/* fbtool — fb0 helper: pan <yoffs> | blank <0|4> | copy | status.
 * Used to seed the double-buffer bug condition and clean up /dev/fb0.
 * ioctls: GETV 0x4600, GETFIX 0x4602, PAN 0x4606, BLANK 0x4611.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <errno.h>
#include <stdint.h>

#define GETV 0x4600
#define GETFIX 0x4602
#define PAN 0x4606
#define BLANK 0x4611

static int set_blank(int fd, int bl) {
    errno = 0;
    int r = ioctl(fd, BLANK, bl);
    printf("blank(%d) r=%d errno=%d\n", bl, r, errno);
    return r;
}
static int set_pan(int fd, int yoff) {
    unsigned char v[160]; memset(v,0,sizeof v);
    if (ioctl(fd, GETV, v) < 0) { perror("getvar"); return -1; }
    *(uint32_t*)(v+16)=0; *(uint32_t*)(v+20)=(uint32_t)yoff;
    errno = 0;
    int r = ioctl(fd, PAN, v);
    unsigned char w[160]; memset(w,0,sizeof w);
    ioctl(fd, GETV, w);
    printf("pan(%u) r=%d errno=%d yoffset now=%u\n", yoff, r, errno, *(uint32_t*)(w+20));
    return r;
}
static int do_copy(int fd) {
    unsigned char v[160]; memset(v,0,sizeof v);
    if (ioctl(fd, GETV, v) < 0) { perror("getvar"); return -1; }
    uint32_t yres=*(uint32_t*)(v+4), yv=*(uint32_t*)(v+12), bpp=*(uint32_t*)(v+24);
    unsigned char f[68]; memset(f,0,sizeof f);
    if (ioctl(fd, GETFIX, f) < 0) { perror("getfix"); return -1; }
    uint32_t line = *(uint32_t*)(f+44); if (!line) line = yres*(bpp/8);
    if (yv < yres) { printf("not double-buffered\n"); return -1; }
    size_t frame = (size_t)line * yres;
    unsigned char *p = mmap(NULL, frame*2, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    if (p == MAP_FAILED) { perror("mmap"); return -1; }
    memcpy(p+frame, p, frame);
    munmap(p, frame*2);
    printf("copy buffer0 -> buffer1 (%zu bytes)\n", frame);
    return 0;
}
int main(int argc, char **argv) {
    if (argc < 2) { fprintf(stderr,"usage: fbtool {blank 0|4} | {pan N} | {copy}\n"); return 2; }
    int fd = open("/dev/fb0", O_RDWR);
    if (fd < 0) { perror("open"); return 1; }
    int r = 0;
    if (!strcmp(argv[1],"blank") && argc>2) r = set_blank(fd, atoi(argv[2]));
    else if (!strcmp(argv[1],"pan") && argc>2) r = set_pan(fd, atoi(argv[2]));
    else if (!strcmp(argv[1],"copy")) r = do_copy(fd);
    else fprintf(stderr,"unknown cmd\n"), r=2;
    close(fd);
    return r<0?1:0;
}