SCSI读取(10)和写(10)与SCSI通用接口

Question

我试图向SSD发出scsi 读(10)和写(10)。我使用此示例代码作为参考/基本代码。

这是我的scsi读物：

#define READ_REPLY_LEN 32
#define READ_CMDLEN 10
void scsi_read()
{
  unsigned char Readbuffer[ SCSI_OFF + READ_REPLY_LEN ];
  unsigned char cmdblk [ READ_CMDLEN ] =
      {        0x28,  /* command */
                  0,  /* lun/reserved */
                  0,  /* lba */
                  0,  /* lba */
                  0,  /* lba */
                  0,  /* lba */
                  0,  /* reserved */
                  0,  /* transfer length */
     READ_REPLY_LEN,  /* transfer length */
                  0 };/* reserved/flag/link */
  memset(Readbuffer,0,sizeof(Readbuffer));
  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(Readbuffer) - SCSI_OFF, Readbuffer )) {
      fprintf( stderr, "read failed\n" );
      exit(2);
  }
  hex_dump(Readbuffer,sizeof(Readbuffer));
}

这是我的scsi写的：

void scsi_write ( void )
{
  unsigned char Writebuffer[SCSI_OFF];
  unsigned char cmdblk [] =
      {        0x2A,  /* 0: command */
                  0,  /* 1: lun/reserved */
                  0,  /* 2: LBA */
                  0,  /* 3: LBA */
                  0,  /* 4: LBA */
                  0,  /* 5: LBA */
                  0,  /* 6: reserved */
                  0,  /* 7: transfer length */
                  0,  /* 8: transfer length */
                  0 };/* 9: control */

  memset(Writebuffer,0,sizeof(Writebuffer));
  memcpy( cmd + SCSI_OFF, cmdblk, sizeof(cmdblk) );
  cmd[SCSI_OFF+sizeof(cmdblk)+0] = 'A';
  cmd[SCSI_OFF+sizeof(cmdblk)+1] = 'b';
  cmd[SCSI_OFF+sizeof(cmdblk)+2] = 'c';
  cmd[SCSI_OFF+sizeof(cmdblk)+3] = 'd';
  cmd[SCSI_OFF+sizeof(cmdblk)+4] = 'e';
  cmd[SCSI_OFF+sizeof(cmdblk)+5] = 'f';
  cmd[SCSI_OFF+sizeof(cmdblk)+6] = 'g';
  cmd[SCSI_OFF+sizeof(cmdblk)+7] = 0;
  /*
   * +------------------+
   * | struct sg_header | <- cmd
   * +------------------+
   * | copy of cmdblk   | <- cmd + SCSI_OFF
   * +------------------+
   * | data to write    | 
   * +------------------+
   */

  if (handle_scsi_cmd(sizeof(cmdblk), 8, cmd, 
                      sizeof(Writebuffer) - SCSI_OFF, Writebuffer )) {
      fprintf( stderr, "write failed\n" );
      exit(2);
  }
}

在下面的示例中，我会这样做

1. scsi读
2. scsi写
3. scsi读

然后打印所写入的数据的六边形(scsi写)和读取的内容(scsi读取)。

Read(10)
[0000]   00 00 00 44 00 00 00 44   00 00 00 00 00 00 00 00   ...D...D ........
[0010]   00 2C 00 00 00 00 00 00   00 00 00 00 00 00 00 00   ........ ........
[0020]   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00   ........ ........
[0030]   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00   ........ ........
[0040]   00 00 00 00                                         ....

Write(10):
[0000]   00 00 00 00 00 00 00 24   00 00 00 00 00 00 00 00   ........ ........
[0010]   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00   ........ ........
[0020]   00 00 00 00 2A 00 00 00   00 00 00 00 00 00 41 62   ........ ......Ab
[0030]   63 64 65 66 67 00                                   cdefg.

Read(10):
[0000]   00 00 00 44 00 00 00 44   00 00 00 00 00 00 00 00   ...D...D ........
[0010]   04 00 20 00 70 00 02 00   00 00 00 0A 00 00 00 00   ....p... ........
[0020]   04 00 00 00 41 62 63 64   65 66 67 00 00 00 00 00   ....Abcd efg.....
[0030]   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00   ........ ........
[0040]   00 00 00 00                                         ....

再次运行这三个命令时，我应该用第一次读取Abcdefg。对吗？但是再运行一次也没什么改变。现在您可以假设，我使用的内存仍然拥有来自以前功能的数据，但是即使在memset(Readbuff,0,sizeof(Readbuff))发生之前运行了sys_read()，结果也是一样的。

我假设，我试图写的LBA可能是禁止写的，所以我读了缓存。但是在LBA上插入0x000-0xFF并不改变什么--这意味着我读取了相同的数据(Abcdefg)。

您知道用scsi通用接口进行读写的示例实现吗？

Answer 1

在SCSI中，LBA的单位和传输长度是块的，有时称为扇区。这几乎总是512字节。所以，你不能只读写32个字节。至少，您必须完成512个字节的==一个块。这一点是你需要解决的大部分问题。

在scsi_write实现中，传输长度为零，因此它实际上不会写入任何数据。

您应该对CDB和写/读数据使用不同的缓冲区。我怀疑对这些缓冲区的混淆导致您的实现在静态分配数组的末尾和ReadBuffer上编写。在缬磨下运行它，看看会出现什么。

最后，handle_scsi_cmd中的任何内容都可能出错。设置数据传输可能很棘手.特别是，确保在I/O标头的dxfer_direction: SG_DXFER_TO_DEV用于写入，SG_DXFER_FROM_DEV用于读取时，数据是直接向哪个方向进行的。

请查看如何进行读取(16)的示例。这更符合你想要实现的目标。

simple16.c