linux-kernel - Re: [PATCH v3] media: rc: pwm-ir-tx: Switch to atomic PWM API

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Date:   Wed, 27 Oct 2021 08:32:04 +0100
From:   Sean Young <sean@...s.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     kernel test robot <lkp@...el.com>,
        Maíra Canal <maira.canal@....br>,
        mchehab@...nel.org, thierry.reding@...il.com, lee.jones@...aro.org,
        llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH v3] media: rc: pwm-ir-tx: Switch to atomic PWM API

On Wed, Oct 27, 2021 at 08:15:52AM +0200, Uwe Kleine-König wrote:
> On Wed, Oct 27, 2021 at 02:07:19PM +0800, kernel test robot wrote:
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@...el.com>
> > 
> > All errors (new ones prefixed by >>, old ones prefixed by <<):
> > 
> > >> ERROR: modpost: "__udivdi3" [drivers/media/rc/pwm-ir-tx.ko] undefined!
> 
> This comes from the line:
> 
> 	state.duty_cycle = DIV_ROUND_CLOSEST(pwm_ir->duty_cycle * state.period, 100);
> 
> where DIV_ROUND_CLOSEST expands to a normal division but state.period is
> a u64. So this should use DIV64_U64_ROUND_CLOSEST I guess.

DIV64_U64_ROUND_CLOSEST is for dividing a u64 with a u64. We're dividing
by 100 here so this is not necessary.

It should use DIV_ROUND_CLOSEST_ULL, however it might be nicer to use:

	pwm_set_relative_duty_cycle(&state, pwm_ir->duty_cycle, 100);

Thanks

Sean