Re: [dpdk-dev] [PATCH] ethdev: add queue state when retrieve queue information

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Andrew Rybchenko
> Sent: Monday, March 22, 2021 2:49 PM
> To: Yigit, Ferruh <ferruh.yigit@intel.com>; Lijun Ou <oulijun@huawei.com>; thomas@monjalon.net
> Cc: dev@dpdk.org; linuxarm@openeuler.org; Andrew Rybchenko <arybchenko@solarflare.com>; David Marchand
> <david.marchand@redhat.com>; Ray Kinsella <mdr@ashroe.eu>; Luca Boccassi <bluca@debian.org>
> Subject: Re: [dpdk-dev] [PATCH] ethdev: add queue state when retrieve queue information
> 
> On 3/22/21 12:22 PM, Ferruh Yigit wrote:
> > On 3/18/2021 12:25 PM, Lijun Ou wrote:
> >> Currently, upper-layer application could get queue state only
> >> through pointers such as dev->data->tx_queue_state[queue_id],
> >> this is not the recommended way to access it. So this patch
> >> add get queue state when call rte_eth_rx_queue_info_get and
> >> rte_eth_tx_queue_info_get API.
> >>
> >> Note: The hairpin queue is not supported with above
> >> rte_eth_*x_queue_info_get, so the queue state could be
> >> RTE_ETH_QUEUE_STATE_STARTED or RTE_ETH_QUEUE_STATE_STOPPED.
> >> Note: After add queue_state field, the 'struct rte_eth_rxq_info' size
> >> remains 128B, and the 'struct rte_eth_txq_info' size remains 64B, so
> >> it could be ABI compatible.
> >>
> >> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> >> Signed-off-by: Lijun Ou <oulijun@huawei.com>
> >
> > <...>
> >
> >> diff --git a/lib/librte_ethdev/rte_ethdev.h
> >> b/lib/librte_ethdev/rte_ethdev.h
> >> index efda313..3b83c5a 100644
> >> --- a/lib/librte_ethdev/rte_ethdev.h
> >> +++ b/lib/librte_ethdev/rte_ethdev.h
> >> @@ -1591,6 +1591,8 @@ struct rte_eth_rxq_info {
> >>       uint8_t scattered_rx;       /**< scattered packets RX supported. */
> >>       uint16_t nb_desc;           /**< configured number of RXDs. */
> >>       uint16_t rx_buf_size;       /**< hardware receive buffer size. */
> >> +    /**< Queues state: STARTED(1) / STOPPED(0). */
> >> +    uint8_t queue_state;
> >>   } __rte_cache_min_aligned;
> >>     /**
> >> @@ -1600,6 +1602,8 @@ struct rte_eth_rxq_info {
> >>   struct rte_eth_txq_info {
> >>       struct rte_eth_txconf conf; /**< queue config parameters. */
> >>       uint16_t nb_desc;           /**< configured number of TXDs. */
> >> +    /**< Queues state: STARTED(1) / STOPPED(0). */
> >> +    uint8_t queue_state;
> >>   } __rte_cache_min_aligned;
> >>     /* Generic Burst mode flag definition, values can be ORed. */
> >>
> >
> > This is causing an ABI warning [1], but I guess it is safe since the
> > size of the struct is not changing (cache align). Adding a few more
> > people to comment.
> >
> >
> > [1]
> > https://travis-ci.com/github/ovsrobot/dpdk/builds/220497651
> 
> Frankly speaking I dislike addition of queue_state as uint8_t.
> IMHO it should be either 'bool started' or enum to support more
> states in the future if we need.

I think we already have set of defines for it:
lib/librte_ethdev/rte_ethdev_driver.h:925:#define RTE_ETH_QUEUE_STATE_STOPPED 0
lib/librte_ethdev/rte_ethdev_driver.h:926:#define RTE_ETH_QUEUE_STATE_STARTED 1
lib/librte_ethdev/rte_ethdev_driver.h:927:#define RTE_ETH_QUEUE_STATE_HAIRPIN 2

If we want to publish it, then might be enough just move these macros to rte_ethdev.h or so.

About uint8_t vs enum - yes, in principle enum would be a bit nicer,
but right now rte_eth_dev_data.(rx|tx)_queue_state[]  itself is an array of uint8_t.
So probably not much point to waste extra 3B in rte_eth_(rxq|txq)_info.
Unless in future will want to change it in struct rte_eth_dev_data too
(or even hide it inside dev private queue data).