Messages in this thread | | | Date | Thu, 13 Dec 2001 17:17:22 +0100 (CET) | From | Gérard Roudier <> | Subject | Re: highmem, aic7xxx, and vfat: too few segs for dma mapping |
| |
On Wed, 12 Dec 2001, David S. Miller wrote:
> From: Gérard Roudier <groudier@free.fr> > 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, Gérard.
PS: Don't take the wrong way my statements against Sun stuff. In fact, I dislike almost everything that comes and came from them. :)
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |