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

[Thomas Monjalon <thomas@monjalon.net>]

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.

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?

[...]
> > +	/* 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.