Re: [dpdk-dev] [PATCH] ethdev: support queue-based priority flow control

[Jerin Jacob <jerinjacobk@gmail.com>]

On Sat, Dec 4, 2021 at 11:08 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Sat, 4 Dec 2021 22:54:58 +0530
> <jerinj@marvell.com> wrote:
>
> > +     /**
> > +      * Maximum supported traffic class as per PFC (802.1Qbb) specification.
> > +      *
> > +      * Based on device support and use-case need, there are two different
> > +      * ways to enable PFC. The first case is the port level PFC
> > +      * configuration, in this case, rte_eth_dev_priority_flow_ctrl_set()
> > +      * API shall be used to configure the PFC, and PFC frames will be
> > +      * generated using based on VLAN TC value.
> > +      * The second case is the queue level PFC configuration, in this case,
> > +      * Any packet field content can be used to steer the packet to the
> > +      * specific queue using rte_flow or RSS and then use
> > +      * rte_eth_dev_priority_flow_ctrl_queue_set() to set the TC mapping
> > +      * on each queue. Based on congestion selected on the specific queue,
> > +      * configured TC shall be used to generate PFC frames.
> > +      *
> > +      * When set to non zero value, application must use queue level
> > +      * PFC configuration via rte_eth_dev_priority_flow_ctrl_queue_set() API
> > +      * instead of port level PFC configuration via
> > +      * rte_eth_dev_priority_flow_ctrl_set() API to realize
> > +      * PFC configuration.
> > +      */
> > +     uint8_t pfc_queue_tc_max;
> > +     uint8_t reserved_8s[7];
> > +     uint64_t reserved_64s[1]; /**< Reserved for future fields */
> >       void *reserved_ptrs[2];   /**< Reserved for future fields */
>
> Not sure you can claim ABI compatibility because the previous versions of DPDK
> did not enforce that reserved fields must be zero.  The Linux kernel
> learned this when adding flags for new system calls; reserved fields only
> work if you enforce that application must set them to zero.

In this case it rte_eth_dev_info is an out parameter and implementation of
rte_eth_dev_info_get() already memseting to 0.
Do you still see any other ABI issue?

See rte_eth_dev_info_get()
        /*
         * Init dev_info before port_id check since caller does not have
         * return status and does not know if get is successful or not.
         */
        memset(dev_info, 0, sizeof(struct rte_eth_dev_info));