draw.c

   1 #include <fcntl.h>
   2 #include <linux/fb.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <string.h>
   6 #include <sys/ioctl.h>
   7 #include <sys/mman.h>
   8 #include <unistd.h>
   9 #include "draw.h"
  10
  11 #define MIN(a, b)       ((a) < (b) ? (a) : (b))
  12 #define MAX(a, b)       ((a) > (b) ? (a) : (b))
  13 #define NLEVELS         (1 << 8)
  14
  15 static struct fb_var_screeninfo vinfo;  /* linux-specific FB structure */
  16 static struct fb_fix_screeninfo finfo;  /* linux-specific FB structure */
  17 static int fd;                          /* FB device file descriptor */
  18 static void *fb;                        /* mmap()ed FB memory */
  19 static int bpp;                         /* bytes per pixel */
  20 static int nr, ng, nb;                  /* color levels */
  21 static int rl, rr, gl, gr, bl, br;      /* shifts per color */
  22
  23 static int fb_len(void)
  24 {
  25         return finfo.line_length * vinfo.yres_virtual;
  26 }
  27
  28 static void fb_cmap_save(int save)
  29 {
  30         static unsigned short red[NLEVELS], green[NLEVELS], blue[NLEVELS];
  31         struct fb_cmap cmap;
  32         if (finfo.visual == FB_VISUAL_TRUECOLOR)
  33                 return;
  34         cmap.start = 0;
  35         cmap.len = MAX(nr, MAX(ng, nb));
  36         cmap.red = red;
  37         cmap.green = green;
  38         cmap.blue = blue;
  39         cmap.transp = NULL;
  40         ioctl(fd, save ? FBIOGETCMAP : FBIOPUTCMAP, &cmap);
  41 }
  42
  43 void fb_cmap(void)
  44 {
  45         unsigned short red[NLEVELS], green[NLEVELS], blue[NLEVELS];
  46         struct fb_cmap cmap;
  47         int i;
  48         if (finfo.visual == FB_VISUAL_TRUECOLOR)
  49                 return;
  50
  51         for (i = 0; i < nr; i++)
  52                 red[i] = (65535 / (nr - 1)) * i;
  53         for (i = 0; i < ng; i++)
  54                 green[i] = (65535 / (ng - 1)) * i;
  55         for (i = 0; i < nb; i++)
  56                 blue[i] = (65535 / (nb - 1)) * i;
  57
  58         cmap.start = 0;
  59         cmap.len = MAX(nr, MAX(ng, nb));
  60         cmap.red = red;
  61         cmap.green = green;
  62         cmap.blue = blue;
  63         cmap.transp = NULL;
  64
  65         ioctl(fd, FBIOPUTCMAP, &cmap);
  66 }
  67
  68 unsigned fb_mode(void)
  69 {
  70         return ((rl < gl) << 22) | ((rl < bl) << 21) | ((gl < bl) << 20) |
  71                 (bpp << 16) | (vinfo.red.length << 8) |
  72                 (vinfo.green.length << 4) | (vinfo.blue.length);
  73 }
  74
  75 static void init_colors(void)
  76 {
  77         nr = 1 << vinfo.red.length;
  78         ng = 1 << vinfo.blue.length;
  79         nb = 1 << vinfo.green.length;
  80         rr = 8 - vinfo.red.length;
  81         rl = vinfo.red.offset;
  82         gr = 8 - vinfo.green.length;
  83         gl = vinfo.green.offset;
  84         br = 8 - vinfo.blue.length;
  85         bl = vinfo.blue.offset;
  86 }
  87
  88 int fb_init(char *dev)
  89 {
  90         fd = open(dev, O_RDWR);
  91         if (fd < 0)
  92                 goto failed;
  93         if (ioctl(fd, FBIOGET_VSCREENINFO, &vinfo) < 0)
  94                 goto failed;
  95         if (ioctl(fd, FBIOGET_FSCREENINFO, &finfo) < 0)
  96                 goto failed;
  97         fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
  98         bpp = (vinfo.bits_per_pixel + 7) >> 3;
  99         fb = mmap(NULL, fb_len(), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
 100         if (fb == MAP_FAILED)
 101                 goto failed;
 102         init_colors();
 103         fb_cmap_save(1);
 104         fb_cmap();
 105         return 0;
 106 failed:
 107         perror("fb_init()");
 108         close(fd);
 109         return 1;
 110 }
 111
 112 void fb_free(void)
 113 {
 114         fb_cmap_save(0);
 115         munmap(fb, fb_len());
 116         close(fd);
 117 }
 118
 119 int fb_rows(void)
 120 {
 121         return vinfo.yres;
 122 }
 123
 124 int fb_cols(void)
 125 {
 126         return vinfo.xres;
 127 }
 128
 129 void *fb_mem(int r)
 130 {
 131         return fb + (r + vinfo.yoffset) * finfo.line_length + vinfo.xoffset * bpp;
 132 }
 133
 134 unsigned fb_val(int r, int g, int b)
 135 {
 136         return ((r >> rr) << rl) | ((g >> gr) << gl) | ((b >> br) << bl);
 137 }