On Wed, 12 Dec 2001, David S. Miller wrote:
> From: Gérard Roudier <firstname.lastname@example.org>
> Date: Wed, 12 Dec 2001 21:24:59 +0100 (CET)
> A N% loss for the 99% case in order to support the 1% is close to N%
> loss. So, each time we bloat or complexify the code with no relevance for
> the average case, the overall difference cannot be a win.
> Do you know, you can use this N% loss to implement handling of the
> very problem you have wrt. sym53c8xx hw bugs? :-)
What hw bugs ? :-)
The driver is very fortunate. Based on DELs, only a few known hw bugs have
had to be worked-around by sym drivers. In fact, you can avoid most bugs,
by taking into account usual bugs in PCI hw. When I have made sym53c8xx
from ncr53c8xx, I had some clues in mind.
The 16MB/32MB boundary I pointed out can only affect sym53c896 rev. 1, and
only in not very likely situations. In plan to resurrect the work-around
in Linux sym_glue.c if pci_map_sg() will not want to handle the issue.
So, on paper, you were talking about a single unlikely to happen hw bug.
> To be honest all the machinery to handle the problems you have
> described are there today, even with IOMMU's present. The generic
> block layer today knows when IOMMU is being used, it knows what kind
> of coalescing can and will be done by the IOMMU support code (via
> DMA_CHUNK_SIZE), and therefore it is capable of adhering to any
> restrictions you care to describe to the block layer.
Will look into all these great things over the week-end and let you all
know my remarks if any.
> It's only a matter of coding on Jens's part :-)
Jen's seems to be a great and very courageous coder, so let me trust him
not to miss anything important. :)
Thanks for your reply,
PS: Don't take the wrong way my statements against Sun stuff. In fact, I
dislike almost everything that comes and came from them. :)
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