Document revision date: 30 March 2001 | |
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The VAXstation 2000 and MicroVAX 2000 disk driver supports some DSA disk operation. In particular, the driver supports block revectoring and bad block replacement. This provides the system with a logically perfect disk medium.
Like other DSA disks, if a serious error occurs during a replacement operation, the disk is write-locked to prevent further changes. This is done to preserve data integrity and minimize damage that could be caused by failing hardware. Unlike other DSA disks, there is no visible indication on the drive itself that the disk is write-locked. However, the following indicators help you determine that the disk has become write-protected:
If the disk becomes write-locked, you should use the following procedure:
If errors occurring during replacement operations persist, call Compaq
Customer Services.
2.2.13 SCSI Disk Class Driver
The VAXstation 3100, 3520, and 3540 contain a SCSI bus that provides access to as many as seven SCSI disks. The SCSI disk class driver controls SCSI disks on all of the above systems. Although, SCSI disks do not conform to DSA, they do support the following error recovery features:
All SCSI disks supplied by Compaq implement the REASSIGN BLOCKS command, which relocates data for a specific logical block to a different physical location on the disk. The SCSI disk class driver reassigns the block in the following instances: (1) when the retry threshold is exceeded during an attempt to read or write a block of data on the disk or (2) when an irrecoverable error occurs during a write operation.
Unlike DSA, there is no forced error flag in SCSI. Blocks that produce
irrecoverable errors during read operations are not reassigned in order
to prevent undetected loss of user data. Instead, the SCSI disk class
driver returns the SS$_PARITY status whenever a read operation results
in an irrecoverable error.
2.2.14 Audio Extensions to the SCSI Disk Class Driver
This section describes SCSI disk class driver audio commands and the $QIO interface by which the operating system provides audio functionality to the SCSI disk.
Table 2-1 lists the SCSI audio commands supported by the SCSI disk class driver.
Command | Audio Function Code1 | Description |
---|---|---|
Play Audio MSF | AUDIO_PLAY_AUDIO_MSF (5) | Requests the CD-ROM to begin an audio playback operation. The two required command arguments specify absolute starting and ending addresses of the playback in terms of minutes, seconds, and frame (MSF). |
Play Audio Track | AUDIO_PLAY_AUDIO_TRACK (6) | Requests the CD-ROM to begin an audio playback operation. The two required command arguments specify the starting and ending tracks of the playback in terms of track number and index. |
Play Audio | AUDIO_PLAY_AUDIO (4) | Requests the CD-ROM to begin an audio playback operation. The two required command arguments specify the starting logical block address (LBA) and the transfer count, in blocks, of the playback. |
Pause | AUDIO_PAUSE (0) | Requests the CD-ROM to suspend any active audio operations. In response, the CD-ROM enters the hold-track state, muting the audio output after playing the current block. |
Resume | AUDIO_RESUME (1) | Requests the CD-ROM to resume any active audio operations. In response, the CD-ROM exits the hold-track state and resumes playback at the block following the last block played. |
Get Status | AUDIO_GET_STATUS (9) | Requests from the CD-ROM the status of the currently active playback operation, as well as the state of the current block. The Get Status command corresponds to the SCSI II Read Sub-channel command (READ SUBQ) |
Set Volume | AUDIO_SET_VOLUME (11) | Requests the CD-ROM to adjust the output channel selection and volume settings for ports 0 through 3. The Set Volume command corresponds to the SCSI II Mode Select command for the CD-ROM Audio Control Parameters page. |
Get Volume | AUDIO_GET_VOLUME (12) | Requests from the CD-ROM the output channel selection and volume settings for ports 0 through 3. The Get Volume command corresponds to the SCSI II Mode Sense command for the CD-ROM Audio Control Parameters page. |
Prevent Removal | AUDIO_PREVENT_REMOVAL (2) | Prevents the removal of the CD caddy from the CD-ROM drive. |
Allow Removal | AUDIO_ALLOW_REMOVAL (3) | Allows the removal of the CD caddy from the CD-ROM drive. |
Get TOC | AUDIO_GET_TOC (10) | Requests from the CD-ROM a list of each track on the disk, including information about the audio or data contents of each track. Applications that require a detailed knowledge of the organization of a CD-ROM can use this function to obtain that information. The Get TOC command corresponds to the SCSI II Read TOC command. |
To employ the audio functions of the RRD42 CD-ROM reader, the application program issues a call to the $QIO system service using the following format:
status=SYS$QIO ([efn] ,[chan] ,func [,iosb] [,astadr] [,astprm]
[,p1] [,p2] [,p3] [,p4] [,p5] [,p6])
These arguments apply to the $QIO system service completion, not to device interrupt actions. For an explanation of these arguments, refer to the description of the $QIO system service in the OpenVMS System Services Reference Manual.
