Re: [PATCH] libata-scsi: automatically use DMADIR if drive/bridge requires it

[Mark Lord <liml@rtr.ca>]

Jeff Garzik wrote:
> Mark Lord wrote:
>> Back in 2.6.17-rc2, a libata module parameter was added for atapi_dmadir.
>>
>> That's nice, but most SATA devices which need it will tell us about it
>> in their IDENTIFY PACKET response, as bit-15 of word-62 of the
>> returned data (as per ATA7, ATA8 specifications).
>>
>> So for those which specify it, we should automatically use the DMADIR 
>> bit.
>> Otherwise, disc writing will fail by default on many SATA-ATAPI drives.
>>
>> Signed-off-by: Mark Lord <mlord@pobox.com>
>>
>> --- old/drivers/ata/libata-scsi.c    2008-02-18 14:45:08.000000000 -0500
>> +++ linux/drivers/ata/libata-scsi.c    2008-02-18 14:53:02.000000000 
>> -0500
>> @@ -2543,9 +2543,10 @@
>>         qc->tf.protocol = ATAPI_PROT_DMA;
>>         qc->tf.feature |= ATAPI_PKT_DMA;
>>
>> -        if (atapi_dmadir && (scmd->sc_data_direction != DMA_TO_DEVICE))
>> -            /* some SATA bridges need us to indicate data xfer 
>> direction */
>> -            qc->tf.feature |= ATAPI_DMADIR;
>> +        /* some SATA bridges need us to indicate data xfer direction */
>> +        if (atapi_dmadir || (dev->id[62] & 0x8000))
>> +            if (scmd->sc_data_direction != DMA_TO_DEVICE)
>> +                qc->tf.feature |= ATAPI_DMADIR;
> 
> Regardless of the historical usage (or lack thereof) of that I.D. word, 
> I would prefer
> 
> 1) an ata version check
> 
> 2) a simple wrapper in linux/ata.h, similar to the many that already exist
> 
> So, conditional ACK...
..

Good.  As I said, I don't expect to be doing this,
so if anyone else wants to fix this issue in libata
they are more than welcome to take the above and build on it.

Cheers