FUJITA Tomonori wrote:
On Wed, 26 Sep 2007 06:11:45 -0400
Jeff Garzik <jeff@xxxxxxxxxx> wrote:
FUJITA Tomonori wrote:
This patch moves blk_queue_max_segment_size to scsi_alloc_queue from
llds. It enables scsi_add_host to tells iommu lld's
dma_max_segment_size. If a low-level driver doesn't specify
dma_max_segment_size, scsi-ml uses 65536 (MAX_SEGMENT_SIZE). So there
are not any functional changes.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
---
drivers/scsi/hosts.c | 5 +++++
drivers/scsi/scsi_lib.c | 1 +
include/scsi/scsi_host.h | 6 ++++++
3 files changed, 12 insertions(+), 0 deletions(-)
hmmmmm... All the patches look technically correct, but IMO this really
should behave more the the dma_mask interface: platform sets a sane
dma_mask (usually 0xffffffff), and LLDD calls dma_set_mask() or
pci_set_dma_mask().
Thus, IMO an LLDD should call dma_set_max_seg(), and then SCSI midlayer
can obtain that value from struct device.
Yeah, I agreed that max_segment_size should work like dma_mask (that's
why I simply put max_segment_size to device structure).
Yep!
scsi_debug doesn't use dma but calls blk_queue_max_segment_size (I
guess that it wants large I/Os). If we can remove it (thanks to
chaining sg), scsi-ml gets that value that llds set via
dma_set_max_seg and calls blk_queue_max_segment_size.
[/me checks the code] Actually scsi_debug has its own pseudo-bus and
struct device, so it sounds like scsi_debug can call dma_set_max_seg()
just like any other LLDD?
Maybe dev_set_max_seg() is a better name, if people get really picky (I
don't care).
Jeff
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