From: David Mosberger <davidm@napali.hpl.hp.com>
Date: Sat, 7 Jun 2003 00:05:06 -0700
But you're creating a new mapping for the old buffer. What if you had
a DMA API implementation which consolidates multiple mapping attempts
of the same buffer into a single mapping entry (along with a reference
count)? That would break the workaround.
I hope nobody is doing this, it would probably break other things
we haven't considered yet.
You can't support all the BIO_MERGE_BOUNDARY stuff properly in
such a scheme. And you _WANT_ to support that when you have an
IOMMU, it shrinks the DMA descriptor addr/len entries a chip
has to DMA for each block I/O considerably.
Isn't the proper fix to (a) get a new buffer, (b) create a mapping for
the new buffer, (c) destroy the mapping for the old buffer. That
should guarantee a different bus address, no matter what the
DMA-mapping implementation.
I suppose this would work, fell free to code this up for the
tg3 driver for me because I certainly lack the time to do this.
-
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/
This archive was generated by hypermail 2b29 : Sat Jun 07 2003 - 22:00:32 EST