On Thu, 28 Jun 2001 Andries.Brouwer@cwi.nl wrote:
> From: Andre Hedrick <andre@aslab.com>
>
> You know yourself first and all the screwed up ATAPI products that are
> still using SFF-8020 that has been obsoleted before I start maintaining
> the subsystem three plus years ago.
>
> Hi Andre -
>
> Why precisely is complying to SFF-8020 broken?
> That was the standard. The standard that Microsoft required.
You have stated it clearly it is past tense.
> Other people made a different standard, and claimed that theirs
> was better or more official or whatever, but reality is that
> the products were not manufactured following this so-called
> better standard.
Ignoring "junk hardware" is not practical it will bite you everyday all
day long.........Best example is VIA.
> You are a good disciple of Hale, but it is no use ignoring the
If one is going to learn the rules it is best to have learned from on of
the "Fathers of ATA", and given that I have been crowned "Hale Jr." I take
this a compliment. The reality is that I am not anywhere in the same
class of understanding as Hale Landis, but getting there.
> fact that a very large number of devices was made following SFF-8020.
> These devices are not necessarily screwed, they tend to work fine,
> although both ATA and ATAPI devices have their quirks.
If they all did the same thing (regardless of class) it would be a
different issue. Basic things like asking for N amounts of data and
getting back N+M > N the buffer allocated. Or worse is the under
data-run. Other issues are DRQ, failure to hold/set busy-bit.
The ATAPI people do not even follow the rules in the defunct guide.
> SFF-8020, later INF-8020, became part of ATA/ATAPI-4 (1998).
> The T13 people that merged SFF-8020 and produced ATA/ATAPI-4
> changed a few details about how a master is supposed to react
> when a nonexistent slave is selected. Nobody really noticed,
That point is only important during POST and execution of drive
diagnostics command and Linux does not call that command.
> and ATA/ATAPI-5 still had the same requirements. But then long
> discussions about this difference caused ATA/ATAPI-6 to go back
> to the original SFF-8020 requirements. Do you disagree with this
> description of history? If you agree then it is not SFF-8020
> but ATA/ATAPI-4 and ATA/ATAPI-5 that today must be considered broken
> in this respect. I am referring to Section 9.16.1 of these standards.
>
> Maybe there are other things in SFF-8020 that you consider broken?
See above, regardless of the brokeness whe have to mucky with it.
So I move to develop to a standard that I have influence and direction
control, then deal with the exceptions.
ATA-X created the "packet-command" and "data-phase-handlers" based on the
zero-bit in the error_feature task-register.
Lastly it does not exist anymore, a real problem for manufacturers
building product on a document that does not exist. Worse is that there
are companies making hardware based on SFF-8020 v2.5!
Cheers,
Andre Hedrick
ASL Kernel Development
Linux ATA Development
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