- [efn]
- [chan]
- [iosb]
- [astadr]
- [astprm]
func
The IO$_AUDIO function code allows the SCSI disk class driver to process SCSI audio commands.p1
Address of an audio control block (AUCB). The $QIO system service passes a SCSI audio command and command-specific control information to the SCSI disk class driver in the AUCB structure (see Section 2.2.14.2).p2
Size of the AUCB.
An application program that issues a call to the $QIO system service that specifies the IO$_AUDIO function code in the func argument must supply the address of an AUCB structure in the p1 argument and its size in the p2 argument.
An AUCB defines a specific SCSI audio command and provides the SCSI disk class driver with command-specific arguments and control information. Table 2-2 defines the fields that appear in an AUCB; these fields are shown in Figure 2-3. See SYS$EXAMPLES:CDROM_AUDIO.C for a code example that shows how an AUCB is defined in the C programming language.
Figure 2-3 Audio Control Block (AUCB)
Field | Use | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Audio Function Code | Numeric or symbolic code representing the audio function desired by the application program. (See Table 2-1.) The application program must provide a valid audio function code for each operation. | ||||||||||||||||
AUCB Version Number | Version of the AUCB and SCSI disk class driver audio interface. For the current version of the interface the value of this field should be 1. This field must never contain a zero. | ||||||||||||||||
Argument 1 |
This field is audio command-specific and contains the first argument of
the function as follows:
|
||||||||||||||||
Argument 2 |
This field is audio command-specific and contains the second argument
of the function as follows:
|
||||||||||||||||
Reserved | Must be zero. | ||||||||||||||||
Destination Buffer Address | Address of the application program's buffer from which the status from a GET_STATUS or GET_TOC function is returned. | ||||||||||||||||
Destination Buffer Count | Size, in bytes, of the destination buffer specified in the Destination Buffer Address field. For the GET_STATUS function, this field must contain the value 48 to receive complete status information. For the GET_TOC function, this field must contain the value 804 to receive full status. The SCSI disk class driver truncates the status data, if the destination buffer size is smaller than the size of the data. | ||||||||||||||||
Destination Buffer Transfer Count |
The SCSI disk class driver returns to this field the actual number of
bytes transferred to the buffer specified in the Destination Buffer
Address field.
Before accessing data returned by the GET_TOC or GET_STATUS commands, an application program must check the contents of this field to determine precisely how many bytes were returned by the CD-ROM. The application program initializes this field to zero. |
||||||||||||||||
Operating System Command Status |
Completion status of the SCSI audio function. This value is also
returned in the I/O status block of specified in the
iosb argument to the $QIO system service call. See
Table 2-3 for a description of these status codes.
The application program initializes this field to zero. |
||||||||||||||||
SCSI Command Status (optional) |
SCSI status of the current operation. The SCSI disk class driver
returns the SCSI status byte for the SCSI audio command described by
this AUCB in the low byte of the low-order word of this field. It
returns the sense key in the low byte of the high-order word. Refer to
the SCSI specification for information regarding SCSI status and SCSI
sense keys.
