1#include <stdio.h>
2#include <stdlib.h>
3#include <string.h>
4#include <stdint.h>
5#include <sys/types.h>
6
7#include <unistd.h>
8#include <fcntl.h>
9#include <math.h>
10#include <time.h>
11#include <errno.h>
12
13#include <sys/resource.h>
14#include <sys/syscall.h>
15#include <sys/mman.h>
16
17#include <linux/fb.h>
18
19int64_t systemTime()
20{
21    struct timespec t;
22    t.tv_sec = t.tv_nsec = 0;
23    clock_gettime(CLOCK_MONOTONIC, &t);
24    return (int64_t)(t.tv_sec)*1000000000LL + t.tv_nsec;
25}
26
27int main(int argc, char** argv)
28{
29    char const * const device_template[] = {
30            "/dev/graphics/fb%u",
31            "/dev/fb%u",
32            0 };
33    int fd = -1;
34    int i=0;
35    int j=0;
36    char name[64];
37    while ((fd==-1) && device_template[i]) {
38        snprintf(name, 64, device_template[i], 0);
39        fd = open(name, O_RDWR, 0);
40        i++;
41    }
42    if (fd < 0)
43        return -errno;
44
45    struct fb_fix_screeninfo finfo;
46    if (ioctl(fd, FBIOGET_FSCREENINFO, &finfo) == -1)
47        return -errno;
48
49    struct fb_var_screeninfo info;
50    if (ioctl(fd, FBIOGET_VSCREENINFO, &info) == -1)
51        return -errno;
52
53    info.reserved[0] = 0;
54    info.reserved[1] = 0;
55    info.reserved[2] = 0;
56    info.xoffset = 0;
57    info.yoffset = 0;
58    info.bits_per_pixel = 16;
59    info.activate = FB_ACTIVATE_NOW;
60
61    if (ioctl(fd, FBIOPUT_VSCREENINFO, &info) == -1) {
62        printf("FBIOPUT_VSCREENINFO failed (%d x %d)\n",
63                info.xres_virtual, info.yres_virtual);
64        return 0;
65    }
66
67    if (ioctl(fd, FBIOGET_VSCREENINFO, &info) == -1)
68        return -errno;
69
70    uint64_t denominator = (uint64_t)( info.upper_margin + info.lower_margin + info.yres )
71                         * ( info.left_margin  + info.right_margin + info.xres )
72                         * info.pixclock;
73    int refreshRate = denominator ? (1000000000000000LLU / denominator) : 0;
74
75    float xdpi = (info.xres * 25.4f) / info.width;
76    float ydpi = (info.yres * 25.4f) / info.height;
77    float fps  = refreshRate / 1000.0f;
78
79    printf( "using (fd=%d)\n"
80            "id           = %s\n"
81            "xres         = %d px\n"
82            "yres         = %d px\n"
83            "xres_virtual = %d px\n"
84            "yres_virtual = %d px\n"
85            "bpp          = %d\n"
86            "r            = %2u:%u\n"
87            "g            = %2u:%u\n"
88            "b            = %2u:%u\n",
89                fd,
90                finfo.id,
91                info.xres,
92                info.yres,
93                info.xres_virtual,
94                info.yres_virtual,
95                info.bits_per_pixel,
96                info.red.offset, info.red.length,
97                info.green.offset, info.green.length,
98                info.blue.offset, info.blue.length
99        );
100
101    printf( "width        = %d mm (%f dpi)\n"
102            "height       = %d mm (%f dpi)\n"
103            "refresh rate = %.2f Hz\n",
104                info.width,  xdpi,
105                info.height, ydpi,
106                fps
107        );
108
109    printf("upper_margin=%d, lower_margin=%d, left_margin=%d, right_margin=%d, pixclock=%d, finfo.smem_len=%d\n",
110            info.upper_margin, info.lower_margin, info.left_margin, info.right_margin, info.pixclock, finfo.smem_len);
111
112    if (ioctl(fd, FBIOGET_FSCREENINFO, &finfo) == -1)
113        return -errno;
114
115    if (finfo.smem_len <= 0)
116        return -errno;
117
118    /*
119     * Open and map the display.
120     */
121
122    uint16_t* buffer  = (uint16_t*) mmap(
123            0, finfo.smem_len,
124            PROT_READ | PROT_WRITE,
125            MAP_SHARED,
126            fd, 0);
127
128    if (buffer == MAP_FAILED)
129        return -errno;
130
131    // at least for now, always clear the fb
132    memset(buffer, 0, finfo.smem_len);
133    memset(buffer, 0xff, 320*(info.yres_virtual/2)*2);
134
135    int l,t,w,h;
136    l=0;
137    t=0;
138    w=320;
139    h=480;
140    info.reserved[0] = 0x54445055; // "UPDT";
141    info.reserved[1] = (uint16_t)l | ((uint32_t)t << 16);
142    info.reserved[2] = (uint16_t)(l+w) | ((uint32_t)(t+h) << 16);
143
144    int err;
145    int c = 0;
146    int64_t time = systemTime();
147    while (1) {
148
149        info.activate = FB_ACTIVATE_VBL;
150        info.yoffset = 0;
151        ioctl(fd, FBIOPUT_VSCREENINFO, &info);
152
153        info.activate = FB_ACTIVATE_VBL;
154        info.yoffset = info.yres_virtual/2;
155        err = ioctl(fd, FBIOPUT_VSCREENINFO, &info);
156
157        c+=2;
158        if (c==60*2) {
159            int64_t now = systemTime();
160            time = now - time;
161            printf("refresh rate = %f Hz\n", (c*1000000000.0 / (double)time));
162            c = 0;
163            time = now;
164        }
165    }
166    return 0;
167}
168