ioctrl using SCSI pass through - c++

Question

Using Windows I can easily communicate with my USB device using the following simplified code:
DWORD dwJunk; // discard results from DeviceIOControl()
int iReply;
char cBuffer[100];
// cBuffer is initialized here.
HANDLE hDevice; // handle to the drive to be examined
CString sDrive = _T(\\\\.\\H:); // drive H: for this test
hDevice = CreateFile(sDrive, // drive to open
GENERIC_READ | GENERIC_WRITE, // read and write access to the drive
FILE_SHARE_READ | FILE_SHARE_WRITE, // share mode
NULL, // default security attributes
OPEN_EXISTING, // disposition
0, // file attributes
NULL); // do not copy file attributes
iReply = DeviceIoControl(hDevice, IOCTL_SCSI_PASS_THROUGH_DIRECT, &cBuffer, sizeof(cBuffer), &cBuffer, sizeof(cBuffer), &dwJunk, (LPOVERLAPPED)NULL);
I'm trying to do the same in linux but have not been able to figure out the ioctrl() parameters, or better put the structure. A code snippet would be vey much appreciated. Thanks.

Answer 1

Unfortunately the code I modified using your link didn't return any results. Here's the stripped code I used. ioctl() returned without errors:
#define DEF_TIMEOUT 5000 // 5 seconds
char cDiskName[] = "/dev/sg3";
int fd = open(cDiskName, O_RDWR);
if (fd < 0)
{
printf("Open error: %s, errno=%d (%s)\n", cDiskName, errno, strerror(errno));
return 1;
}
unsigned char turCmbBlk[] = {0x00, 0, 0, 0, 0, 0};
struct sg_io_hdr io_hdr;
unsigned char cIOBuffer[100];
// buffer initialization code omitted
memset(&io_hdr, 0, sizeof(struct sg_io_hdr));
io_hdr.interface_id = 'S';
io_hdr.cmd_len = sizeof(turCmbBlk);
io_hdr.mx_sb_len = sizeof(cIOBuffer);
io_hdr.dxfer_direction = SG_DXFER_NONE;
io_hdr.cmdp = turCmbBlk;
io_hdr.sbp = cIOBuffer;
io_hdr.timeout = DEF_TIMEOUT;
if (ioctl(fd, SG_IO, &io_hdr) < 0)
{
printf("ioctl error: errno=%d (%s)\n", errno, strerror(errno));
}
// Code returned here without any errors but cIOBuffer remains unchanged.
Maybe the call needs a different request code?

Answer 2

Here's some more documentation:
Notes on Linux's SG driver version 2.1.36
SCSI-Programming, page 8 (handle_SCSI_cmd function), page 9, page 11 (example) and some more
Generic SCSI Target Subsystem for Linux

Answer 3

See here:
#include <sys/ioctl.h>
int ioctl(int d, int request, ...);
Parameters:
Filedescriptor (must be open!)
Request code number (depends on device)
Untyped pointer to memory (going to / coming from driver)
Example
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/usbdevice_fs.h>
void main(int argc, char **argv)
{
const char *filename;
int fd;
filename = argv[1];
fd = open(filename, O_WRONLY);
ioctl(fd, USBDEVFS_RESET, 0);
close(fd);
return;
}
Documentation:
ioctl(2) - Linux man page
IOCTL(2)
Generic I/O Control operations (GNU libc)
The ioctl() Requests
usb.c (Example that might help you)
Linux / Unix Command: ioctl
How to Reset USB Device in Linux (Example)
An example Program with IOCTL
Edit
#define BUFF_SIZE 100 // - Buffersize
#define DEF_TIMEOUT 5000 // 5 seconds
char cDiskName[] = "/dev/sg3";
int fd = open(cDiskName, O_RDWR);
if (fd < 0)
{
printf("Open error: %s, errno=%d (%s)\n", cDiskName, errno, strerror(errno));
return 1;
}
unsigned char turCmbBlk[] = {0x00, 0, 0, 0, 0, 0};
struct sg_io_hdr *p = (struct sg_io_hdr *) malloc(sizeof(struct sg_io_hdr)); // - dynamic memory allocation - free() required somewhere
unsigned char cIOBuffer[BUFF_SIZE];
unsigned char replyBuffer[BUFF_SIZE]; // - dxfer buffer
// buffer initialization code omitted
memset(p, 0, sizeof(struct sg_io_hdr));
p->interface_id = 'S';
p->cmd_len = sizeof(turCmbBlk);
p->mx_sb_len = BUFF_SIZE;
p->dxfer_direction = SG_DXFER_NONE;
p->cmdp = turCmbBlk;
p->sbp = cIOBuffer;
p->timeout = DEF_TIMEOUT;
p->flags = SG_FLAG_DIRECT_IO; // - Does this help?
p->dxferp = replyBuffer; // - Set dxferp buffer - (A)
p->dxfer_len = BUFF_SIZE; // - buffersize
if (ioctl(fd, SG_IO, p) < 0)
{
printf("ioctl error: errno=%d (%s)\n", errno, strerror(errno));
}
// Code returned here without any errors but cIOBuffer remains unchanged.
Note (A): Please try setting your input / output buffer you work on here.
Documentation:
SCSI Generic HOWTO, SG_IO_HDR_T
Tour the Linux generic SCSI driver