Re: [OE-core] why "PREFERRED_PROVIDER_udev" and not "PREFERRED_PROVIDER_virtual/udev"?

["Robert P. J. Day" <rpjday@crashcourse.ca>]

On Mon, 30 Aug 2021, Robert P. J. Day wrote:

>   i was going to extend section 3.3.17, "Using Virtual Providers",
> with an intro example using "udev" until i realized that that
> example doesn't use the "virtual/" notation. so ... why not? is
> there some distinction between other components that use the
> "virtual/" prefix, but a reason that one does not specify:
>
>   PROVIDES = "virtual/udev"
>
> rather than just:
>
>   PROVIDES = "udev"
>
> and then use the corresponding PREFERRED_PROVIDER_virtual/udev
> notation?

  just to make sure folks understand what i'm getting at, the section:

https://docs.yoctoproject.org/dev-manual/common-tasks.html#using-virtual-providers

opens with, "Prior to a build, if you know that several different
recipes provide the same functionality, you can use a virtual provider
(i.e. virtual/*) as a placeholder for the actual provider."

  except there are cases where several different recipes provide the
same functionality that *don't* incorporate the "virtual/" notation,
so which ones merit that and which ones don't? (i mentioned "udev"
being provided by both "eudev" and "systemd", for which i wrote an
utterly brilliant explanation that i now realize isn't appropriate for
that section.)

  in the simpler cases, you have recipes that have a new name that
can now be used in place of the old, such that "stress-ng" provides
"stress", so you don't have to mess with all your old images and
packagegroups. and in situations like that, the "virtual/" notation
would seem out of place.

  OTOH, well, virtual "kernel" and "bootloader" makes perfect sense as
they represent a more abstract idea. so ... thoughts? even though
"udev" does not use the "virtual/" notation, would it still fall under
the category of "virtual provider"? if not, how would one describe it?

rday