Re: [PATCH net] net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG

[Simon Horman <horms@kernel.org>]

On Tue, Aug 11, 2026 at 10:38:55AM +0530, Siddharth Vadapalli wrote:
> On 10/08/26 22:26, Simon Horman wrote:
> > This is an AI-generated review of your patch. The human sending this
> > email has considered the AI review valid, or at least plausible.
> > Full review at: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260807111738.2055900-1-s-vadapalli@ti.com?part=1
> > ---
> > --- Patch [1]: [PATCH net] net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG ---
> > commit b0ed959d350c90d8b49f6f81eba7461fbc86dcf4
> > Author: Siddharth Vadapalli <s-vadapalli@ti.com>
> > 
> > net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG
> > 
> > The RX path extracts the ingress MAC port ID from the CPPI5 descriptor's
> > 16-bit Source Tag. Only the lower 8 bits carry the port ID, so the patch
> > masks the value with 0xFF before it is used as an index into
> > common->ports[].
> > 
> > > diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> > > index 434a31080855..6330540979d7 100644
> > > --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> > > +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> > > @@ -1310,6 +1310,8 @@ static int am65_cpsw_nuss_rx_packets(struct am65_cpsw_rx_flow *flow,
> > >   	k3_udma_glue_rx_cppi5_to_dma_addr(rx_chn->rx_chn, &buf_dma);
> > >   	pkt_len = cppi5_hdesc_get_pktlen(desc_rx);
> > >   	cppi5_desc_get_tags_ids(&desc_rx->hdr, &port_id, NULL);
> > > +	/* Port ID is contained in the lower 8-bits of the 16-bit Source Tag */
> > > +	port_id &= 0xFF;
> > >   	dev_dbg(dev, "%s rx port_id:%d\n", __func__, port_id);
> > >   	port = am65_common_get_port(common, port_id);
> > >   	ndev = port->ndev;
> > 
> > [Severity: High]
> > [Finding: main-1-0]
> > [Sources: opus-5]
> > 
> > The missing range check on port_id is pre-existing and not introduced by
> > this patch, but since the change is specifically about avoiding the
> > out-of-bounds access, would it be worth validating the value instead of
> > relying only on the mask?
> 
> Hardware guarantees a valid Port ID in the lower 8-bits. A Software check is
> an unnecessary overhead and will impact performance since this is on the
> data-path and is not a one-time check during initialization.

...

Hi Siddharth,

Thanks for addressing the AI generated review.
This all looks good to me now.

Reviewed-by: Simon Horman <horms@kernel.org>