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Date: Thu, 10 Jul 2025 16:49:03 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Dragos Tatulea <dtatulea@nvidia.com>
Cc: <almasrymina@google.com>, <asml.silence@gmail.com>, Andrew Lunn
 <andrew+netdev@lunn.ch>, "David S. Miller" <davem@davemloft.net>, "Eric
 Dumazet" <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Simon
 Horman <horms@kernel.org>, Jens Axboe <axboe@kernel.dk>, Simona Vetter
 <simona.vetter@ffwll.ch>, Willem de Bruijn <willemb@google.com>, Kaiyuan
 Zhang <kaiyuanz@google.com>, <cratiu@nvidia.com>, <parav@nvidia.com>, Tariq
 Toukan <tariqt@nvidia.com>, <netdev@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, <io-uring@vger.kernel.org>
Subject: Re: [PATCH net] net: Allow non parent devices to be used for ZC DMA
Message-ID: <20250710164903.03a962fc@kernel.org>
In-Reply-To: <20250709124059.516095-2-dtatulea@nvidia.com>
References: <20250709124059.516095-2-dtatulea@nvidia.com>
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On Wed, 9 Jul 2025 15:40:57 +0300 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.

Sorry for the silence. I'll reply to Parav on the RFC, I don't think
the question I was asking was answered there.