */
#define VGA_COMMAND_PORT 0x3D4
#define VGA_DATA_PORT    0x3D5

/* VGA commands */
#define VGA_SET_CURSOR_START 0xA
#define VGA_SET_CURSOR_END   0xB
#define VGA_SET_CURSOR_HIGH  0xE
#define VGA_SET_CURSOR_LOW   0xF

/** The structure of a character element in the video memory. @see
    http://webster.cs.ucr.edu/AoA DOS edition chapter 23 */
typedef struct {
  unsigned char character;
  unsigned char attribute;
} __attribute__ ((packed)) x86_video_mem[LINES*COLUMNS];



/** The base pointer for the video memory */
static volatile x86_video_mem *video = (volatile x86_video_mem*)VIDEO;

sos_ret_t sos_x86_videomem_setup(void)
{
  /* CRT index port => ask for access to register 0xa ("cursor
     start") */
  outb(0x0a, VGA_COMMAND_PORT);

  /* (RBIL Tables 708 & 654) CRT Register 0xa => bit 5 = cursor OFF */
  outb(1 << 5, VGA_DATA_PORT);

  return SOS_OK;
}


sos_ret_t sos_x86_videomem_cls(unsigned char attribute)
{
  /* Clears the screen */
  int i;
  for(i = 0 ; i < LINES*COLUMNS ; i++)
    {
      (*video)[i].character = 0;
      (*video)[i].attribute = attribute;
    }

  return SOS_OK;
}


sos_ret_t sos_x86_videomem_putstring(unsigned char row, unsigned char col,
				     unsigned char attribute,
				     const char *str)
{
  unsigned video_offs = row*COLUMNS + col;

  if (video_offs >= LINES*COLUMNS)
    return -SOS_EINVAL;

  for ( ; str && *str && (video_offs < LINES*COLUMNS) ; str++, video_offs++)
    {
      (*video)[video_offs].character = (unsigned char)*str;
      (*video)[video_offs].attribute = attribute;
    }

  return SOS_OK;
}


sos_ret_t sos_x86_videomem_putchar(unsigned char row, unsigned char col,
				   unsigned char attribute,
				   unsigned char c)
{
  unsigned video_offs = row*COLUMNS + col;

  if (video_offs >= LINES*COLUMNS)
    return -SOS_EINVAL;

  (*video)[video_offs].character = c;
  (*video)[video_offs].attribute = attribute;

  return SOS_OK;
}


sos_ret_t sos_x86_videomem_printf(unsigned char row, unsigned char col,
				  unsigned char attribute,
				  const char *format, /* args */...)
{
  char buff[256];
  va_list ap;

  va_start(ap, format);
  vsnprintf(buff, sizeof(buff), format, ap);
  va_end(ap);

  return sos_x86_videomem_putstring(row, col, attribute, buff);
}


/*
 * Console that supports scrolling, based on the low-level code
 * above. This console only takes part of the screen, starting at row
 * CONSOLE_ROW_START. The rows before that one are free for use by the
 * kernel debugging messages.
 */

/* Current row in the high-level console. Must be signed, because of
   computations inside sos_screen_putchar() */
static int row;

/* Current column in the high-level console. Must be signed, because
   of computations inside sos_screen_putchar() */
static int col;

/* The limit between the low-level console, accessible to the kernel,
   and the high-level console, accessible to the user applications
   through the sos_screen_putchar() function. */
#define CONSOLE_ROW_START 12

static void sos_screen_set_cursor (unsigned int _row, unsigned int _col)
{
  unsigned int pos;

  pos = (_row * COLUMNS + _col);

  outb(VGA_SET_CURSOR_HIGH, VGA_COMMAND_PORT);
  outb( (pos >> 8), VGA_DATA_PORT);
  outb(VGA_SET_CURSOR_LOW, VGA_COMMAND_PORT);
  outb( (pos & 0xFF), VGA_DATA_PORT);
}

sos_ret_t sos_screen_putchar (char c)
{
  if (c == '\r')
    {
      /* Go to first row */
      col = 0;
    }

  /* New line */
  else if (c == '\n')
    {
      /* Go to next line */
      col = 0;
      row ++;
    }

  /* Remove the last character */
  else if (c == '\b')
    {
      /* Next character should be displayed instead of the current
	 one */
      col --;

      /* Handle the case where we're at the beginning of a line */
      if (col < 0)
	{
	  row --;
	  col = COLUMNS-1;

	  if (row < CONSOLE_ROW_START)
	    {
	      row = CONSOLE_ROW_START;
	      col = 0;
	    }
	}

      /* Replace the current character with a space */
      sos_x86_videomem_putchar
	(row, col, SOS_X86_VIDEO_FG_BLUE | SOS_X86_VIDEO_BG_LTGRAY, ' ');
    }
  else if (c != 0)
    {
      sos_x86_videomem_putchar
	(row, col, SOS_X86_VIDEO_FG_BLUE | SOS_X86_VIDEO_BG_LTGRAY, c);
      col++;
      if (col == COLUMNS)
	{
	  col = 0;
	  row++;
	}
    }

  /* Need to scroll ? */
  if (row == LINES)
    {
      int i;

      /* Copy each line in the previous line */
      for (i = CONSOLE_ROW_START; i < LINES; i++)
	memcpy ((char*) video + i * COLUMNS * 2,
		(char*) video + ((i + 1) * COLUMNS * 2),
		COLUMNS * 2);

      /* Reset the last line of the console */
      for (i = 0; i < COLUMNS; i++)
	sos_x86_videomem_putchar
	  (LINES-1, i, SOS_X86_VIDEO_FG_BLUE | SOS_X86_VIDEO_BG_LTGRAY, ' ');

      row--;
    }

  sos_screen_set_cursor (row, col);

  return SOS_OK;
}

sos_ret_t sos_screen_init (void)
{
  int i, j;

  row = CONSOLE_ROW_START;
  col = 0;

  /* Set the first scan line for the cursor, and the blinking
     mode. First scan line is 11, so that we have a visible
     cursor. */
  outb(VGA_SET_CURSOR_START, VGA_COMMAND_PORT);
  outb(((0x2 << 5) | 14), VGA_DATA_PORT);

  for (i = CONSOLE_ROW_START; i < LINES; i++)
    {
      for (j = 0; j < COLUMNS; j++)
	sos_x86_videomem_putchar
	  (i, j, SOS_X86_VIDEO_FG_BLUE | SOS_X86_VIDEO_BG_LTGRAY, ' ');
    }

  sos_screen_set_cursor (row, col);

  return SOS_OK;
}