h6. [[CDFS]] h6(. » [[CDFS Technical Details]] h6((. » CDFS Control Block h2. CDFS Control Block CDFS control blocks are used with most [[CDFS SWI Calls]] to identify the target drive. Control blocks are a five-word long, word-aligned data structure, and are typically constructed by zero-extending the fields contained in the compacted 32bit 'physical drive number' that is returned by [[CDFS_ConvertDriveToDevice]]. |_<^. Control Block |_<^. Physical Drive No. |_<^. Contents | |<^. Word 0 |<^. Bits 0-2 |<^. SCSI Device ( 0 - 7) | |<^. Word 1 |<^. Bits 3-4 |<^. SCSI Card (0 - 3) | |<^. Word 2 |<^. Bits 5-7 |<^. SCSI Logical Unit Number (0 - 7) | |<^. Word 3 |<^. Bits 8-15 |<^. Driver handle (0-255) (see [[CD_Identify]]) | |<^. Word 4 |<^. Bits 16-31 |<^. Reserved/extension field (0-65535) | h4. Notes Although the CD driver stack uses SCSI device identifiers to identify drives, the identifiers may not correspond to 'real' SCSI devices that are known to the [[SCSIDriver|SCSI stack]]. To send SCSI commands to drives, [[CD_SCSIUserOp]] should be used, rather than attempting to use [[SCSI_Op]] directly. h4. See also * [[CDFS SWI Calls]] * [[CDFS_ConvertDriveToDevice]]