W1_F2D_READ_MAXLEN
if (todo >= W1_F2D_READ_MAXLEN)
block_read = W1_F2D_READ_MAXLEN;
todo -= W1_F2D_READ_MAXLEN;
buf += W1_F2D_READ_MAXLEN;
off += W1_F2D_READ_MAXLEN;
u8 cmp[W1_F2D_READ_MAXLEN];