[RFC] ethdev: clarify rte_eth_tx_burst() return value and ownership semantics

[Andrew Rybchenko]

On 2/16/26 9:00 PM, Stephen Hemminger wrote:
> The documentation for rte_eth_tx_burst() uses the word "sent" to
> describe the return value, which is misleading. Packets returned as
> consumed may not have been transmitted yet; they have been accepted
> by the driver and are no longer the caller's responsibility.
> 
> This matters because the common usage pattern is:
> 
>      n = rte_eth_tx_burst(port, txq, mbufs, nb_pkts);
>      for (i = n; i < nb_pkts; i++)
>          rte_pktmbuf_free(mbufs[i]);
> 
> For this to work correctly, the contract must be:
>   - tx_pkts[0..n-1]: ownership transferred to the driver.
>   - tx_pkts[n..nb_pkts-1]: untouched, still owned by the caller.
> 
> Several drivers (and AI-assisted reviews) misinterpret the current
> wording and treat packets with errors as unconsumed, returning a
> short count. This causes callers to retry those packets indefinitely.
> The correct behavior is that the driver must consume (and free)
> erroneous packets, counting them via tx_errors.
> 
> Replace "sent" with "consumed" in the return value description,
> spell out the mbuf ownership contract, clarify the error handling
> expectation, and update the @return block to match.
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>

Acked-by: Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>

Thanks for the clarification. I really like it.