linux-kernel - Re: [PATCH net] net: enetc: fix the netc-lib driver build dependency

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Message-ID: <20250604091111.oo2o2xd2zeqqisaf@skbuf>
Date: Wed, 4 Jun 2025 12:11:11 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Wei Fang <wei.fang@....com>, Claudiu Manoil <claudiu.manoil@....com>,
	Clark Wang <xiaoning.wang@....com>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: Re: [PATCH net] net: enetc: fix the netc-lib driver build dependency

On Wed, Jun 04, 2025 at 09:24:22AM +0200, Arnd Bergmann wrote:
> On Wed, Jun 4, 2025, at 04:44, Wei Fang wrote:
> >> Ok, so to summarize, you want nxp-netc-lib.ko to be separate from
> >> fsl-enetc-core.ko, because when you upstream the switch driver (also a
> >> consumer of ntmp.o), you want it to depend just on nxp-netc-lib.ko but
> >> not on the full fsl-enetc-core.ko.
> >> If the only reverse dependency of NXP_NETC_LIB, NXP_ENETC4, becomes m,
> >> then NXP_NETC_LIB also becomes m, but in reality, FSL_ENETC_CORE, via
> >> cbdr.o, still depends on symbols from NXP_NETC_LIB.
> >> 
> >> So you influence NXP_NETC_LIB to not become m when its only selecter is m,
> >> instead stay y.
> >> 
> >> Won't this need to change, and become even more complicated when
> >> NXP_NETC_LIB gains another selecter, the switch driver?
> >
> > The dependency needs to be updated as follows when switch driver is
> > added, to avoid the compilation errors.
> >
> > default y if FSL_ENETC_CORE=y && (NXP_ENETC4=m || NET_DSA_NETC_SWITCH=m)
> >
> >> 
> >> >  	help
> >> >  	  This module provides common functionalities for both ENETC and NETC
> >> >  	  Switch, such as NETC Table Management Protocol (NTMP) 2.0, common tc
> >> > --
> >> > 2.34.1
> >> >
> >> 
> >> What about this interpretation? cbdr.o uses symbols from NXP_NETC_LIB,
> >> so the Kconfig option controlling cbdr.o, aka FSL_ENETC_CORE, should
> >> select NXP_NETC_LIB. This solves the problem in a way which is more
> >> logical to me, and doesn't need to change when the switch is later added.
> >> 
> >
> > Yes, this is also a solution. I thought that LS1028A does not need the netc-lib
> > driver at all. Doing so will result in netc-lib being compiled on the LS1028A
> > platform, which may be unacceptable, so I did not do this. Since you think
> > this is better, I will apply this solution next. Thanks.
> 
> I think this version should work, and make logical sense:
> 
> --- a/drivers/net/ethernet/freescale/enetc/Kconfig
> +++ b/drivers/net/ethernet/freescale/enetc/Kconfig
> @@ -1,6 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  config FSL_ENETC_CORE
>         tristate
> +       select NXP_NETC_LIB if NXP_ENETC_NTMP
>         help
>           This module supports common functionality between the PF and VF
>           drivers for the NXP ENETC controller.
> @@ -22,6 +23,9 @@ config NXP_NETC_LIB
>           Switch, such as NETC Table Management Protocol (NTMP) 2.0, common tc
>           flower and debugfs interfaces and so on.
>  
> +config NXP_ENETC_NTMP
> +       bool
> +
>  config FSL_ENETC
>         tristate "ENETC PF driver"
>         depends on PCI_MSI
> @@ -45,7 +49,7 @@ config NXP_ENETC4
>         select FSL_ENETC_CORE
>         select FSL_ENETC_MDIO
>         select NXP_ENETC_PF_COMMON
> -       select NXP_NETC_LIB
> +       select NXP_ENETC_NTMP
>         select PHYLINK
>         select DIMLIB
>         help
> 
> FSL_ENETC selects the feature it actually wants, and FSL_ENETC_CORE
> enables the module based on the set of features that are enabled.
> The switch module can then equally enable bool symbol. Not sure
> what the best name would be for that symbol, that depends on what
> you expect to get added to NXP_NETC_LIB.
> 
>      Arnd

Thanks, this seems to be the best proposal thus far. IMO it is also easy
to maintain and it also fully satisfies the imposed requirements. I checked
that when FSL_ENETC_CORE goes to m, NXP_NETC_LIB also goes to m, and
when it remains y, the latter also remains y. Note, FSL_ENETC_CORE only
goes to m when all its selecters are m. More importantly, when
NXP_ENETC4=n, NXP_NETC_LIB is also n. The drivers seem to build in all
cases.

Will you send a patch with this proposal, or should Wei do it with a
Suggested-by?