[Linux-fbdev-devel] Re: Linux-fbdev-devel digest, Vol 1 #197 - 5 msgs

[<chr...@ph...>]

Hello,

Your driver uses PSEUDOCOLOR, so it uses a palette. You have to store the colors (red, green, blue) in your palette (usually palette contains 256 colors=2^8 ) and then to store the color number (a byte) in the framebuffer memory.

For using a such palette, look at fbtest.c below  (written by James Simmons AFAIK)
Hope it will help you...

Cut here:
------------------------------------
/*
* fbtest.c
*
* build: gcc fbtest.c -o fbtest
*/


#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/ioctl.h>
#include <sys/mman.h>


int init(void);
void clear(void);
int setrgb(int, int, int, int);


unsigned char *vmem;
int fd = -1;
int buffer_size;


static u_int16_t red[256], blue[256], green[256], transp[256];


static struct fb_cmap pal;


int init(void)
{
struct fb_var_screeninfo info;


if ((fd = open("/dev/fb0", O_RDWR)) == -1)
{
fprintf(stderr, "cannot open framebuffer device (%s)\n",
strerror(errno));
return -1;
}


if (ioctl(fd, FBIOGET_VSCREENINFO, &info))
{
fprintf(stderr, "ioctl failed on framebuffer device (%s)\n",
strerror(errno));
close(fd);
return -1;
}


/* we're only going to try 8-bit pixels: */


if (info.bits_per_pixel == 8)
buffer_size = info.xres * info.yres;
else
{
fprintf(stderr, "we don't do % bits per pixel mode\n",
info.bits_per_pixel);
close(fd);
return -1;
}


if ((vmem = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0)) == MAP_FAILED)
{
fprintf(stderr, "cannot mmap() framebuffer device (%s)\n",
strerror(errno));
close(fd);
return -1;
}


pal.start = 0;
pal.len = 256;
pal.red = red;
pal.green = green;
pal.blue = blue;
pal.transp = transp;


if (ioctl(fd, FBIOGETCMAP, &pal))
{
fprintf(stderr, "couldn't get cmap\n");
close(fd);
return -1;
}


return 0;
}


void clear(void)
{
memset(vmem, 0, buffer_size);
}


int setrgb(int n, int r, int g, int b)
{
pal.red[n] = r << 8;
pal.green[n] = g << 8;
pal.blue[n] = b << 8;
pal.transp[n] = 0;


return ioctl(fd, FBIOPUTCMAP, &pal);
}


int main(int argc, char **argv)
{
if (!init())
{
setrgb(0, 255, 0, 0);
clear();
}


return 0;
}
------------------------------------------





hi

i'm new to framebuffer development. i want to write a small library for
my embedded system(MPC823L) with a lcd(SHARP LQ64D341). i use the
framebufferdriver(lcd823.c) from the denx.de kernel tree.

my problem now is to get control over the colors. i use this to open the
framebuffer:

int fbfd = 0;
long int screensize = 0;
unsigned char *fbp = 0;
struct fb_fix_screeninfo finfo;
struct fb_var_screeninfo vinfo;

...

fbfd = open("/dev/fb", O_RDWR);
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
fbp = (unsigned char*)mmap(0, screensize, PROT_READ | PROT_WRITE,
                    MAP_SHARED, fbfd, 0);


to set a pixel i use something like this:

setPixel(int x, int y, int color){
     long int location;
     location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8)                          + (y+vinfo.yoffset) * finfo.line_length;                          *(fbp
+ location) = color;
     }
}

but what is the structure of the var color(should the type be unsigned
char?)? what is red, green and blue?
i know that the driver uses pseudocolor and 8bit per pixel.

thanks for helping

stefan