[ptxdist] How to express a dependency that can be satisfied by alternative packages

[ptxdist] How to express a dependency that can be satisfied by alternative packages

[Guillermo Rodriguez Garcia]

Hi all,

Let's say I have a package that requires a specific cmd line utility
(e.g. openvt).
This can be provided by two different packages (e.g. busybox or kbd)
How to express that dependency in the .in file of my package ?

Thanks,

Guillermo Rodriguez Garcia
guille.rodriguez@gmail.com

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Re: [ptxdist] How to express a dependency that can be satisfied by alternative packages

[Roland Hieber]

On Mon, Dec 16, 2019 at 07:23:13PM +0100, Guillermo Rodriguez Garcia wrote:
> Hi all,
> 
> Let's say I have a package that requires a specific cmd line utility
> (e.g. openvt).
> This can be provided by two different packages (e.g. busybox or kbd)
> How to express that dependency in the .in file of my package ?

PTXdist (or rather kconfig) does not have a notion of "provides" or
metapackages. I think is currently no way other than making a choice
option that selects the one or the other, or letting your config option
deoend on BUSYBOX_OPENVT || KBD_OPENVT. In the latter case it is
probably good to add a comment above it that depends on the opposite
value notifying the user that neither one of them is selected (see the
comment above IPTABLES_INSTALL_IPTABLES_APPLY in iptables.in for
example).

 - Roland

-- 
Roland Hieber, Pengutronix e.K.          | r.hieber@pengutronix.de     |
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31137 Hildesheim, Germany                | Phone: +49-5121-206917-0    |
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Re: [ptxdist] How to express a dependency that can be satisfied by alternative packages

[Michael Olbrich]

Hi,

On Thu, Jan 02, 2020 at 12:53:36PM +0100, Roland Hieber wrote:
> On Mon, Dec 16, 2019 at 07:23:13PM +0100, Guillermo Rodriguez Garcia wrote:
> > Let's say I have a package that requires a specific cmd line utility
> > (e.g. openvt).
> > This can be provided by two different packages (e.g. busybox or kbd)
> > How to express that dependency in the .in file of my package ?
> 
> PTXdist (or rather kconfig) does not have a notion of "provides" or
> metapackages. I think is currently no way other than making a choice
> option that selects the one or the other, or letting your config option
> deoend on BUSYBOX_OPENVT || KBD_OPENVT. In the latter case it is
> probably good to add a comment above it that depends on the opposite
> value notifying the user that neither one of them is selected (see the
> comment above IPTABLES_INSTALL_IPTABLES_APPLY in iptables.in for
> example).

Actually, the correct way to do this is probably:

	select KBD		if !BUSYBOX_OPENVT && RUNTIME
	select KBD_OPENVT	if !BUSYBOX_OPENVT && RUNTIME

rules/openvpn.in or rules/easy-rsa.in already do something like this.

Using 'depends' is not really a good idea. It hides options and can cause
Dependency Chains that cannot be resolved automatically.

Michael

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [ptxdist] How to express a dependency that can be satisfied by alternative packages

[Guillermo Rodriguez Garcia]

El jue., 2 ene. 2020 a las 16:15, Michael Olbrich
(<m.olbrich@pengutronix.de>) escribió:
>
> Hi,
>
> On Thu, Jan 02, 2020 at 12:53:36PM +0100, Roland Hieber wrote:
> > On Mon, Dec 16, 2019 at 07:23:13PM +0100, Guillermo Rodriguez Garcia wrote:
> > > Let's say I have a package that requires a specific cmd line utility
> > > (e.g. openvt).
> > > This can be provided by two different packages (e.g. busybox or kbd)
> > > How to express that dependency in the .in file of my package ?
> >
> > PTXdist (or rather kconfig) does not have a notion of "provides" or
> > metapackages. I think is currently no way other than making a choice
> > option that selects the one or the other, or letting your config option
> > deoend on BUSYBOX_OPENVT || KBD_OPENVT. In the latter case it is
> > probably good to add a comment above it that depends on the opposite
> > value notifying the user that neither one of them is selected (see the
> > comment above IPTABLES_INSTALL_IPTABLES_APPLY in iptables.in for
> > example).
>
> Actually, the correct way to do this is probably:
>
>         select KBD              if !BUSYBOX_OPENVT && RUNTIME
>         select KBD_OPENVT       if !BUSYBOX_OPENVT && RUNTIME

What is exactly the meaning of RUNTIME? Why is it needed here?

Apart from that. What about the following:

select KBD            if !BUSYBOX
select KBD_OPENVT     if !BUSYBOX
select BUSYBOX_OPENVT if BUSYBOX && !KBD_OPENVT

This would prefer the Busybox version of openvt if none is explicitly
selected and Busybox is already present (thus avoiding to pull in the
kbd package if we can avoid it)

Best,

Guillermo Rodriguez Garcia
guille.rodriguez@gmail.com

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Re: [ptxdist] How to express a dependency that can be satisfied by alternative packages

[Michael Olbrich]

