Re: [PATCH] app/testpmd: dump private info in 'show port info'

[Thomas Monjalon <thomas@monjalon.net>]

16/03/2023 11:46, Ferruh Yigit:
> On 3/16/2023I 9:19 AM, Dmitry Kozlyuk wrote:
> > On Thu, Mar 16, 2023 at 4:11 AM fengchengwen <fengchengwen@huawei.com> wrote:
> >> Because we have no API to know the PMD whether impl specific ops, we could only knowed by invoking.
> >> Except above impl, I also consider the other two:
> >> 1. just invoke rte_eth_dev_priv_dump without previous printf("Device private info") and later error printf.
> >>    and I think people may curious about the extra output without a prompt just like "Device private info".
> >> 2. use fmemopen (the below code), this way will perfect process the PMD which not imp ops.
> >>    FILE *f = fmemopen(buf, max-size(e.g. 128KB));
> >>    ret = rte_eth_dev_priv_dump(port_id, f);
> >>    if (ret == 0) {
> >>       printf("Device private info:\n");
> >>       printf("%s", buf);
> >>    }
> >>    But the windows platform don't support fmemopen.
> >>
> >> Hope for more feedback.
> > 
> > What if rte_eth_dev_priv_dump() was a documented no-op when "f == NULL"?
> > This can be implemented in ethdev layer:
> > 1) if not implemented, return ENOTSUP
> > 2) if f == NULL, return 0
> > 3) else call PMD
> > Technically, even now a null device handle can be used, but this is
> > cumbersome and wastes resources for running the API twice.
> 
> 
> Not sure about to overload "f == NULL" condition to detect the feature
> support.
> 
> It may be good to have a generic way to detect the support.
> 
> One way is to add new set of APIs just to test the dev_ops, and return
> boolean like:
> 'bool rte_eth_dev_is_priv_dump(uint16_t port_id);'
> 
> 
> Another option can be introducing an enum, each enum item can represent
> a dev_ops and a single API can be used to detect the support. This
> requires more maintenance for long term, as app needs to know more,
> not sure if I like this.
> 
> 
> If there is no objection to add new APIs, I can own the task, to have
> APIs like:
> 'bool rte_eth_dev_is_xxx(uint16_t port_id);'

That's a debug function, so I don't think we need to know in advance
whether it will print something or not.
Returning ENOTSUP should be enough in my opinion.