RE: [PATCH v9 2/4] ethdev: introduce protocol hdr based buffer split

["Ding, Xuan" <xuan.ding@intel.com>]

Hi Thomas,

> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Thursday, July 7, 2022 5:08 PM
> To: Wu, WenxuanX <wenxuanx.wu@intel.com>
> Cc: andrew.rybchenko@oktetlabs.ru; Li, Xiaoyun <xiaoyun.li@intel.com>;
> ferruh.yigit@xilinx.com; Singh, Aman Deep <aman.deep.singh@intel.com>;
> dev@dpdk.org; Zhang, Yuying <yuying.zhang@intel.com>; Zhang, Qi Z
> <qi.z.zhang@intel.com>; jerinjacobk@gmail.com;
> stephen@networkplumber.org; Wu, WenxuanX <wenxuanx.wu@intel.com>;
> Ding, Xuan <xuan.ding@intel.com>; Wang, YuanX <yuanx.wang@intel.com>;
> Ray Kinsella <mdr@ashroe.eu>
> Subject: Re: [PATCH v9 2/4] ethdev: introduce protocol hdr based buffer split
> 
> 13/06/2022 12:25, wenxuanx.wu@intel.com:
> > --- a/lib/ethdev/rte_ethdev.h
> > +++ b/lib/ethdev/rte_ethdev.h
> > @@ -1176,6 +1176,9 @@ struct rte_eth_txmode {
> >   *   specified in the first array element, the second buffer, from the
> >   *   pool in the second element, and so on.
> >   *
> > + * - The proto_hdrs in the elements define the split position of
> > + *   received packets.
> > + *
> >   * - The offsets from the segment description elements specify
> >   *   the data offset from the buffer beginning except the first mbuf.
> >   *   The first segment offset is added with RTE_PKTMBUF_HEADROOM.
> > @@ -1197,12 +1200,21 @@ struct rte_eth_txmode {
> >   *     - pool from the last valid element
> >   *     - the buffer size from this pool
> >   *     - zero offset
> > + *
> > + * - Length based buffer split:
> > + *     - mp, length, offset should be configured.
> > + *     - The proto_hdr field should not be configured.
> > + *
> > + * - Protocol header based buffer split:
> > + *     - mp, offset, proto_hdr should be configured.
> > + *     - The length field should not be configured.
> >   */
> >  struct rte_eth_rxseg_split {
> >  	struct rte_mempool *mp; /**< Memory pool to allocate segment
> from. */
> >  	uint16_t length; /**< Segment data length, configures split point. */
> >  	uint16_t offset; /**< Data offset from beginning of mbuf data buffer.
> */
> > -	uint32_t reserved; /**< Reserved field. */
> > +	/**< Supported ptypes mask of a specific pmd, configures split point.
> */
> 
> The doxygen syntax is wrong: remove the "<" which is for post-comment.

Thanks for your catch.

> 
> > +	uint32_t proto_hdr;
> >  };
> 
> How do we know it is a length or buffer split?
> Is it based on checking some 0 value?

Yes, as Andrew suggests, we introduced the API rte_eth_supported_hdrs_get() in v9.
It will report the driver supported protocol headers to be split.
If the API returns ENOTSUP, it means driver supports length based buffer split.

Of course, no matter what kind of buffer split it is, we need to check
RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT first.

Thanks,
Xuan

>