firewire: Add a comment to describe why we split the sg list.
Signed-off-by: Kristian Hoegsberg <krh@redhat.com> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
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@ -926,7 +926,10 @@ static int sbp2_command_orb_map_scatterlist(struct sbp2_command_orb *orb)
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/*
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* Convert the scatterlist to an sbp2 page table. If any
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* scatterlist entries are too big for sbp2 we split the as we go.
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* scatterlist entries are too big for sbp2, we split them as we
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* go. Even if we ask the block I/O layer to not give us sg
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* elements larger than 65535 bytes, some IOMMUs may merge sg elements
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* during DMA mapping, and Linux currently doesn't prevent this.
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*/
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for (i = 0, j = 0; i < count; i++) {
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sg_len = sg_dma_len(sg + i);
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