+/* There are so many devices that report the capacity incorrectly,
+ * this routine was written to counteract some of the resulting
+ * problems.
+ */
+static void last_sector_hacks(struct us_data *us, struct scsi_cmnd *srb)
+{
+ struct gendisk *disk;
+ struct scsi_disk *sdkp;
+ u32 sector;
+
+ /* To Report "Medium Error: Record Not Found */
+ static unsigned char record_not_found[18] = {
+ [0] = 0x70, /* current error */
+ [2] = MEDIUM_ERROR, /* = 0x03 */
+ [7] = 0x0a, /* additional length */
+ [12] = 0x14 /* Record Not Found */
+ };
+
+ /* If last-sector problems can't occur, whether because the
+ * capacity was already decremented or because the device is
+ * known to report the correct capacity, then we don't need
+ * to do anything.
+ */
+ if (!us->use_last_sector_hacks)
+ return;
+
+ /* Was this command a READ(10) or a WRITE(10)? */
+ if (srb->cmnd[0] != READ_10 && srb->cmnd[0] != WRITE_10)
+ goto done;
+
+ /* Did this command access the last sector? */
+ sector = (srb->cmnd[2] << 24) | (srb->cmnd[3] << 16) |
+ (srb->cmnd[4] << 8) | (srb->cmnd[5]);
+ disk = srb->request->rq_disk;
+ if (!disk)
+ goto done;
+ sdkp = scsi_disk(disk);
+ if (!sdkp)
+ goto done;
+ if (sector + 1 != sdkp->capacity)
+ goto done;
+
+ if (srb->result == SAM_STAT_GOOD && scsi_get_resid(srb) == 0) {
+
+ /* The command succeeded. If the capacity is odd
+ * (i.e., if the sector number is even) then the
+ * "always-even" heuristic would be wrong for this
+ * device. Issue a WARN() so that the kerneloops.org
+ * project will be notified and we will then know to
+ * mark the device with a CAPACITY_OK flag. Hopefully
+ * this will occur for only a few devices.
+ *
+ * Use the sign of us->last_sector_hacks to tell whether
+ * the warning has already been issued; we don't need
+ * more than one warning per device.
+ */
+ if (!(sector & 1) && us->use_last_sector_hacks > 0) {
+ unsigned vid = le16_to_cpu(
+ us->pusb_dev->descriptor.idVendor);
+ unsigned pid = le16_to_cpu(
+ us->pusb_dev->descriptor.idProduct);
+ unsigned rev = le16_to_cpu(
+ us->pusb_dev->descriptor.bcdDevice);
+
+ WARN(1, "%s: Successful last sector success at %u, "
+ "device %04x:%04x:%04x\n",
+ sdkp->disk->disk_name, sector,
+ vid, pid, rev);
+ us->use_last_sector_hacks = -1;
+ }
+
+ } else {
+ /* The command failed. Allow up to 3 retries in case this
+ * is some normal sort of failure. After that, assume the
+ * capacity is wrong and we're trying to access the sector
+ * beyond the end. Replace the result code and sense data
+ * with values that will cause the SCSI core to fail the
+ * command immediately, instead of going into an infinite
+ * (or even just a very long) retry loop.
+ */
+ if (++us->last_sector_retries < 3)
+ return;
+ srb->result = SAM_STAT_CHECK_CONDITION;
+ memcpy(srb->sense_buffer, record_not_found,
+ sizeof(record_not_found));
+
+ /* In theory we might want to issue a WARN() here if the
+ * capacity is even, since it could indicate the device
+ * has the READ CAPACITY bug _and_ the real capacity is
+ * odd. But it could also indicate that the device
+ * simply can't access its last sector, a failure mode
+ * which is surprisingly common. So no warning.
+ */
+ }
+
+ done:
+ /* Don't reset the retry counter for TEST UNIT READY commands,
+ * because they get issued after device resets which might be
+ * caused by a failed last-sector access.
+ */
+ if (srb->cmnd[0] != TEST_UNIT_READY)
+ us->last_sector_retries = 0;
+}
+