From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas.monjalon@6wind.com>
Subject: Re: [PATCH v12 1/6] ethdev: add Tx preparation
Date: Thu, 01 Dec 2016 17:28:52 +0100
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Cc: dev@dpdk.org, konstantin.ananyev@intel.com, olivier.matz@6wind.com
To: Tomasz Kulasek <tomaszx.kulasek@intel.com>
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2016-11-23 18:36, Tomasz Kulasek:
> +/**
> + * Process a burst of output packets on a transmit queue of an Ethernet device.
> + *
> + * The rte_eth_tx_prepare() function is invoked to prepare output packets to be
> + * transmitted on the output queue *queue_id* of the Ethernet device designated
> + * by its *port_id*.
> + * The *nb_pkts* parameter is the number of packets to be prepared which are
> + * supplied in the *tx_pkts* array of *rte_mbuf* structures, each of them
> + * allocated from a pool created with rte_pktmbuf_pool_create().
> + * For each packet to send, the rte_eth_tx_prepare() function performs
> + * the following operations:
> + *
> + * - Check if packet meets devices requirements for tx offloads.
> + *
> + * - Check limitations about number of segments.
> + *
> + * - Check additional requirements when debug is enabled.
> + *
> + * - Update and/or reset required checksums when tx offload is set for packet.
> + *
> + * Since this function can modify packet data, provided mbufs must be safely
> + * writable (e.g. modified data cannot be in shared segment).

I think we will have to remove this limitation in next releases.
As we don't know how it could affect the API, I suggest to declare this
API EXPERIMENTAL.