linux-kernel - Re: [v4, net-next 2/7] bng

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Message-ID: <CANXQDtaLFQc3XRrLEH2AytcZvkeUdD9AW8=KUwqGQvM+=Q6M2w@mail.gmail.com>
Date: Fri, 16 Jan 2026 22:28:19 +0530
From: Bhargava Chenna Marreddy <bhargava.marreddy@...adcom.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	andrew+netdev@...n.ch, horms@...nel.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, michael.chan@...adcom.com, 
	pavan.chebbi@...adcom.com, vsrama-krishna.nemani@...adcom.com, 
	vikas.gupta@...adcom.com, 
	Rajashekar Hudumula <rajashekar.hudumula@...adcom.com>
Subject: Re: [v4, net-next 2/7] bng_en: Add RX support

On Tue, Jan 13, 2026 at 1:14 AM Bhargava Chenna Marreddy
<bhargava.marreddy@...adcom.com> wrote:
>
> On Thu, Jan 8, 2026 at 3:15 PM Paolo Abeni <pabeni@...hat.com> wrote:
> >
> > On 1/5/26 8:21 AM, Bhargava Marreddy wrote:
> > > +
> > > +     dma_sync_single_for_device(bd->dev, mapping, bn->rx_copybreak,
> > > +                                bn->rx_dir);
> >
> > Why is the above needed?
>
> Since the buffer is being reused, the for_device sync hands ownership
> back to the hardware.
> This ensures the memory is ready for the next DMA transfer and
> maintains consistency on non-coherent architectures.
> Any concerns with this?

Thanks, Paolo. You're correct. I took another look and realized the
for_device sync
is redundant here since the CPU only reads the data and hasn't written
to the buffer.
I'll remove this in the next revision.

Thanks,
Bhargava Marreddy

>
> >
> > > +
> > > +     skb_put(skb, len);
> > > +
> > > +     return skb;
> > > +}
> > > +

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