[ofa-general] [PATCH RFC v3 1/2] RDMA/Core: MEM_MGT_EXTENSIONS support

[Steve Wise]

Roland Dreier wrote:
>  > 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.
>
> Yes, the point of this verb is that the low-level driver owns the page
> list from when the fast register work request is posted until it
> completes.  This should be explicitly documented somewhere.
>
>   

I've added it to the comments for ib_alloc_fast_reg_page_list() as per 
Ralph Campbell's suggestion.


> However the reason for having the low-level driver implement it is so
> that all strange device-specific issues can be taken care of in the
> driver.  For instance mlx4 is going to require that the page list be
> aligned to 64 bytes, and will DMA from the memory, so we need to use
> dma_alloc_consistent().  On the other hand cxgb3 is just going to copy
> in software, so kmalloc is sufficient.
>
>  - R.
>