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

[Dmitry Kozlyuk]

On Thu, Mar 16, 2023 at 4:11 AM fengchengwen <fengchengwen at 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.