On Tue, Jan 07, 2020 at 12:11:19PM +0100, Guillermo Rodriguez Garcia wrote:
> El jue., 2 ene. 2020 a las 16:15, Michael Olbrich
> (<m.olbrich@pengutronix.de>) escribió:
> > On Thu, Jan 02, 2020 at 12:53:36PM +0100, Roland Hieber wrote:
> > > On Mon, Dec 16, 2019 at 07:23:13PM +0100, Guillermo Rodriguez Garcia wrote:
> > > > Let's say I have a package that requires a specific cmd line utility
> > > > (e.g. openvt).
> > > > This can be provided by two different packages (e.g. busybox or kbd)
> > > > How to express that dependency in the .in file of my package ?
> > >
> > > PTXdist (or rather kconfig) does not have a notion of "provides" or
> > > metapackages. I think is currently no way other than making a choice
> > > option that selects the one or the other, or letting your config option
> > > deoend on BUSYBOX_OPENVT || KBD_OPENVT. In the latter case it is
> > > probably good to add a comment above it that depends on the opposite
> > > value notifying the user that neither one of them is selected (see the
> > > comment above IPTABLES_INSTALL_IPTABLES_APPLY in iptables.in for
> > > example).
> >
> > Actually, the correct way to do this is probably:
> >
> >         select KBD              if !BUSYBOX_OPENVT && RUNTIME
> >         select KBD_OPENVT       if !BUSYBOX_OPENVT && RUNTIME
> 
> What is exactly the meaning of RUNTIME? Why is it needed here?

This means, that kbd is only needed at runtime and not at buildtime. This
relaxes the build dependencies a bit and allows more parallelization.
It's really only needed for the first line, but we add it to both for
consistency reasons.

> Apart from that. What about the following:
> 
> select KBD            if !BUSYBOX
> select KBD_OPENVT     if !BUSYBOX
> select BUSYBOX_OPENVT if BUSYBOX && !KBD_OPENVT
> 
> This would prefer the Busybox version of openvt if none is explicitly
> selected and Busybox is already present (thus avoiding to pull in the
> kbd package if we can avoid it)

Does that work? kconfig sometimes produces circular dependency errors, even
if they don't really exist.
If it works, then that's ok too (with the '&& RUNTIME' added).

Michael

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [ptxdist] How to express a dependency that can be satisfied by alternative packages

[Guillermo Rodriguez Garcia]

El mar., 7 ene. 2020 a las 12:29, Michael Olbrich
(<m.olbrich@pengutronix.de>) escribió:
>
> On Tue, Jan 07, 2020 at 12:11:19PM +0100, Guillermo Rodriguez Garcia wrote:
> > El jue., 2 ene. 2020 a las 16:15, Michael Olbrich
> > (<m.olbrich@pengutronix.de>) escribió:
> > > On Thu, Jan 02, 2020 at 12:53:36PM +0100, Roland Hieber wrote:
> > > > On Mon, Dec 16, 2019 at 07:23:13PM +0100, Guillermo Rodriguez Garcia wrote:
> > > > > Let's say I have a package that requires a specific cmd line utility
> > > > > (e.g. openvt).
> > > > > This can be provided by two different packages (e.g. busybox or kbd)
> > > > > How to express that dependency in the .in file of my package ?
> > > >
> > > > PTXdist (or rather kconfig) does not have a notion of "provides" or
> > > > metapackages. I think is currently no way other than making a choice
> > > > option that selects the one or the other, or letting your config option
> > > > deoend on BUSYBOX_OPENVT || KBD_OPENVT. In the latter case it is
> > > > probably good to add a comment above it that depends on the opposite
> > > > value notifying the user that neither one of them is selected (see the
> > > > comment above IPTABLES_INSTALL_IPTABLES_APPLY in iptables.in for
> > > > example).
> > >
> > > Actually, the correct way to do this is probably:
> > >
> > >         select KBD              if !BUSYBOX_OPENVT && RUNTIME
> > >         select KBD_OPENVT       if !BUSYBOX_OPENVT && RUNTIME
> >
> > What is exactly the meaning of RUNTIME? Why is it needed here?
>
> This means, that kbd is only needed at runtime and not at buildtime. This
> relaxes the build dependencies a bit and allows more parallelization.
> It's really only needed for the first line, but we add it to both for
> consistency reasons.
>
> > Apart from that. What about the following:
> >
> > select KBD            if !BUSYBOX
> > select KBD_OPENVT     if !BUSYBOX
> > select BUSYBOX_OPENVT if BUSYBOX && !KBD_OPENVT
> >
> > This would prefer the Busybox version of openvt if none is explicitly
> > selected and Busybox is already present (thus avoiding to pull in the
> > kbd package if we can avoid it)
>
> Does that work? kconfig sometimes produces circular dependency errors, even
> if they don't really exist.
> If it works, then that's ok too (with the '&& RUNTIME' added).

Uhm, indeed Kconfig complains.

What would then be the way to achieve this:
- If busybox is selected, then select BUSYBOX_OPENVT, unless
KBD_OPENVT is already selected
- If busybox is NOT selected, then select KBD_OPENVT
?

The closest I've got is this:

select KBD            if !BUSYBOX
select KBD_OPENVT     if !BUSYBOX
select BUSYBOX_OPENVT if BUSYBOX

But this will end up selecting both versions of openvt if KBD_OPENVT
was already selected...

Guillermo

-- 
Guillermo Rodriguez Garcia
guille.rodriguez@gmail.com

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