linux-kernel - Re: [PATCH v4 2/7] mux: Add helper functions for getting optional and selected mux-state

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Message-ID: <9e172c95-25bb-4608-932c-e761b1b1802d@kernel.org>
Date: Thu, 8 Jan 2026 08:45:08 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Josua Mayer <josua@...id-run.com>, Ulf Hansson <ulf.hansson@...aro.org>,
 Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Magnus Damm <magnus.damm@...il.com>,
 Wolfram Sang <wsa-dev@...g-engineering.com>,
 Marc Kleine-Budde <mkl@...gutronix.de>, Vincent Mailhol
 <mailhol@...nel.org>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Peter Rosin <peda@...ntia.se>,
 Aaro Koskinen <aaro.koskinen@....fi>, Andreas Kemnade
 <andreas@...nade.info>, Kevin Hilman <khilman@...libre.com>,
 Roger Quadros <rogerq@...nel.org>, Tony Lindgren <tony@...mide.com>,
 Vignesh R <vigneshr@...com>, Janusz Krzysztofik <jmkrzyszt@...il.com>,
 Andi Shyti <andi.shyti@...nel.org>,
 Neil Armstrong <neil.armstrong@...aro.org>, kernel test robot <lkp@...el.com>
Cc: "oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>,
 Mikhail Anikin <mikhail.anikin@...id-run.com>,
 Yazan Shhady <yazan.shhady@...id-run.com>, Jon Nettleton
 <jon@...id-run.com>, "linux-mmc@...r.kernel.org"
 <linux-mmc@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
 "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>
Subject: Re: [PATCH v4 2/7] mux: Add helper functions for getting optional and
 selected mux-state

On 08/01/2026 08:42, Josua Mayer wrote:
> On Wednesday, 31 December 2025 21:18:51 IST kernel test robot wrote:
>> Hi Josua,
>>
>> kernel test robot noticed the following build errors:
>>
>> [auto build test ERROR on 8f0b4cce4481fb22653697cced8d0d04027cb1e8]
>>
>> url:   
>> https://github.com/intel-lab-lkp/linux/commits/Josua-Mayer/phy-can-transcei
>> ver-rename-temporary-helper-function-to-avoid-conflict/20251229-223153 base:
>>   8f0b4cce4481fb22653697cced8d0d04027cb1e8
>> patch link:   
>> https://lore.kernel.org/r/20251229-rz-sdio-mux-v4-2-a023e55758fe%40solid-ru
>> n.com patch subject: [PATCH v4 2/7] mux: Add helper functions for getting
>> optional and selected mux-state config: parisc-randconfig-002-20260101
>> (https://download.01.org/0day-ci/archive/20260101/202601010305.tpY47HE4-lkp
>> @intel.com/config) compiler: hppa-linux-gcc (GCC) 10.5.0
>> reproduce (this is a W=1 build):
>> (https://download.01.org/0day-ci/archive/20260101/202601010305.tpY47HE4-lkp
>> @intel.com/reproduce)
>>
>> If you fix the issue in a separate patch/commit (i.e. not just a new version
>> of the same patch/commit), kindly add following tags
>>
>> | Reported-by: kernel test robot <lkp@...el.com>
>> | Closes:
>> | https://lore.kernel.org/oe-kbuild-all/202601010305.tpY47HE4-lkp@intel.com
>> | /
>> All error/warnings (new ones prefixed by >>):
>>
>>    In file included from drivers/mux/core.c:19:
>>
>>    include/linux/mux/consumer.h: In function 'mux_control_put':
>>>> include/linux/mux/consumer.h:138:9: warning: 'return' with a value, in
>>>> function returning void [-Wreturn-type]
>>      138 |  return -EOPNOTSUPP;
>>
>>          |         ^
>>
> To be fixed in next version
> 
>>    include/linux/mux/consumer.h:136:20: note: declared here
>>      136 | static inline void mux_control_put(struct mux_control *mux)
>>
>>          |                    ^~~~~~~~~~~~~~~
>>
>>    drivers/mux/core.c: At top level:
>>>> drivers/mux/core.c:302:14: error: redefinition of 'mux_control_states'
>>
>>      302 | unsigned int mux_control_states(struct mux_control *mux)
>>
>>          |              ^~~~~~~~~~~~~~~~~~
>>
>>    In file included from drivers/mux/core.c:19:
>>    include/linux/mux/consumer.h:70:28: note: previous definition of
>> 'mux_control_states' was here 70 | static inline unsigned int
>> mux_control_states(struct mux_control *mux)
>>          |                            ^~~~~~~~~~~~~~~~~~
> 
> I don't understand how this is possible.
> In the header file line 136 the inline declaration for mux_control_states is 
> gated by ifdef CONFIG_MULTIPLEXER else case.
> 
> The build of mux/core.c itself is gated in Makefile by CONFIG_MULTIPLEXER.
> 
> So mux/core.c is not being built when CONFIG_MULTIPLEXER is not set.
> If it is set, we hit in the header file the non-inline declaration near start
> of the file.


You have all the tools in this email to actually reproduce it. Did you try?

Best regards,
Krzysztof