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24. Example programs
Here is the C example program, which requests manufacturer/model and reports if a medium is loaded in the device.
#define DEVICE "/dev/sgc"
/* Example program to demonstrate the generic SCSI interface */
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <scsi/sg.h>
#define SCSI_OFF sizeof(struct sg_header)
static unsigned char cmd[SCSI_OFF + 18]; /* SCSI command buffer */
int fd; /* SCSI device/file descriptor */
/* process a complete scsi cmd. Use the generic scsi interface. */
static int handle_scsi_cmd(unsigned cmd_len, /* command length */
unsigned in_size, /* input data size */
unsigned char *i_buff, /* input buffer */
unsigned out_size, /* output data size */
unsigned char *o_buff /* output buffer */
)
{
int status = 0;
struct sg_header *sg_hd;
/* safety checks */
if (!cmd_len) return -1; /* need a cmd_len != 0 */
if (!i_buff) return -1; /* need an input buffer != NULL */
#ifdef SG_BIG_BUFF
if (SCSI_OFF + cmd_len + in_size > SG_BIG_BUFF) return -1;
if (SCSI_OFF + out_size > SG_BIG_BUFF) return -1;
#else
if (SCSI_OFF + cmd_len + in_size > 4096) return -1;
if (SCSI_OFF + out_size > 4096) return -1;
#endif
if (!o_buff) out_size = 0;
/* generic scsi device header construction */
sg_hd = (struct sg_header *) i_buff;
sg_hd->reply_len = SCSI_OFF + out_size;
sg_hd->twelve_byte = cmd_len == 12;
sg_hd->result = 0;
#if 0
sg_hd->pack_len = SCSI_OFF + cmd_len + in_size; /* not necessary */
sg_hd->pack_id; /* not used */
sg_hd->other_flags; /* not used */
#endif
/* send command */
status = write( fd, i_buff, SCSI_OFF + cmd_len + in_size );
if ( status < 0 || status != SCSI_OFF + cmd_len + in_size ||
sg_hd->result ) {
/* some error happened */
fprintf( stderr, "write(generic) result = 0x%x cmd = 0x%x\n",
sg_hd->result, i_buff[SCSI_OFF] );
perror("");
return status;
}
if (!o_buff) o_buff = i_buff; /* buffer pointer check */
/* retrieve result */
status = read( fd, o_buff, SCSI_OFF + out_size);
if ( status < 0 || status != SCSI_OFF + out_size || sg_hd->result ) {
/* some error happened */
fprintf( stderr, "read(generic) result = 0x%x cmd = 0x%x\n",
sg_hd->result, o_buff[SCSI_OFF] );
fprintf( stderr, "read(generic) sense "
"%x %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x\n",
sg_hd->sense_buffer[0], sg_hd->sense_buffer[1],
sg_hd->sense_buffer[2], sg_hd->sense_buffer[3],
sg_hd->sense_buffer[4], sg_hd->sense_buffer[5],
sg_hd->sense_buffer[6], sg_hd->sense_buffer[7],
sg_hd->sense_buffer[8], sg_hd->sense_buffer[9],
sg_hd->sense_buffer[10], sg_hd->sense_buffer[11],
sg_hd->sense_buffer[12], sg_hd->sense_buffer[13],
sg_hd->sense_buffer[14], sg_hd->sense_buffer[15]);
if (status < 0)
perror("");
}
/* Look if we got what we expected to get */
if (status == SCSI_OFF + out_size) status = 0; /* got them all */
return status; /* 0 means no error */
}
#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) );
/*
* +------------------+
* | struct sg_header | <- cmd
* +------------------+
* | copy of cmdblk | <- cmd + SCSI_OFF
* +------------------+
*/
if (handle_scsi_cmd(sizeof(cmdblk), 0, cmd,
sizeof(Inqbuffer) - SCSI_OFF, Inqbuffer )) {
fprintf( stderr, "Inquiry failed\n" );
exit(2);
}
return (Inqbuffer + SCSI_OFF);
}
#define TESTUNITREADY_CMD 0
#define TESTUNITREADY_CMDLEN 6
#define ADD_SENSECODE 12
#define ADD_SC_QUALIFIER 13
#define NO_MEDIA_SC 0x3a
#define NO_MEDIA_SCQ 0x00
int TestForMedium ( void )
{
/* request READY status */
static unsigned char cmdblk [TESTUNITREADY_CMDLEN] = {
TESTUNITREADY_CMD, /* command */
0, /* lun/reserved */
0, /* reserved */
0, /* reserved */
0, /* reserved */
0};/* reserved */
memcpy( cmd + SCSI_OFF, cmdblk, sizeof(cmdblk) );
/*
* +------------------+
* | struct sg_header | <- cmd
* +------------------+
* | copy of cmdblk | <- cmd + SCSI_OFF
* +------------------+
*/
if (handle_scsi_cmd(sizeof(cmdblk), 0, cmd,
0, NULL)) {
fprintf (stderr, "Test unit ready failed\n");
exit(2);
}
return
*(((struct sg_header*)cmd)->sense_buffer +ADD_SENSECODE) !=
NO_MEDIA_SC ||
*(((struct sg_header*)cmd)->sense_buffer +ADD_SC_QUALIFIER) !=
NO_MEDIA_SCQ;
}
void main( void )
{
fd = open(DEVICE, O_RDWR);
if (fd < 0) {
fprintf( stderr, "Need read/write permissions for "DEVICE".\n" );
exit(1);
}
/* print some fields of the Inquiry result */
printf( "%s\n", Inquiry() + INQUIRY_VENDOR );
/* look if medium is loaded */
if (!TestForMedium()) {
printf("device is unloaded\n");
} else {
printf("device is loaded\n");
}
}
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Generated: 2007-01-26 17:57:47