[dpdk-dev] [PATCH v8 1/6] ethdev: introduce Rx buffer split

[Thomas Monjalon]

16/10/2020 11:15, Slava Ovsiienko:
> From: Andrew Rybchenko <arybchenko at solarflare.com>
> > On 10/16/20 10:48 AM, Viacheslav Ovsiienko wrote:
> > >  /**
> > > + * Ethernet device Rx buffer segmentation capabilities.
> > > + */
> > > +__extension__
> > > +struct rte_eth_rxseg_capa {
> > > +	uint16_t max_seg; /**< Maximum amount of segments to split. */
> > 
> > May be 'max_segs' to avoid confusing vs maximum segment length.
> > 
> OK, max_nseg would be more appropriate.
> 
> > > +	uint16_t multi_pools:1; /**< Supports receiving to multiple pools.*/
> > > +	uint16_t offset_allowed:1; /**< Supports buffer offsets. */
> > > +	uint16_t offset_align_log2:4; /**< Required offset alignment. */
> > 
> > 4 bits are even insufficient to specify cache-line alignment.
> > IMHO at least 8 bits are required.
> 
> 4 bits seems to be quite sufficient. It is a log2, tells how many lsbs in offset should be zeroes.
> 2^15 is 32K, it covers all reasonable alignments for uint16_t type.

bitfields with uint16_t is not standard I think,
we could experience build issues.
If I remember well uint32_t is safer.