Archipelago » qemu

        /* MMC writing cannot be done via pread/pwrite, because it sometimes

         * involves writing beyond the maximum LBA or to negative LBA (lead-in).

         * And once you do these writes, reading from the block device is

         * unreliable, too.  It is even possible that reads deliver random data

         * from the host page cache (this is probably a Linux bug).

         *

         * We might use scsi_disk_reqops as long as no writing commands are

         * seen, but performance usually isn't paramount on optical media.  So,

         * just make scsi-block operate the same as scsi-generic for them.

         */

        if (s->qdev.type != TYPE_ROM) {

            return scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun,

                                  hba_private);

        }