From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [PATCH v5 1/2] ethdev: introduce generic IP/UDP
	tunnel checksum and TSO
Date: Tue, 17 Apr 2018 23:21:55 +0200
Message-ID: <3801247.KLjoC6WWjY@xps>
References: <20180408123240.110698-1-xuemingl@mellanox.com>
 <20180417144759.160311-1-xuemingl@mellanox.com>
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Cc: dev@dpdk.org, Wenzhuo Lu <wenzhuo.lu@intel.com>,
 Jingjing Wu <jingjing.wu@intel.com>, Yongseok Koh <yskoh@mellanox.com>,
 Olivier MATZ <olivier.matz@6wind.com>, Shahaf Shuler <shahafs@mellanox.com>,
 Bernard <bernard.iremonger@intel.com>, Ferruh Yigit <ferruh.yigit@intel.com>
To: Xueming Li <xuemingl@mellanox.com>
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17/04/2018 16:47, Xueming Li:
> This patch introduce new TX offload flags for device that supports
> IP or UDP tunneled packet L3/L4 checksum and TSO offload.
> 
> The support from the device is for inner and outer checksums on
> IPV4/TCP/UDP and TSO for *any packet with the following format*:
> 
> <some headers> / [optional IPv4/IPv6] / [optional TCP/UDP] / <some
> headers> / [optional inner IPv4/IPv6] / [optional TCP/UDP]
> 
> For example the following packets can use this feature:
> 
> 1. eth / ipv4 / udp / VXLAN / ip / tcp
> 2. eth / ipv4 / GRE / MPLS / ipv4 / udp
> 
> Please note that tunnel headers that contain payload length, sequence id
> or checksum will not be updated.
[...]
> +/**< Device supports UDP tunneled packet TSO */
> +#define DEV_TX_OFFLOAD_UDP_TNL_TSO      0x00040000
> +/**< Device supports IP based tunnel packet TSO */
> +#define DEV_TX_OFFLOAD_IP_TNL_TSO       0x00080000

These doxygen comments are related to the constants on the next line.
So the syntax is /** not /**<

[...]

General comment: API description is required for application writers
and PMD developers. You need to provide details about what the offload
is expected to do.

> +/**
> + * Generic IP encapsulated tunnel type, used for TSO offload instead
> + * of defining new tunnel types.

The words "instead of defining new tunnel types" are justifications for
the commit message, not for the code itself.

> This feature relies on offloading
> + * DEV_TX_OFFLOAD_IP_TNL_TSO present.

I think you want to say that DEV_TX_OFFLOAD_IP_TNL_TSO must be enabled.

> + * Tunnel header that contains payload length, sequence id or checksum
> + * is not expected to be updated.

OK
So what is updated by this offload exactly?
inner and outer checksums on IPV4/TCP/UDP? What else?
No IPv6? No SCTP?

> + */
> +#define PKT_TX_TUNNEL_IP (0xDULL << 45)
> +/**
> + * Generic UDP encapsulated tunnel type, used for TSO offload instead
> + * of defining new tunnel types. This feature relies on offloading
> + * DEV_TX_OFFLOAD_UDP_TNL_TSO present.
> + * Tunnel header that contains payload length, sequence id or checksum
> + * is not expected to be updated.
> + */

Same comments as for PKT_TX_TUNNEL_IP.

> +#define PKT_TX_TUNNEL_UDP (0xEULL << 45)