linux-kernel - Re: [PATCH] net: freescale: select CONFIG_FIXED

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Message-ID: <CAK8P3a0figw8FHGp2KqW6XdfbWLu_ZXp3hyuPVoPwpum6XeJ_Q@mail.gmail.com>
Date:   Sat, 9 May 2020 23:48:55 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Madalin Bucur <madalin.bucur@....com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Timur Tabi <timur@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH] net: freescale: select CONFIG_FIXED_PHY where needed

On Sat, May 9, 2020 at 10:24 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Sat,  9 May 2020 14:04:52 +0200 Arnd Bergmann wrote:
> > I ran into a randconfig build failure with CONFIG_FIXED_PHY=m
> > and CONFIG_GIANFAR=y:
> >
> > x86_64-linux-ld: drivers/net/ethernet/freescale/gianfar.o:(.rodata+0x418): undefined reference to `fixed_phy_change_carrier'
> >
> > It seems the same thing can happen with dpaa and ucc_geth, so change
> > all three to do an explicit 'select FIXED_PHY'.
> >
> > The fixed-phy driver actually has an alternative stub function that
> > theoretically allows building network drivers when fixed-phy is
> > disabled, but I don't see how that would help here, as the drivers
> > presumably would not work then.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> > +     select FIXED_PHY
>
> I think FIXED_PHY needs to be optional, depends on what the board has
> connected to the MAC it may not be needed, right PHY folks? We probably
> need the
>
>     depends on FIXED_PHY || !FIXED_PHY

Unfortunately that does not work because it causes a circular dependency:

drivers/net/phy/Kconfig:415:error: recursive dependency detected!
drivers/net/phy/Kconfig:415: symbol FIXED_PHY depends on PHYLIB
drivers/net/phy/Kconfig:250: symbol PHYLIB is selected by FSL_PQ_MDIO
drivers/net/ethernet/freescale/Kconfig:60: symbol FSL_PQ_MDIO is
selected by UCC_GETH
drivers/net/ethernet/freescale/Kconfig:75: symbol UCC_GETH depends on FIXED_PHY

I now checked what other drivers use the fixed-phy interface, and found
that all others do select FIXED_PHY except for these three, and they
are also the only ones using fixed_phy_change_carrier().

The fixed-phy driver is fairly small, so it probably won't harm too much
to use the select, but maybe I missed another option.

        Arnd