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

[Mark Lord <liml@rtr.ca>]

Albert Lee wrote:
> Tejun Heo 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.
>>
>> This patch adds ATA_DFLAG_DMADIR and make ata_dev_configure() set it
>> if atapi_dmadir is set or identify data indicates DMADIR is necessary.
>> atapi_xlat() is converted to check ATA_DFLAG_DMADIR before setting
>> DMADIR.
>>
>> Original patch is from Mark Lord.
>>
>> Signed-off-by: Tejun Heo <htejun@gmail.com>
>> Cc: Mark Lord <mlord@pobox.com>
>> ---
>> I don't have a bridge which sets DMADIR but so only checked atapi_dmadir
>> parameter.  Thanks.
>>
> 
> The patch looks good. However, it seems there is no realworld IDE-to-SATA
> bridge that requires DMADIR and also mangles IDENTIFY PACKET bit-15 of
> word-62 to indicate its presence.
> 
>>From the previous test of the IDE-to-SATA bridges, only the Sil 3611
> requires the host software to hint on ATAPI DMADIR. But Sil 3611 doesn't
> mangle IDENTIFY PACKET word-62:
> http://www.spinics.net/lists/linux-ide/msg01514.html
..

Ahh, great!  We have "history" here!

But there are more SATA bridges out there than the ones Alber has there
(SiI 3611/3811, Marvell 88i8030/88SA8040, Acard ARC770, JMicron JM20330).

There's the Marvell 88SA8050, and I have a funky looking thing here
that says "SataLink SPiF223A" on it (????).  I wonder what it does?
And how many other ones are there?

The Word62 patch (from Tejun) is simple enough that the "complexity"
point from before really doesn't hold water.

To be ATA compliant, we really should add it in.
But yes, it would also be good to see it in action.

That's more likely to happen in the general user community,
than in our limited circle of kernel folk with limited hardware.

Cheers