GENERAL_CTL
status = vid_blk_read_byte(dev, GENERAL_CTL, &gen_ctrl);
status = vid_blk_write_byte(dev, GENERAL_CTL, gen_ctrl);
status = vid_blk_read_byte(dev, GENERAL_CTL, &gen_ctrl);
status = vid_blk_write_byte(dev, GENERAL_CTL, gen_ctrl);