Or Gerlitz wrote:
Steve Wise wrote:
- device-specific alloc/free of physical buffer lists for use in fast
register work requests. This allows devices to allocate this memory as
needed (like via dma_alloc_coherent).
Steve,
Reading through the suggested API / patches and the previous threads I
was not sure to understand if the HW driver must not assume that it has
the ownership on the page --list-- structure until the registration work
request is completed - or not.
Yes, the driver owns the page list structure until the WR completes (ie
is reaped by the consumer via poll_cq()).
Now, if ownership can not be assumed (eg as for the SG list elements
pointed by send/recv WR), the driver has to clone it anyway, and thus I
don't see the need in the ib_alloc/free_fast_reg_page_list verbs.
If ownership can be assumed, I suggest to have the core use the
implementation of these two verbs as you did that for the Chelsio driver
in case the HW driver did not implement it (i.e instead of returning
ENOSYS). In that case, the alloc_list verb should do DMA mapping FROM
device (I think...) since the device is going to do DMA to read the page
list, and the free_list verb should do DMA unmapping, etc.
Some devices don't need DMA mappings at all (chelsio for instance). The
idea of a device-specific method was so the device could allocate a
bigger structure to hold its own context info. So a core service that
sets up DMA, in my opinion, isn't really useful.
Steve.
Or.
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