summaryrefslogtreecommitdiffstats
path: root/doc/framebuffer-howto.doc
blob: e37c22b2a28109c726a4f682353d89531c49643d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
/****************************************************************************
**
** Windowsystem-specific pages
**
** Copyright (C) 2000-2008 Trolltech ASA.  All rights reserved.
**
** This file is part of the Qt GUI Toolkit.
**
** This file may be used under the terms of the GNU General
** Public License versions 2.0 or 3.0 as published by the Free
** Software Foundation and appearing in the files LICENSE.GPL2
** and LICENSE.GPL3 included in the packaging of this file.
** Alternatively you may (at your option) use any later version
** of the GNU General Public License if such license has been
** publicly approved by Trolltech ASA (or its successors, if any)
** and the KDE Free Qt Foundation.
**
** Please review the following information to ensure GNU General
** Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** This file may be used under the terms of the Q Public License as
** defined by Trolltech ASA and appearing in the file LICENSE.QPL
** included in the packaging of this file.  Licensees holding valid Qt
** Commercial licenses may use this file in accordance with the Qt
** Commercial License Agreement provided with the Software.
**
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
** herein.
**
**********************************************************************/

/*!
\page emb-framebuffer-howto.html

\title Enabling the Linux Framebuffer

This is only a short guide.
See \l file:/usr/src/linux/README and
\l file:/usr/src/linux/Documentation/fb/ for detailed information.
There is also a detailed explanation at
\l http://www.linuxdoc.org/HOWTO/Framebuffer-HOWTO.html.

\list 1
\i Make sure that you have the Linux kernel source code in
\l file:/usr/src/linux/.

\i Log in as root and \c cd \c /usr/src/linux

\i Configure the kernel:
   
   Run:
\code
    make menuconfig
\endcode

   Select "Code maturity level options" and set "Prompt for
   development and/or incomplete code/drivers".

   Then select "Console drivers" and set "Support for frame buffer
   devices" to built-in (even if it says EXPERIMENTAL). Then configure
   the driver. Most modern graphics cards can use the "VESA VGA
   graphics console"; use that or a driver that specifically matches
   your video card. Finally, enable "Advanced low level driver options"
   and make sure that 16 and 32 bpp packed pixel support are enabled. 

   When you are finished, chose exit and save.

\i Compile the kernel

   First do:
\code
    make dep
\endcode
   then:
\code
    make bzImage
\endcode

  The new kernel should now be in arch/i386/boot/bzImage.

\i Copy the kernel to the boot directory:
\code
    cp arch/i386/boot/bzImage /boot/linux.vesafb
\endcode

\i Edit /etc/lilo.conf.

  \warning Keep a backup of \l file:/etc/lilo.conf, and have a rescue disk
  available. If you make a mistake, the machine may not boot.

   The file \l file:/etc/lilo.conf specifies how the system boots. The
   precise contents of the file varies from system to system. Here is
   an example:
\code
# LILO configuration file
boot = /dev/hda3
delay = 30 
image = /boot/vmlinuz
  root = /dev/hda3
  label = Linux
  read-only # Non-UMSDOS filesystems should be mounted read-only for checking
other=/dev/hda1
	label=nt
	table=/dev/hda
\endcode

  Make a new "image" section that is a copy of the first one, but with
\code
  image = /boot/linux.vesafb 
\endcode
  and 
\code
  label = Linux-vesafb
\endcode
  Place it just above the first image section.

  Add a line before the image section saying \c{vga = 791}. (Meaning
  1024x768, 16 bpp.) 

  With the above example, lilo.conf would now be:
\code
# LILO configuration file
boot = /dev/hda3
delay = 30 
vga = 791
image = /boot/linux.vesafb
  root = /dev/hda3
  label = Linux-vesafb
  read-only # Non-UMSDOS filesystems should be mounted read-only for checking
image = /boot/vmlinuz
  root = /dev/hda3
  label = Linux
  read-only # Non-UMSDOS filesystems should be mounted read-only for checking
other=/dev/hda1
	label=nt
	table=/dev/hda
\endcode

Do not change any existing lines in the file; just add new ones.

\i To make the new changes take effect, run the lilo program:
\code
    lilo
\endcode

\i Reboot the system. You should now see a penguin logo while the
   system is booting.
   (Or more than one on a multi-processor machine.)

\i If it does not boot properly with the new kernel, you can boot with
   the old kernel by entering the label of the old image section at
   the LILO prompt. (with the example lilo.conf file, the old label is
   Linux.)

   If that does not work (probably because of an error in lilo.conf),
   boot the machine using your rescue disk, restore \l
   file:/etc/lilo.conf from backup and re-run lilo.

\i Testing: Here's a short program that opens the frame buffer and draws a
   gradient-filled red square.

\code
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>

int main()
{
    int fbfd = 0;
    struct fb_var_screeninfo vinfo;
    struct fb_fix_screeninfo finfo;
    long int screensize = 0;
    char *fbp = 0;
    int x = 0, y = 0;
    long int location = 0;

    // Open the file for reading and writing
    fbfd = open("/dev/fb0", O_RDWR);
    if (!fbfd) {
	printf("Error: cannot open framebuffer device.\n");
	exit(1);
    }
    printf("The framebuffer device was opened successfully.\n");

    // Get fixed screen information
    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
	printf("Error reading fixed information.\n");
	exit(2);
    }

    // Get variable screen information
    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
	printf("Error reading variable information.\n");
	exit(3);
    }

    printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel );

    // Figure out the size of the screen in bytes
    screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;

    // Map the device to memory
    fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
		       fbfd, 0);
    if ((int)fbp == -1) {
	printf("Error: failed to map framebuffer device to memory.\n");
	exit(4);
    }
    printf("The framebuffer device was mapped to memory successfully.\n");

    x = 100; y = 100;       // Where we are going to put the pixel

    // Figure out where in memory to put the pixel
    for ( y = 100; y < 300; y++ )
	for ( x = 100; x < 300; x++ ) {

	    location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
		       (y+vinfo.yoffset) * finfo.line_length;

	    if ( vinfo.bits_per_pixel == 32 ) {
		*(fbp + location) = 100;        // Some blue
		*(fbp + location + 1) = 15+(x-100)/2;     // A little green
		*(fbp + location + 2) = 200-(y-100)/5;    // A lot of red
		*(fbp + location + 3) = 0;      // No transparency
	    } else  { //assume 16bpp
		int b = 10;
		int g = (x-100)/6;     // A little green
		int r = 31-(y-100)/16;    // A lot of red
		unsigned short int t = r<<11 | g << 5 | b;
		*((unsigned short int*)(fbp + location)) = t;
	    }

	}
    munmap(fbp, screensize);
    close(fbfd);
    return 0;
}
\endcode
\endlist

*/