[dpdk-dev] [RFC 2/2] librte_ether: add new fields to rte_eth_dev_info struct

[Ananyev, Konstantin]

Hi everyone,

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Thomas Monjalon
> Sent: Friday, April 15, 2016 11:36 AM
> To: Pattan, Reshma
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [RFC 2/2] librte_ether: add new fields to rte_eth_dev_info struct
> 
> 2016-04-14 10:44, Reshma Pattan:
> > --- a/lib/librte_ether/rte_ethdev.h
> > +++ b/lib/librte_ether/rte_ethdev.h
> > @@ -908,6 +908,9 @@ struct rte_eth_dev_info {
> >  	struct rte_eth_desc_lim rx_desc_lim;  /**< RX descriptors limits */
> >  	struct rte_eth_desc_lim tx_desc_lim;  /**< TX descriptors limits */
> >  	uint32_t speed_capa;  /**< Supported speeds bitmap (ETH_LINK_SPEED_). */
> > +	/** number of queues configured by software*/
> > +	uint16_t nb_rx_queues; /**< Number of RX queues. */
> > +	uint16_t nb_tx_queues; /**< Number of TX queues. */
> >  };
> 
> I think the ethdev design is strange for these structures.
> struct rte_eth_dev is internal to be used inside the ethdev API
> or by the drivers.
> It contains struct rte_eth_dev_data which can be of interest for
> the application, except the dev_private part (which could be
> directly in struct rte_eth_dev).
> 
> So the global question is: how to share the device data with the
> application?
> Instead of giving a pointer or a copy of struct rte_eth_dev_data,
> we have some different accessors:
> 	- rte_eth_dev_info_get() with a specific struct rte_eth_dev_info
> which gathers a lot of info, not only from struct rte_eth_dev_data
> 	- rte_eth_macaddr_get()
> 	- rte_eth_dev_socket_id()
> 	- rte_eth_link_get() which is more than an accessor
> 
> I think having some specialized accessors is good.
> But the rte_eth_dev_info_get() looks like to be a big request
> without precise goal and going to break ABI really often.
> There are some queues informations, some (not so precise)
> offload capabilities, some steering (RSS/VMDq) informations,
> the default configuration of some Intel NIC thresholds,
> the speed capabilities, etc.
> 
> Shouldn't we try to streamline this API?

I think in general it is a good idea  to split dev_info into some smaller sub-pieces.
But introduce a new API just for these 2 fields seems like an overkill to me.
My vote would be to allow nb_rx/tx_queues into dev_info,
If we'll decide to split dev_info - I think it needs to be a subject for a separate   
patch/discussion.
Konstantin