On 7/9/25 13:40, Dragos Tatulea wrote:

For zerocopy (io_uring, devmem), there is an assumption that the
parent device can do DMA. However that is not always the case:
ScalableFunction devices have the DMA device in the grandparent.

This patch adds a helper for getting the DMA device for a netdev from
its parent or grandparent if necessary. The NULL case is handled in the
callers.

devmem and io_uring are updated accordingly to use this helper instead
of directly using the parent.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Fixes: 170aafe35cb9 ("netdev: support binding dma-buf to netdevice")
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
---
Changes in v1:
- Upgraded from RFC status.
- Dropped driver specific bits for generic solution.
- Implemented single patch as a fix as requested in RFC.
- Handling of multi-PF netdevs will be handled in a subsequent patch
   series.

RFC: https://lore.kernel.org/all/20250702172433.1738947-2-dtatulea@nvidia.com/ (local)

I can't say anything about the walking to grand parent part, but
the rest looks good.

Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

-- 
Pavel Begunkov