int cdrom_get_last_written(struct cdrom_device_info *cdi, long *last_written)
{
	struct cdrom_tocentry toc;
	disc_information di;
	track_information ti;
	__u32 last_track;
	int ret = -1, ti_size;

	if (!CDROM_CAN(CDC_GENERIC_PACKET))
		goto use_toc;

	ret = cdrom_get_disc_info(cdi, &di);
	if (ret < (int)(offsetof(typeof(di), last_track_lsb)
			+ sizeof(di.last_track_lsb)))
		goto use_toc;

	/* if unit didn't return msb, it's zeroed by cdrom_get_disc_info */
	last_track = (di.last_track_msb << 8) | di.last_track_lsb;
	ti_size = cdrom_get_track_info(cdi, last_track, 1, &ti);
	if (ti_size < (int)offsetof(typeof(ti), track_start))
		goto use_toc;

	/* if this track is blank, try the previous. */
	if (ti.blank) {
		if (last_track == 1)
			goto use_toc;
		last_track--;
		ti_size = cdrom_get_track_info(cdi, last_track, 1, &ti);
	}

	if (ti_size < (int)(offsetof(typeof(ti), track_size)
				+ sizeof(ti.track_size)))
		goto use_toc;

	/* if last recorded field is valid, return it. */
	if (ti.lra_v && ti_size >= (int)(offsetof(typeof(ti), last_rec_address)
				+ sizeof(ti.last_rec_address))) {
		*last_written = be32_to_cpu(ti.last_rec_address);
	} else {
		/* make it up instead */
		*last_written = be32_to_cpu(ti.track_start) +
				be32_to_cpu(ti.track_size);
		if (ti.free_blocks)
			*last_written -= (be32_to_cpu(ti.free_blocks) + 7);
	}
	return 0;

	/* this is where we end up if the drive either can't do a
	   GPCMD_READ_DISC_INFO or GPCMD_READ_TRACK_RZONE_INFO or if
	   it doesn't give enough information or fails. then we return
	   the toc contents. */
use_toc:
	toc.cdte_format = CDROM_MSF;
	toc.cdte_track = CDROM_LEADOUT;
	if ((ret = cdi->ops->audio_ioctl(cdi, CDROMREADTOCENTRY, &toc)))
		return ret;
	sanitize_format(&toc.cdte_addr, &toc.cdte_format, CDROM_LBA);
	*last_written = toc.cdte_addr.lba;
	return 0;
}

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