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To: Shreyansh Jain <shreyansh.jain@nxp.com>
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From: Ferruh Yigit <ferruh.yigit@intel.com>
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Date: Thu, 28 Sep 2017 00:37:13 +0100
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Subject: Re: [dpdk-dev] [PATCH v4 41/41] net/dpaa: support for extended
statistics
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On 9/27/2017 9:26 AM, Shreyansh Jain wrote:
> On Thursday 21 September 2017 06:56 PM, Shreyansh Jain wrote:
>> On Monday 18 September 2017 08:27 PM, Ferruh Yigit wrote:
>>> On 9/9/2017 12:21 PM, Shreyansh Jain wrote:
>>>> From: Hemant Agrawal <hemant.agrawal@nxp.com>
>>>>
>>>> Signed-off-by: Hemant Agrawal <hemant.agrawal@nxp.com>
>>>
>>> <...>
>>>
>>>> +static int
>>>> +dpaa_dev_xstats_get(struct rte_eth_dev *dev, struct rte_eth_xstat
>>>> *xstats,
>>>> + unsigned int n)
>>>> +{
>>>> + struct dpaa_if *dpaa_intf = dev->data->dev_private;
>>>> + unsigned int i = 0, num = RTE_DIM(dpaa_xstats_strings);
>>>> + uint64_t values[sizeof(struct dpaa_if_stats) / 8];
>>>> +
>>>> + if (xstats == NULL)
>>>> + return 0;
>>>
>>> This is a little not clear from API definition, but I guess when xstats
>>> is NULL, it should return num of available stats, "num" for this case. I
>>> guess there are PMDs implements both, can you please double check?
>>
>> Ok. I will check again.
>
> I checked a number of other ethev implementations. Some like i40e/e1000
> also return 0 when xstats is NULL. Others, like bnx2x and qede don't
> handle this situation.
> All return "num" when passed argument is larger than number of elements
> in the table.
>
> Though, I think the logic that get_xstats should return its size (num)
> when passed with NULL, looks good to me.
> How does one standardize such semantics for existing APIs?
Thanks for checking, I guess first we should clarify the API and the
expected behavior [1] and later update required PMDs.
So for now I think PMD is OK as it is.
[1]
I double checked the rte_eth_xstats_get(). It does:
If xstats == NULL
xcount = dev_ops->xstats_get(dev, NULL, 0);
return count + xcount;
Intention looks like to returning number of available stats, otherwise
returning "count + 0" will be useless.
So it looks like expectation from eth_xstats_get_t for that case is
returning xstats size, but this not clear and not documented in API comment.
>
> (I can add this info to the API document that you created - but only
> once we know if others will agree to change)
>
>>
>>>
>>>> +
>>>> + if (n < num)
>>>> + return num;
>>>> +
>>>> + fman_if_stats_get_all(dpaa_intf->fif, values,
>>>> + sizeof(struct dpaa_if_stats) / 8);
>>>> +
>>>> + for (i = 0; i < num; i++) {
>>>> + xstats[i].id = i;
>>>> + xstats[i].value = values[dpaa_xstats_strings[i].offset / 8];
>>>> + }
>>>> + return i;
>>>> +}
>>>
>>> <...>
>>>
>>
>>
>