使用SCSI Generic Driver與usb讀卡機進行讀寫

利用SCSI Generic Driver 與usb讀卡機溝通

1. 在linuxconfig中勾選 SCSI support--> SCSI generic support

2. 在程式中需要include

3. sg_io_hdr struct介紹

typedef struct sg_io_hdr
{
int interface_id; /* [i] 'S' for SCSI generic (required) */
int dxfer_direction; /* [i] 資料傳輸方向 (SG_DXFER_FROM_DEV, SG_DXFER_TO_DEV, SG_DXFER_NONE) */
unsigned char cmd_len; /* [i] SCSI 指令長度 ( <= 16 bytes) */
unsigned char mx_sb_len; /* [i] max length to write to sbp */
unsigned short iovec_count; /* [i] 0 implies no scatter gather */
unsigned int dxfer_len; /* [i] 讀取寫入資料長度 */
void * dxferp; /* [i], [*io] points to data transfer memory
or scatter gather list */
unsigned char * cmdp; /* [i], [*i] points to command to perform */
unsigned char * sbp; /* [i], [*o] points to sense_buffer memory */
unsigned int timeout; /* [i] MAX_UINT->no timeout (unit: millisec) */
unsigned int flags; /* [i] 0 -> default, see SG_FLAG... */
int pack_id; /* [i->o] unused internally (normally) */
void * usr_ptr; /* [i->o] unused internally */
unsigned char status; /* [o] scsi status */
unsigned char masked_status;/* [o] shifted, masked scsi status */
unsigned char msg_status; /* [o] messaging level data (optional) */
unsigned char sb_len_wr; /* [o] byte count actually written to sbp */
unsigned short host_status; /* [o] errors from host adapter */
unsigned short driver_status;/* [o] errors from software driver */
int resid; /* [o] dxfer_len - actual_transferred */
unsigned int duration; /* [o] time taken by cmd (unit: millisec) */
unsigned int info; /* [o] auxiliary information */
} sg_io_hdr_t; /* 64 bytes long (on i386) */

PS. http://tldp.org/HOWTO/SCSI-Generic-HOWTO/index.html 有詳細介紹

4. 需要注意裝置被掛載的位置。我的usb讀卡機裝置利用generic driver的話，是被掛載於/dev/scsi/host0/bus0/target0/lun0/generic。
一般則是會在 /dev/sg0 or /dev/sg1。

5. 範例程式 ：實做了 inquiry (0x12) and read10 (0x28) command.


#include
#include
#include
#include
#include
#include
#include /* take care: fetches glibc's /usr/include/scsi/sg.h */

/* This is a simple program executing a SCSI INQUIRY command using the
sg_io_hdr interface of the SCSI generic (sg) driver.

* Copyright (C) 2001 D. Gilbert
* This program is free software. Version 1.01 (20020226)
*/

#define INQ_REPLY_LEN 96
#define INQ_CMD_CODE 0x12
#define INQ_CMD_LEN 6

#define RD_CMD_LEN 10
#define RD_CMD_CODE 0x28
#define RD_LEN 512

int main(int argc, char * argv[])
{
int sg_fd, k;
int readcmd = 0;
int rlen = 512;
unsigned char inqCmdBlk[INQ_CMD_LEN] =
{INQ_CMD_CODE, 0, 0, 0, INQ_REPLY_LEN, 0};
unsigned char rdCmdBlk[RD_CMD_LEN];


/* This is a "standard" SCSI INQUIRY command. It is standard because the
* CMDDT and EVPD bits (in the second byte) are zero. All SCSI targets
* should respond promptly to a standard INQUIRY */
unsigned char inqBuff[INQ_REPLY_LEN];
unsigned char sense_buffer[32];

unsigned char rdBuff[RD_LEN];

sg_io_hdr_t io_hdr;

if (2 > argc) {
printf("Usage: 'sg_simple0 '\n");
return 1;
}

if (argc == 3) {
if (strcmp(argv[2],"r")==0) readcmd = 1;
}

if ((sg_fd = open(argv[1], O_RDONLY)) < 0) {
/* Note that most SCSI commands require the O_RDWR flag to be set */
perror("error opening given file name");
return 1;
}
/* It is prudent to check we have a sg device by trying an ioctl */
if ((ioctl(sg_fd, SG_GET_VERSION_NUM, &k) < 0) || (k < 30000)) {
printf("%s is not an sg device, or old sg driver\n", argv[1]);
return 1;
}

if (readcmd) {
memset(rdCmdBlk,0,sizeof(rdCmdBlk));
rdCmdBlk[0] = RD_CMD_CODE;
rdCmdBlk[8] = 1;

memset(&io_hdr, 0, sizeof(sg_io_hdr_t));
io_hdr.interface_id = 'S';
io_hdr.cmd_len = sizeof(rdCmdBlk);
/* io_hdr.iovec_count = 0; */ /* memset takes care of this */
io_hdr.mx_sb_len = sizeof(sense_buffer);
io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
io_hdr.dxfer_len = RD_LEN;
io_hdr.dxferp = rdBuff;
io_hdr.cmdp = rdCmdBlk;
io_hdr.sbp = sense_buffer;
io_hdr.timeout = 20000; /* 20000 millisecs == 20 seconds */
/* io_hdr.flags = 0; */ /* take defaults: indirect IO, etc */
/* io_hdr.pack_id = 0; */
/* io_hdr.usr_ptr = NULL; */
} else {
/* Prepare INQUIRY command */
memset(&io_hdr, 0, sizeof(sg_io_hdr_t));
io_hdr.interface_id = 'S';
io_hdr.cmd_len = sizeof(inqCmdBlk);
/* io_hdr.iovec_count = 0; */ /* memset takes care of this */
io_hdr.mx_sb_len = sizeof(sense_buffer);
io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
io_hdr.dxfer_len = INQ_REPLY_LEN;
io_hdr.dxferp = inqBuff;
io_hdr.cmdp = inqCmdBlk;
io_hdr.sbp = sense_buffer;
io_hdr.timeout = 20000; /* 20000 millisecs == 20 seconds */
/* io_hdr.flags = 0; */ /* take defaults: indirect IO, etc */
/* io_hdr.pack_id = 0; */
/* io_hdr.usr_ptr = NULL; */
}

if (ioctl(sg_fd, SG_IO, &io_hdr) < 0) {
perror("sg_simple0: Inquiry SG_IO ioctl error");
return 1;
}

/* now for the error processing */
if ((io_hdr.info & SG_INFO_OK_MASK) != SG_INFO_OK) {
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 */
if (readcmd) {
char *p = (char *)rdBuff;
printf("read buffer content:\n");
printf("byte 511: %x, byte 512: %x\n",*(p+510),*(p+511));
}else {
char * p = (char *)inqBuff;
printf("Some of the INQUIRY command's response:\n");
printf(" %.8s %.16s %.4s\n", p + 8, p + 16, p + 32);
printf("INQUIRY duration=%u millisecs, resid=%d\n",
io_hdr.duration, io_hdr.resid);
}
}
close(sg_fd);
return 0;
}