Re: [PATCH net-next v4 4/6] net: bcmgenet: add XDP_TX support

[Nicolai Buchwitz]

On 25.3.2026 05:03, Jakub Kicinski wrote:
> On Mon, 23 Mar 2026 13:05:33 +0100 Nicolai Buchwitz wrote:
> > Implement XDP_TX using ring 16 (DESC_INDEX), the hardware default
> > descriptor ring, dedicated to XDP TX for isolation from SKB TX queues.
> >
> > Ring 16 gets 32 BDs carved from ring 0's allocation. TX completion is
> > piggybacked on RX NAPI poll since ring 16's INTRL2_1 bit collides with
> > RX ring 0, similar to how bnxt, ice, and other XDP drivers handle TX
> > completion within the RX poll path.
> >
> > The GENET MAC has TBUF_64B_EN set globally, requiring every TX buffer
> > to start with a 64-byte struct status_64 (TSB). For local XDP_TX, the
> > TSB is prepended by backing xdp->data into the RSB area (unused after
> > BPF execution) and zeroing it. For foreign frames redirected from 
> > other
> > devices, the TSB is written into the xdp_frame headroom.
> >
> > The page_pool DMA direction is changed from DMA_FROM_DEVICE to
> > DMA_BIDIRECTIONAL to allow TX reuse of the existing DMA mapping.
>
> drivers/net/ethernet/broadcom/genet/bcmgenet.c:2420:27: warning: 
> variable 'tx_ring' set but not used [-Wunused-but-set-variable]
>  2420 |         struct bcmgenet_tx_ring *tx_ring;
>       |                                  ^

Missed during the refactoring (should be part of patch 5). I will 
address this in the next version of this series.

Thanks
Nicolai