linux-kernel - Re: [PATCH 8/9] can: calc_bittiming: add PWM calculation

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Message-ID: <b4a32eff-1ca8-4707-b48b-b3b4dd04c25f@kernel.org>
Date: Tue, 14 Oct 2025 11:05:13 +0900
From: Vincent Mailhol <mailhol@...nel.org>
To: kernel test robot <lkp@...el.com>, Marc Kleine-Budde
 <mkl@...gutronix.de>, Oliver Hartkopp <socketcan@...tkopp.net>
Cc: oe-kbuild-all@...ts.linux.dev,
 Stéphane Grosjean <stephane.grosjean@...-networks.com>,
 Robert Nawrath <mbro1689@...il.com>, Minh Le <minh.le.aj@...esas.com>,
 Duy Nguyen <duy.nguyen.rh@...esas.com>, linux-can@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/9] can: calc_bittiming: add PWM calculation

On 14/10/2025 at 06:21, kernel test robot wrote:
> Hi Vincent,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on cb6649f6217c0331b885cf787f1d175963e2a1d2]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Vincent-Mailhol/can-dev-can_dev_dropped_skb-drop-CAN-FD-skbs-if-FD-is-off/20251013-191232
> base:   cb6649f6217c0331b885cf787f1d175963e2a1d2
> patch link:    https://lore.kernel.org/r/20251013-canxl-netlink-v1-8-f422b7e2729f%40kernel.org
> patch subject: [PATCH 8/9] can: calc_bittiming: add PWM calculation
> config: riscv-randconfig-001-20251014 (https://download.01.org/0day-ci/archive/20251014/202510140553.qo3f0I9s-lkp@intel.com/config)
> compiler: riscv64-linux-gcc (GCC) 10.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251014/202510140553.qo3f0I9s-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/202510140553.qo3f0I9s-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from include/linux/can/dev.h:18,
>                     from net/can/raw.c:53:
>    include/linux/can/bittiming.h: In function 'can_calc_pwm':
>>> include/linux/can/bittiming.h:204:1: warning: no return statement in function returning non-void [-Wreturn-type]
>      204 | }
>          | ^
> 
> Kconfig warnings: (for reference only)
>    WARNING: unmet direct dependencies detected for ARCH_HAS_ELF_CORE_EFLAGS
>    Depends on [n]: BINFMT_ELF [=y] && ELF_CORE [=n]
>    Selected by [y]:
>    - RISCV [=y]
> 
> 
> vim +204 include/linux/can/bittiming.h
> 
>    200	
>    201	static inline int
>    202	can_calc_pwm(struct net_device *dev, struct netlink_ext_ack *extack)
>    203	{
>  > 204	}
>    205	#endif /* CONFIG_CAN_CALC_BITTIMING */
>    206	

I see, this only occurs if CONFIG_CAN_CALC_BITTIMING is not set.

What is surprising enough is that can_calc_tdco() has the exact same
issue but we never received a report.

I will first send a separate fix for can_calc_tdco() targeting
net/main and send the v2 for this series once the can_calc_tdco() fix
reaches net-next/main.


Yours sincerely,
Vincent Mailhol