Question

我尝试向SSD发出scsi read(10)和write(10)。我使用this example code作为参考/基本代码。

这是我的scsi阅读：

#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写道：

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);
  }
}

在以下示例中，我执行

scsi read
scsi写
scsi read

我打印写入的数据的十六进制（scsi写入）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，我应该在第一次阅读时阅读Abcdefg。对？但是再次运行它们不会改变任您现在可以假设，我使用的内存仍然是以前功能的数据，但即使我在memset(Readbuff,0,sizeof(Readbuff))发生之前运行sys_read()，我也会得到相同的结果。

我认为，我试图写的LBA可能被禁止写，我读了缓存。但是，从0x00-0xFF对LBA地址进行交互不会改变任何内容 - 这意味着，我读取了相同的数据（Abcdefg）。

您是否知道使用scsi泛型接口进行scsi读取或写入的示例实现？

Answer 1

在SCSI中，LBA的单位和传输长度是块，有时称为扇区。这几乎总是512字节。因此，您不能只读取或写入32个字节。至少，你必须做512字节==一个块。这一点是您需要修复的大部分内容。

您的scsi_write实现中的传输长度为零，因此它实际上不会写入任何数据。

您应该为CDB和写入/读取数据使用不同的缓冲区。我怀疑关于这些缓冲区的混淆导致你的实现写入你的一个静态分配的数组和你的ReadBuffer的末尾。在valgrind下运行它，看看会出现什么。

最后，在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，确保您直接在I / O头的dxfer_direction中以哪种方式传输数据：SG_DXFER_TO_DEV用于写入，SG_DXFER_FROM_DEV用于读取。

查看这个如何进行读取的示例（16）。这更像是你想要完成的事情。

https://github.com/hreinecke/sg3_utils/blob/master/examples/sg_simple16.c

SCSI读取（10）和写入（10）与SCSI通用接口

1 个答案: