One of the most basic SCSI commands is the INQUIRY command, used
to identify the type and make of the device. Here is the definition
from the SCSI-2 specification (for details refer to the SCSI-2
standard).
Table 44: INQUIRY Command
+=====-========-========-========-========-========-========-========-========+
| Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|Byte | | | | | | | | |
|=====+=======================================================================|
| 0 | Operation Code (12h) |
|-----+-----------------------------------------------------------------------|
| 1 | Logical Unit Number | Reserved | EVPD |
|-----+-----------------------------------------------------------------------|
| 2 | Page Code |
|-----+-----------------------------------------------------------------------|
| 3 | Reserved |
|-----+-----------------------------------------------------------------------|
| 4 | Allocation Length |
|-----+-----------------------------------------------------------------------|
| 5 | Control |
+=============================================================================+
The output data are as follows:
Table 45: Standard INQUIRY Data Format
+=====-========-========-========-========-========-========-========-========+
| Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|Byte | | | | | | | | |
|=====+==========================+============================================|
| 0 | Peripheral Qualifier | Peripheral Device Type |
|-----+-----------------------------------------------------------------------|
| 1 | RMB | Device-Type Modifier |
|-----+-----------------------------------------------------------------------|
| 2 | ISO Version | ECMA Version | ANSI-Approved Version |
|-----+-----------------+-----------------------------------------------------|
| 3 | AENC | TrmIOP | Reserved | Response Data Format |
|-----+-----------------------------------------------------------------------|
| 4 | Additional Length (n-4) |
|-----+-----------------------------------------------------------------------|
| 5 | Reserved |
|-----+-----------------------------------------------------------------------|
| 6 | Reserved |
|-----+-----------------------------------------------------------------------|
| 7 | RelAdr | WBus32 | WBus16 | Sync | Linked |Reserved| CmdQue | SftRe |
|-----+-----------------------------------------------------------------------|
| 8 | (MSB) |
|- - -+--- Vendor Identification ---|
| 15 | (LSB) |
|-----+-----------------------------------------------------------------------|
| 16 | (MSB) |
|- - -+--- Product Identification ---|
| 31 | (LSB) |
|-----+-----------------------------------------------------------------------|
| 32 | (MSB) |
|- - -+--- Product Revision Level ---|
| 35 | (LSB) |
|-----+-----------------------------------------------------------------------|
| 36 | |
|- - -+--- Vendor Specific ---|
| 55 | |
|-----+-----------------------------------------------------------------------|
| 56 | |
|- - -+--- Reserved ---|
| 95 | |
|=====+=======================================================================|
| | Vendor-Specific Parameters |
|=====+=======================================================================|
| 96 | |
|- - -+--- Vendor Specific ---|
| n | |
+=============================================================================+
The next example uses the low-level function handle_SCSI_cmd to
perform the Inquiry SCSI command.
We first append the command block to the generic header, then call
handle_SCSI_cmd. Note that the output buffer size argument for
the handle_SCSI_cmd call excludes the generic header size.
After command completion the output buffer contains the requested
data, unless an error occurred.
#define INQUIRY_CMD 0x12
#define INQUIRY_CMDLEN 6
#define INQUIRY_REPLY_LEN 96
#define INQUIRY_VENDOR 8 /* Offset in reply data to vendor name */
/* request vendor brand and model */
static unsigned char *Inquiry ( void )
{
unsigned char Inqbuffer[ SCSI_OFF + INQUIRY_REPLY_LEN ];
unsigned char cmdblk [ INQUIRY_CMDLEN ] =
{ INQUIRY_CMD, /* command */
0, /* lun/reserved */
0, /* page code */
0, /* reserved */
INQUIRY_REPLY_LEN, /* allocation length */
0 };/* reserved/flag/link */
memcpy( cmd + SCSI_OFF, cmdblk, sizeof(cmdblk) );
if (handle_SCSI_cmd(sizeof(cmdblk), 0, cmd,
sizeof(Inqbuffer) - SCSI_OFF, Inqbuffer )) {
fprintf( stderr, "Inquiry failed\n" );
exit(2);
}
return (Inqbuffer + SCSI_OFF);
}
The example above follows this structure. The Inquiry function copies
its command block behind the generic header (given by
SCSI_OFF). Input data is not present for this command.
Handle_SCSI_cmd will define the header structure. We can now
implement the function main to complete this working example
program.
void main( void )
{
fd = open(DEVICE, O_RDWR);
if (fd < 0) {
fprintf( stderr, "No access to "DEVICE".\n" );
exit(1);
}
/* print the result of Inquiry */
printf( "%s\n", Inquiry() + INQUIRY_VENDOR );
}
We first open the device, check for errors, and then call the higher level subroutine. Then we print the results in human readable format including the vendor, product, and revision.
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