Re: Q: how to send ATA cmds to USB drive?

Herbert Rosmanith
2006-06-12T10:08:20Z

> the userland program looks like this:
>
> memset(cmd,0,16);
> cmd[0]=0x24;
> cmd[1]=0x24;
> cmd[2]=0x01;
> cmd[3]=0x01;
...
> if ((i=ioctl(fd,SG_IO,&ioh))==-1)
> die("ioctl");
>
...
> the data really sent is "0x24 0x04 0x01 0x01", which means that 0x20 gets
> cleared in byte 2 (for whatever reason).
>
> do you have any idea why the data is modified and how I can prevent this?

ok, got it:

int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
...
/*
* If SCSI-2 or lower, store the LUN value in cmnd.
*/
if (cmd->device->scsi_level <= SCSI_2) {
cmd->cmnd[1] = (cmd->cmnd[1] & 0x1f) |
(cmd->device->lun << 5 & 0xe0);
}

hm. now what .... ? If scsi-2 requires this, and the device is scsi-2 (in fact,
cmd->device->scsi_level equals 3, which means SCSI_2) then the device is a violation
of the scsi-specs. do you have any suggestion how to fix this (beside from commenting
the source)

kind regards,
herbert rosmanith