Re: Any objections/comments on axing out old ATA stack?

On Mar 28, 2013, at 8:00 AM, Ian Lepore <ian_at_FreeBSD.org> wrote:

> On Thu, 2013-03-28 at 09:17 +0200, Alexander Motin wrote:
>> On 28.03.2013 02:43, Adrian Chadd wrote:
>>> My main concern with the new stuff is that it requires CAM and that's
>>> reasonably big compared to the standalone ATA code.
>>> 
>>> It'd be nice if we could slim down the CAM stack a bit first; it makes
>>> embedding it on the smaller devices really freaking painful.
>> 
>> Are there many boards now with ATA, but without USB? But I agree, it 
>> should be checked.
>> 
> 
> It's not necessarily what the boards have but how they're used.  We use
> industrial SBCs at work that have ata compact flash sockets on the board
> which we do use, and usb interfaces which we don't use.
> 
> I've never tested the new ata+cam stuff on some of these boards, most
> based on Cyrix, Via, Geode, and VortexD86 chipsets.  The older ata code
> works, but not always very well -- for example, we usually have to set
> hw.ata.ata_dma=0 for absolutely no reason we've ever been able to figure
> out except that if we leave it enabled we get DMA errors and panics on
> some CF cards and not on others.  I have no idea whether to expect such
> things to be better, worse, or no different by changing to the ata+cam
> way of doing things (but I don't really have time to do extensive
> testing right now either).
> 


The legacy ATA code was hard to maintain, very buggy (as you point out), and
is essentially unmaintained.  Also, IIRC, the legacy stack simply cannot support
NCQ tagged queueing.

I think that Alexander has done a superb job with both developing and supporting
the CAM_ATA stack.

Scott