Re: [dpdk-dev] [PATCH 3/5] ethdev: allow iterating with only class filter

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 10/8/18 11:07 AM, Thomas Monjalon wrote:
> 08/10/2018 09:20, Andrew Rybchenko:
>> On 10/8/18 1:25 AM, Thomas Monjalon wrote:
>>> If no rte_device is given in the iterator,
>>> eth_dev_match() is looking at all ports without any restriction,
>>> except the ethdev kvargs filter.
>>>
>>> It allows to iterate with a devargs filter referencing only
>>> some ethdev parameters. The format (from the new devargs syntax) is:
>>> 	class=eth,paramY=Y
>>>
>>> Fixes: e815a7f69371 ("ethdev: register as a class")
>>>
>>> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
>>> ---
>>> --- a/lib/librte_ethdev/rte_class_eth.c
>>> +++ b/lib/librte_ethdev/rte_class_eth.c
>>> @@ -42,7 +42,7 @@ eth_dev_match(const struct rte_eth_dev *edev,
>>>    
>>>    	if (edev->state == RTE_ETH_DEV_UNUSED)
>>>    		return -1;
>>> -	if (edev->device != arg->device)
>>> +	if (arg->device != NULL && arg->device != edev->device)
>>>    		return -1;
>>>    	if (kvlist == NULL)
>>>    		/* Empty string matches everything. */
>> It looks like it is the only hunk which
>> Fixes: e815a7f69371 ("ethdev: register as a class")
> Yes this hunk is fixing above commit.
>
>> everything else adjusts the previous patch.
> Yes but the whole goal of this patch is to allow ethdev pure filter.
> All is related in this patch.
>
>> I think this fix should go before and the rest should be squashed
>> in the previous patch. It was really questionable why it is safe
>> to dereference iter->bus without checking that it is not NULL.
> No iter->bus was safe because iter->cls was checked before and
> implied that iter->bus was successfully set.

OK, I see now.

> I still think it is better for understanding to split different
> kind of filters in 2 patches.
> I may remove the Fixes line however. Opinion?

Yes, it makes sense. If so, I think it is better to remove Fixes line.
With Fixes I would expect to be able to apply it before previous patch.

> [...]
>>> +	/* Handle a case from future syntax, without any bus-level argument. */
>>> +	if (strncmp(devargs_str, iter_anybus_str,
>>> +			strlen(iter_anybus_str)) == 0) {
>>> +		iter->cls_str = devargs_str + strlen(iter_anybus_str);
>>> +		goto end;
>>> +	}
>>> +
>> It looks like a hack, but I guess we need it since rte_devargs_parse()
>> cannot handle the case. May be it is acceptable if we have no time
>> to solve it, but it would be good to highlight it better in the comments.
> This function is a mix of old and new syntax.
> When only new syntax will be supported, it will be better.
> It is a work in progress.
> I do not know how to better explain it.

I'd suggest to highligh rte_devargs_parse() limitations here to
explain why special handling is required here.