From: Andrey Savochkin <saw@saw.sw.com.sg> 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.
