Re: [Qemu-devel] [PATCH v2] add suport for ATA_PASSTHROUGH_xx scsi command

[Cong Meng <mc@linux.vnet.ibm.com>]

On Wed 01 Aug 2012 05:42:08 PM CST, Paolo Bonzini wrote:
> Il 01/08/2012 11:05, Cong Meng ha scritto:
>> +    case ATA_PASSTHROUGH_12:
>> +        if (dev->type != TYPE_ROM) {
>> +            if ((buf[2] & 0x3) == 2) {
>> +                cmd->xfer = buf[4] * dev->blocksize;
>> +            }
>> +        }
>> +        break;
>> +    case ATA_PASSTHROUGH_16:
>> +        if ((buf[2] & 0x3) == 2) {
>> +            cmd->xfer = ((buf[5] << 8) | buf[6]) * dev->blocksize;
>> +        }
>> +        break;
>
> Hmm, I think you're only handling this partially.

Ah, I will complete it.
Cong.

>
> Four bits of buf[2] count; bits 0..1 are T_LENGTH, bit 2 is BYTE_BLOCK,
> bit 4 is T_TYPE:
>
> If buf[2] is xxxxxx00, cmd->xfer = 0
>
> else
>
>     if buf[2] is xxxxx0xx, xfer_unit = 1
>     else if buf[2] is xxx0x1xx, xfer_unit = 512
>     else xfer_unit = dev->blocksize (this is when buf[2] is xxx1x1xx)
>
>     if buf[2] is xxxxxx01, set cmd->xfer to the FEATURES field
>     if buf[2] is xxxxxx10, set cmd->xfer to the SECTOR_COUNT
>
>     for ATA_PASSTHROUGH_16, if buf[1] bit 0 is 0, then cmd->xfer &= 255;
>
>     cmd->xfer *= xfer_unit;
>
> Also we cannot support buf[2] is xxxxxx11.  Please add a check to
> hw/scsi-generic.c, so that the request is failed in this case.
>
> This is better encapsulated in a separate function, of course.
>
> On top of this, the direction is not necessarily TO_DEV (as in the
> current code for scsi_cmd_xfer_mode).  It is TO_DEV if buf[2] bit 3
> (T_DIR) is zero; it is FROM_DEV if buf[2] bit 3 is one.
>
> Do you have a copy of the SAT (SCSI/ATA translation) standard?  This is
> all in paragraph 12.2.2.2 in my copy.
>
> Paolo
>