netdev - Re: [PATCH] net: freescale: select CONFIG_FIXED

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Date:   Sat, 9 May 2020 15:04:04 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Arnd Bergmann <arnd@...db.de>, Jakub Kicinski <kuba@...nel.org>
Cc:     "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 5/9/2020 2:48 PM, Arnd Bergmann wrote:
> 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.

select FIXED_PHY appears the correct choice here we could think about
providing stubs if that is deemed useful, but in general these drivers
do tend to have a functional dependency on the fixed PHY and MDIO bus
subsystems.

Acked-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian