linux-kernel - Re: [PATCH] iio: stm32: fix adc/trigger link error

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Message-ID: <6b5ff28a-859d-973c-2da5-60a8bf50c378@st.com>
Date:   Mon, 25 Sep 2017 11:54:06 +0200
From:   Fabrice Gasnier <fabrice.gasnier@...com>
To:     Jonathan Cameron <jic23@...nel.org>
CC:     Arnd Bergmann <arnd@...db.de>, Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Lee Jones <lee.jones@...aro.org>, <linux-iio@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: stm32: fix adc/trigger link error

On 09/10/2017 06:00 PM, Jonathan Cameron wrote:
> On Wed, 6 Sep 2017 18:16:33 +0200
> Fabrice Gasnier <fabrice.gasnier@...com> wrote:
> 
>> On 09/06/2017 02:56 PM, Arnd Bergmann wrote:
>>> The ADC driver can trigger on either the timer or the lptim
>>> trigger, but it only uses a Kconfig 'select' statement
>>> to ensure that the first of the two is present. When the lptim
>>> trigger is enabled as a loadable module, and the adc driver
>>> is built-in, we now get a link error:
>>>
>>> drivers/iio/adc/stm32-adc.o: In function `stm32_adc_get_trig_extsel':
>>> stm32-adc.c:(.text+0x4e0): undefined reference to `is_stm32_lptim_trigger'
>>>
>>> We could use a second 'select' statement and always have both
>>> trigger drivers enabled when the adc driver is, but it seems that
>>> the lptimer trigger was intentionally left optional, so it seems
>>> better to keep it that way.  
>> Hi Arnd,
>>
>> This is correct, not all stm32 have this hardware.
>>>
>>> This adds a hack to use 'IS_REACHABLE()' rather than 'IS_ENABLED()',
>>> which avoids the link error, but instead leads to the lptimer trigger
>>> not being used in the broken configuration. I've added a runtime
>>> warning for this case to help users figure out what they did wrong
>>> if this should ever be done by accident.
>>>
>>> Fixes: f0b638a7f6db ("iio: adc: stm32: add support for lptimer triggers")
>>> Signed-off-by: Arnd Bergmann <arnd@...db.de>  
>> Tested-by: Fabrice Gasnier <fabrice.gasnier@...com>
> 
> This may take me a few weeks to pick up.  I don't want to
> pull the mfd immutable branch in just to have this fix, so this will
> get sorted after rc1 is out.
> 
> As ever, poke me if it looks like I've forgotten about it.

Hi Jonathan,

Di you apply this one?

Thanks,
Best Regards,
Fabrice
> Sorry for the delay!
> 
> Jonathan
> 
>>
>> Many thanks for the fix,
>> Best Regards,
>> Fabrice
>>> ---
>>>  include/linux/iio/timer/stm32-lptim-trigger.h | 5 ++++-
>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/iio/timer/stm32-lptim-trigger.h b/include/linux/iio/timer/stm32-lptim-trigger.h
>>> index 34d59bfdce2d..464458d20b16 100644
>>> --- a/include/linux/iio/timer/stm32-lptim-trigger.h
>>> +++ b/include/linux/iio/timer/stm32-lptim-trigger.h
>>> @@ -16,11 +16,14 @@
>>>  #define LPTIM2_OUT	"lptim2_out"
>>>  #define LPTIM3_OUT	"lptim3_out"
>>>  
>>> -#if IS_ENABLED(CONFIG_IIO_STM32_LPTIMER_TRIGGER)
>>> +#if IS_REACHABLE(CONFIG_IIO_STM32_LPTIMER_TRIGGER)
>>>  bool is_stm32_lptim_trigger(struct iio_trigger *trig);
>>>  #else
>>>  static inline bool is_stm32_lptim_trigger(struct iio_trigger *trig)
>>>  {
>>> +#if IS_ENABLED(CONFIG_IIO_STM32_LPTIMER_TRIGGER)
>>> +	pr_warn_once("stm32 lptim_trigger not linked in\n");
>>> +#endif
>>>  	return false;
>>>  }
>>>  #endif
>>>   
>> --
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>