Hi,
I'm currently porting an application to the new ethdev offload api,
and I have two questions about it.
1/ inconsistent offload capa for PMDs using the old API?
It is stated in struct rte_eth_txmode:
/**
* Per-port Tx offloads to be set using DEV_TX_OFFLOAD_* flags.
* Only offloads set on tx_offload_capa field on rte_eth_dev_info
* structure are allowed to be set.
*/
uint64_t offloads;
So, if I want to enable DEV_TX_OFFLOAD_MULTI_SEGS for the whole ethdev,
I must check that DEV_TX_OFFLOAD_MULTI_SEGS is advertised in
dev_info->tx_offload_capa.
In my understanding, many PMDs are still using the old API, and there is
a conversion layer in ethdev when doing dev_configure(). But I don't see
any similar mechanism for the dev_info. Therefore,
DEV_TX_OFFLOAD_MULTI_SEGS is not present in tx_offload_capa, and if I
follow the API comment, I'm not allowed to use this feature.
Am I missing something or is it a bug?
It looks that testpmd does not check the capa before setting the an
offload flag. This could be a workaround in my application.
2/ meaning of rxmode.jumbo_frame, rxmode.enable_scatter, rxmode.max_rx_pkt_len
While it's not related to the new API, it is probably a good opportunity
to clarify the meaning of these flags. I'm not able to find a good
documentation about them.
Here is my understanding, the configuration only depends on:
- the maximum rx frame length
- the amount of data available in a mbuf (minus headroom)
Flags to set in rxmode (example):
+---------------+----------------+----------------+-----------------+
| |mbuf_data_len=1K|mbuf_data_len=2K|mbuf_data_len=16K|
+---------------+----------------+----------------+-----------------+
|max_rx_len=1500|enable_scatter | | |
+---------------+----------------+----------------+-----------------+
|max_rx_len=9000|enable_scatter, |enable_scatter, |jumbo_frame |
| |jumbo_frame |jumbo_frame | |
+---------------+----------------+----------------+-----------------+
If this table is correct, the flag jumbo_frame would be equivalent to
check if max_rx_pkt_len is above a threshold.
And enable_scatter could be deduced from the mbuf size of the given rxq
(which is a bit harder but maybe doable).
Thanks,
Olivier
