armsoc_driver.c

drmModeResPtr res;
drmModeCrtcPtr crtc;
drmModeFBPtr fb;
struct drm_mode_map_dumb mreq;
int ret;
uint8_t *map;
size_t size;
unsigned int i, j, off;
uint8_t r, g, b;

FILE *file = fopen("/root/LOG", "a");

res = drmModeGetResources(pARMSOC->drmFD);
crtc = drmModeGetCrtc(pARMSOC->drmFD, res->crtcs[0]);
fb = drmModeGetFB(pARMSOC->drmFD, crtc->buffer_id);

fprintf(file, "crtc->buffer_id: %d, fb->handle: %d\n", crtc->buffer_id, fb->handle);

memset(&mreq, 0, sizeof(mreq));
mreq.handle = fb->handle;
ret = drmIoctl(pARMSOC->drmFD, DRM_IOCTL_MODE_MAP_DUMB, &mreq);
if (ret) {
	fprintf(file, "error in drmIoctl\n");
}

size = fb->pitch * fb->height;

map = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, pARMSOC->drmFD, mreq.offset);
if (map == MAP_FAILED) {
	fprintf(file, "error in mmap\n");
}

srand(time(NULL));

memset(map, 0, size);

for (j = 0; j < fb->height; j++) {
	for (i = 0; i < fb->width; i++) {

		r = rand() % 0xff;
		g = rand() % 0xff;
		b = rand() % 0xff;

		off = fb->pitch * j + i * 4;
		*(uint32_t *)&map[off] = (r << 16) | (g << 8) | b;
	}
}


fclose(file);	
drmModeFreeCrtc(crtc);
drmModeFreeResources(res);