[dpdk-dev] [PATCH v4 2/2] ethdev: get the supported pools for a port

[santosh]

Hi Olivier,


On Monday 25 September 2017 10:52 PM, santosh wrote:
> Hi Olivier,
>
>
> On Monday 25 September 2017 08:37 AM, Olivier MATZ wrote:
>>> +{
>>> +	struct rte_eth_dev *dev;
>>> +	const char *tmp;
>>> +
>>> +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
>>> +
>>> +	if (pool == NULL)
>>> +		return -EINVAL;
>>> +
>>> +	dev = &rte_eth_devices[port_id];
>>> +
>>> +	if (*dev->dev_ops->pools_ops_supported == NULL) {
>>> +		tmp = rte_eal_mbuf_default_mempool_ops();
>>> +		if (!strcmp(tmp, pool))
>>> +			return 0;
>>> +		else
>>> +			return -ENOTSUP;
>> I don't understand why we are comparing with
>> rte_eal_mbuf_default_mempool_ops().
>>
>> It means that the result of the function would be influenced
>> by the parameter given by the user.
> But that will be only for ops not supported case and in that case,
> function _must_ make sure that if inputted param is _default_ops_name
> then function should return ops supported correct info (whether 
> returning '0' : Best ops or '1': ops does support 
> , this part is arguable.. meaning One can say that default_ops ='handle-name' is best possible handle Or 
> one of handle which platform supports).
>
>> I think that a PMD that does not implement ->pools_ops_supported
>> should always return 1 (mempool is supported).
> Return 1 says: PMD support this ops.. 
>
> So if ops is not supported and func returns with 1, then which ops application will use?
> If that ops is default_ops.. then How application will distinguish when to use default ops or
> param ops?.. as because in both cases func will return with value 1.
>
> The approach in the patch takes care of that condition and func will return -ENOTSUP 
> if (ops not support || inputted param not matching with default ops) otherwise will return
> 0 or 1.
>
> At application side; 
> For error case: In case of -ENOTSUP, its upto application to use _default_ops or exit.
> For good case: 0 or 1 case, func gaurantee that handle is either best handle for pool or pool supports
> that handle.. However in your suggestion if ops not supported case returns 1 then application is not 
> sure which ops to use.. default_ops Or input ops given to func.
>
> make sense? 

Ping? Are you fine with said explanation if not then would you
share your thought in case if ops not supported returns simply
1 if then how application differentiate whether to use
default_ops Or inputted param ops.. as return value 1 holds true
for both cases, so how application will pick and choose which ops
to use?

Can we pl. close on this? need to send v5 for -rc1 release.

Thanks.