Re: [dpdk-dev] [PATCH 01/51] ethdev: change rte_eth_dev_info_get() return value to int

[Thomas Monjalon <thomas@monjalon.net>]

28/08/2019 16:39, Andrew Rybchenko:
> On 8/28/19 2:26 PM, Jan Viktorin wrote:
> > Andrew Rybchenko <arybchenko@solarflare.com> wrote:
> >> On 8/28/19 12:51 PM, Jan Viktorin wrote:
> >>> Andrew Rybchenko <arybchenko@solarflare.com> wrote:
> >>>> From: Ivan Ilchenko <Ivan.Ilchenko@oktetlabs.ru>
> >>>> + * @return
> >>>> + *   - (0) if successful.
> >>>> + *   - (-ENOTSUP) if support for dev_infos_get() does not exist
> >>>> for the device.
> >>> I believe that allowing PMDs to return -ENOTSUP is not a good idea.
> >>> At the moment, all PMDs provides this kind of information. It is not
> >>> always very reliable piece of information but for me, it is a piece
> >>> of gold I would not like to loose when configuring devices.
> >>>
> >>> I think it should be mandatory for all PMDs to provide this
> >>> function. Another possible way, give a sane default contents of
> >>> this structure. But, please, do not return -ENOTSUP.
> >> I agree that dev_infos_get() callback should be mandatory, but
> >> what the function should do if the callback is not provided?
> > One way would be to fail to register a PMD without that callback.
> > Such PMD driver would be simply wrong. This is what I mean by saying
> > "mandatory" - the callback MUST be provided.
> 
> Typically callbacks are set on probe and
> rte_eth_dev_pci_generic_probe() and similar functions could
> be updated to reject devices with missing dev_infos_get callback.
> However, there is a secondary process cases where dev_infos_get
> is not essential since control path may be unsupported in secondary
> process.
> 
> Anyway, I think it is a separate story.
> 
> > DPDK could be so nice to provide a default callback named like
> > default_dev_infos_get_when_you_are_incompetent_pmd_author() returning
> > mostly zeros and some always "known metadata" like device pointer,
> > driver_name, ...
> 
> Thomas, Ferruh, what do you think?

I like the idea of making some functions mandatory.
If we need to provide a default callback, why not.

I'm also thinking we need to better enforce a standardization
of basic features to be implemented. It would make DPDK more mature.