Re: [PATCH/RFC] libata: turn on the ATAPI DMADIR support per word 62 (revised)

[Jeff Garzik <jeff@garzik.org>]

Albert Lee wrote:
> Summary:
>   SiI 3611 is currently the only known chip that needs DMADIR.
> Since SiI 3611 doesn't implement the ATA-7 word 62 or mangle identify
> packet device data, it's hard to check the chip and turn on the DMADIR
> support automatically. (Currently the libata DMADIR support can be 
> turned on manually by module parameter.)

Wonderful test report, thanks a _bunch_ for investigating this.


> To turn on the DMADIR support automatically, maybe we can check whether
> the ATAPI device is bridged (by ata_dev_knobble()). If bridged, we can
> try to issue a ATAPI DMA read command to check if ATAPI DMA works.
> If not work, then try turning on DMADIR or turn off ATAPI DMA.

Sounds like more complexity than its worth, for one non-spec-compliant 
bridge chip.  The module option gets the 3611 going, so IMO the current 
level of support is adequate.

BTW, I found a 3611 here, and put it into my primary fileserver, 
attaching to a DMA-capable PATA CD-RW drive.

	Jeff