Re: [PATCH][RT] 2.6.24-rc2-rt1 drivers/dma/ioat_dma.c compile fix

On Nov 16, 2007 3:57 AM, Sven-Thorsten Dietrich <sdietrich@xxxxxxxxxx>
wrote:
Compile fix for new code in -rc2.

I'm not positive about the insertion point...

Subject: compile error fix (needs review)

RT changes __list_splice to require prev and next pointers.

This changes the use in the new code to list_splice_tail,
but the optimal insertion point needs to be analyzed.

Signed-off-by: Sven-Thorsten Dietrich <sdietrich@xxxxxxx>

---
drivers/dma/ioat_dma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.23/drivers/dma/ioat_dma.c
===================================================================
--- linux-2.6.23.orig/drivers/dma/ioat_dma.c
+++ linux-2.6.23/drivers/dma/ioat_dma.c
@@ -244,7 +244,7 @@ static dma_cookie_t ioat_tx_submit(struc
/* write address into NextDescriptor field of last desc in
chain */
to_ioat_desc(ioat_chan->used_desc.prev)->hw->next =

first->async_tx.phys;
- __list_splice(&new_chain, ioat_chan->used_desc.prev);
+ list_splice_tail(&new_chain, ioat_chan->used_desc.prev);


NAK.

These functions do insertions differently. The 'prev' is pointing to
the last valid descriptor in the queue and you really want to get the
new_chain stuck on after this. Your list_splice_tail() will insert the
new_chain just before it which will muck up the order of the DMA
requests.

You might have more success with
list_splice_tail(&new_chain, ioat_chan->used_desc);
where used_desc points to the whole list, rather than using the .prev
pointer to a specific node.

Please copy me on future ioatdma related comments.

Thanks,
sln
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