From: Andrey Savochkin <saw@xxxxxxxxxxxxx>
Date: Thu, 13 Jun 2002 12:57:53 +0400
On Wed, Jun 12, 2002 at 04:05:32PM -0700, David S. Miller wrote:
> No, it's worse than that.
>
> See how non-consistent memory is used by the eepro100 driver
> for descriptor bits? The skb->tail bits?
>
> That is very problematic.
What's the problem?
If it isn't allowed to do, then what is the meaning of PCI_DMA_BIDIRECTIONAL
mappings?
It's slow. Not wrong, just inefficient.
Descriptors were meant to be done using consistent mappings, not
"pci_map_*()"'d memory. The latter is meant to be used for long
linear DMA transfers to/from the device. It is not meant for things
the cpu pokes small bits of data in and out of, that is what
consistent DMA memory is for.
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