The application program initializes this field to zero. |
||||||||||||||||
Sense Data Buffer Address (optional) | Address of buffer to which the SCSI disk class driver returns sense data when errors occur during audio function execution. When this field is specified, in the event of a check condition on an Audio command, the SCSI disk class driver automatically issues a Request Sense command to retrieve the Sense Key/Sense Data from the target. The target returns this data to the buffer specified in this field before the failing $QIO audio function completes. | ||||||||||||||||
Sense Data Buffer Count (optional) | Size, in bytes, of the buffer specified in the Sense Data Buffer Address field. During request sense processing, the target device truncates the sense data to fit in this buffer. | ||||||||||||||||
Sense Data Buffer Transfer Count (optional) |
Actual number of bytes of sense data returned to the application in the
buffer specified in the Sense Data Buffer Address field.
The application program initializes this field to zero. |
||||||||||||||||
Reserved | Must be zero. |
The output channel selection and volume settings for CD-ROM ports as used by the SET_VOLUME function appear as shown in Figure 2-4.
Figure 2-4 Output Channel Selection and Volume Settings for CD-ROM Ports as Used by the SET_VOLUME Function
As indicated in Table 2-2, the AUCB provides for three levels of error status reporting:
If the CD-ROM device is currently software-enabled (that is, the volume has been mounted) and a unit attention is detected, then mount verification will be initiated by the driver. However, if the CD-ROM is not software-enabled, the event will simply be returned to the application issuing the Audio $QIO function.
SS$_NORMAL | AUCB command completed successfully. |
SS$_ABORT | Returned by the SCSI disk port driver. In general, you should retry commands that fail with this status. |
SS$_BADPARM | The driver detected an illegal value or missing value in the AUCB. |
SS$_CTRLERR | CD-ROM failed some part of its initialization sequence. When this status is returned, it is unlikely that the CD-ROM is usable. |
SS$_DEVOFFLINE | Device returned a not-ready sense key or failed the TEST UNIT READY/START sequence. |
SS$_DRVERR | CD-ROM failed to execute the command, either because the drive has failed or an illegal command was issued. Such a command could be a command that requested the drive to issue an audio command to a data track or attempted to perform a play operation on nonexistent tracks. |
SS$_ILLIOFUNC | Illegal I/O function was specified in the func argument of the $QIO request. |
SS$_IVADDR | Specified block number is larger than UCB$L_MAXBLOCK. |
SS$_MEDOFL | Last command failed because the drive detected the removal and replacement of the CD carrier, or the unsuccessful completion of a Request Sense command after a check condition error. In general, you should not retry commands that fail with this status. |
SS$_NOPRIV | Caller does not have sufficient privileges to execute this function. If the CD-ROM has not been mounted before an IO$_READVBLK function is issued, this status may be returned. |
SS$_OPINCOMPL | Number of bytes requested is less than the number of bytes returned. |
SS$_PARITY | Nonrecoverable media error (does not apply to audio functions). |
SS$_RECOVERR | Recovered media error (does not apply to audio functions). |
SS$_VOLINV | CD-ROM has not been mounted. |
SS$_WRITLCK | Write operations not permitted on read-only devices. |
To make effective use of mixed data and audio CDs, an application program requires detailed knowledge of the particular CD being played. The application program must know which tracks include data and which tracks include audio so it can use commands appropriate to the different track types. Issuing an audio command on a data track results in the command failing with a status of SS$_DRVERR.
By default, the SCSI disk class driver transfers all requests issued to
a CD-ROM in blocks of 512 bytes. This byte amount is referred to as the
default block size. Before attempting to issue READ operations to the
CD-ROM, you must ensure that the CD-ROM has been mounted as foreign or
as a Files-11 volume. The application program can then determine, by
issuing a GET_TOC function, which tracks (and, therefore, which logical
blocks) contain data and which contain audio information.
2.2.14.5 Programming Audio Applications
The following list contains information useful in avoiding problems when writing code using the SCSI audio interfaces:
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