sending various scsi commands through a single function - c

Question

I have been playing around with scsi command and I can send some basic commands like different inquirys and such.
I have been using this example to to generate my inquiry. I am working on making this example work with different scsi commands.
http://www.tldp.org/HOWTO/SCSI-Generic-HOWTO/pexample.html
I have changed to function to accept different scsi commands through a struct and it also returns a struct based on the output. This works with an inquiry flawlessly. However if I send a READ CAPACITY(16) command the function triggers on the if statement:
(io_hdr.info & SG_INFO_OK_MASK) != SG_INFO_OK)
I am new to scsi programming so I might be doing something totally wrong...
my READ CAPACITY(16) command is just this:
scsi_read_capacity.cmdblk[0]=0x9e;
scsi_read_capacity.cmdblk[13]=32;
the rest of the CDB are 0!
here is the code:
#include <stdio.h>
#include <sys/ioctl.h>
#include <scsi/sg.h>
/* global struct to store return data from a scsi cmd*/
typedef struct SCSI_data {
unsigned char data[1024];
unsigned char raw_sens[252];
unsigned char sense_key;
unsigned char additional_sense_code;
unsigned char additional_sense_qualifier;
unsigned char additional_sense_length;
unsigned char sense_data_descriptors[10][244];
int result;
} SCSI_data;
/* global struct to store return data from a scsi cmd*/
typedef struct SCSI_cmd {
int sg_fd;
unsigned char cmdblk[32];
int cmdblklength;
int allocation_length;
int xfer;
int timeout;
} SCSI_cmd;
SCSI_data send_scsicmd(SCSI_cmd cmdobject) {
int k;;
unsigned char inqBuff[cmdobject.allocation_length];
unsigned char sense_buffer[252];
SCSI_data output_data;
sg_io_hdr_t io_hdr;
/* Prepare INQUIRY command */
memset(&io_hdr, 0, sizeof(sg_io_hdr_t));
io_hdr.interface_id = 'S';
io_hdr.cmd_len = cmdobject.cmdblklength;
io_hdr.mx_sb_len = sizeof(sense_buffer);
io_hdr.dxfer_direction = cmdobject.xfer;
io_hdr.dxfer_len = cmdobject.allocation_length;
io_hdr.dxferp = inqBuff;
io_hdr.cmdp = cmdobject.cmdblk;
io_hdr.sbp = sense_buffer;
io_hdr.timeout = cmdobject.timeout;
if (ioctl(cmdobject.sg_fd, SG_IO, &io_hdr) < 0) {
output_data.result=2;
return output_data;
}
/* now for the error processing */
if ((io_hdr.info & SG_INFO_OK_MASK) != SG_INFO_OK) {
output_data.result=1;
if (io_hdr.sb_len_wr > 0) {
printf("INQUIRY sense data: ");
for (k = 0; k < io_hdr.sb_len_wr; ++k) {
if ((k > 0) && (0 == (k % 10)))
printf("\n ");
printf("0x%02x ", sense_buffer[k]);
}
printf("\n");
}
if (io_hdr.masked_status)
printf("INQUIRY SCSI status=0x%x\n", io_hdr.status);
if (io_hdr.host_status)
printf("INQUIRY host_status=0x%x\n", io_hdr.host_status);
if (io_hdr.driver_status)
printf("INQUIRY driver_status=0x%x\n", io_hdr.driver_status);
}
else { /* assume INQUIRY response is present */
output_data.result=0;
for (k=0;k<cmdobject.allocation_length;k++) {
output_data.data[k]=inqBuff[k];
}
}
return output_data;
}
int main(int argc, char * argv[]) {
FILE *driveptr=fopen(argv[1], "r");
int i;
SCSI_data scsi_data_read_capacity;
SCSI_cmd scsi_read_capacity;
scsi_read_capacity.sg_fd=fileno(driveptr);
scsi_read_capacity.cmdblk[0]=0x9e;
scsi_read_capacity.cmdblk[13]=32;
scsi_read_capacity.cmdblklength=16;
scsi_read_capacity.xfer=SG_DXFER_FROM_DEV;
scsi_read_capacity.allocation_length=32;
scsi_read_capacity.timeout=1000;
scsi_data_read_capacity=send_scsicmd(scsi_read_capacity);
if (scsi_data_read_capacity.result==0) {
printf(" capacity in blocks: %02x%02x%02x%02x%02x%02x%02x%02x\n",
scsi_data_read_capacity.data[0],
scsi_data_read_capacity.data[1],
scsi_data_read_capacity.data[2],
scsi_data_read_capacity.data[3],
scsi_data_read_capacity.data[4],
scsi_data_read_capacity.data[5],
scsi_data_read_capacity.data[6],
scsi_data_read_capacity.data[7]);
printf(" blocksize: %02x%02x%02x%02x\n",
scsi_data_read_capacity.data[8],
scsi_data_read_capacity.data[9],
scsi_data_read_capacity.data[10],
scsi_data_read_capacity.data[11]);
}
fclose(driveptr);
return 0;
}

Answer 1

I had just a small problem. My CDB was wrong!
I had to use this:
scsi_read_capacity.cmdblk[0]=0x9E;
scsi_read_capacity.cmdblk[1]=0x10;
scsi_read_capacity.cmdblk[13]=32;
the second byte had to be equal to 0x10, this is because the scsi cmd 0x9E is a service action command which accepts an argument in the second byte which defines its behavior!