linux-kernel - Re: [PATCH net-next v4 5/9] net: add devmem TCP TX documentation

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Message-ID: <Z7bkL7uuy8prxfTe@archie.me>
Date: Thu, 20 Feb 2025 15:13:35 +0700
From: Bagas Sanjaya <bagasdotme@...il.com>
To: Mina Almasry <almasrymina@...gle.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	virtualization@...ts.linux.dev, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Donald Hunter <donald.hunter@...il.com>,
	Jonathan Corbet <corbet@....net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Jeroen de Borst <jeroendb@...gle.com>,
	Praveen Kaligineedi <pkaligineedi@...gle.com>,
	Shailend Chand <shailend@...gle.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Willem de Bruijn <willemb@...gle.com>,
	David Ahern <dsahern@...nel.org>,
	Neal Cardwell <ncardwell@...gle.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	Shuah Khan <shuah@...nel.org>, sdf@...ichev.me,
	asml.silence@...il.com, dw@...idwei.uk,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Victor Nogueira <victor@...atatu.com>,
	Pedro Tammela <pctammela@...atatu.com>,
	Samiullah Khawaja <skhawaja@...gle.com>
Subject: Re: [PATCH net-next v4 5/9] net: add devmem TCP TX documentation

On Thu, Feb 20, 2025 at 02:09:10AM +0000, Mina Almasry wrote:
> +The user application must use MSG_ZEROCOPY flag when sending devmem TCP. Devmem
> +cannot be copied by the kernel, so the semantics of the devmem TX are similar
> +to the semantics of MSG_ZEROCOPY.
> +
> +	setsockopt(socket_fd, SOL_SOCKET, SO_ZEROCOPY, &opt, sizeof(opt));
> +
> +It is also recommended that the user binds the TX socket to the same interface
> +the dma-buf has been bound to via SO_BINDTODEVICE.
> +
> +	setsockopt(socket_fd, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname) + 1);
> +

Wrap both setsockopts above in literal code-block (just like other snippets
for consistency).

> +The user should create a msghdr where,
> +
> +iov_base is set to the offset into the dmabuf to start sending from.
> +iov_len is set to the number of bytes to be sent from the dmabuf.

Should above be bullet list?

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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