On Wed, Mar 16 2005, Christoph Hellwig wrote:
On Wed, Mar 16, 2005 at 05:53:39PM +0100, Jens Axboe wrote:
The list doesn't really need dma mapping at that point, the problem here is that the driver needs to punt to pio mode because of foo. So calling pci/dma_map_* is pointless, since the CPU will have to do the transfer anyways. What the driver is really looking for at this point, is a way to map the pages in the sglist to a virtual address.
Given that there's quite a few cases of this "problem" it would be nice to have common helpers for it. Especially as it's really difficult when we allow merging of sg list entries
I thought about that when writing the above, but is there really more than one case for SCSI drivers? If there is, sure lets add the helpers. But I would consider it a quite rare occurence, I've never seen it before.
I got lost here. If you are talking about the need to kmap a sglist then software iscsi has it. iscsi-sfnet used to do
while (...)
kmap()but I fixed that (I think I need to use kmap_atomic though, is that correct or is it just a performance improvement - I am calling kmap from a thread too so). I just added kmap_atomic to open-iscsi and I believe pyx does something similar to the loop above.
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