linux-kernel - Re: [PATCH v1 1/1] mux: consumer: Add dummy functions for !CONFIG

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Date:   Sat, 8 Jul 2017 16:04:30 -0700
From:   "Kuppuswamy, Sathyanarayanan" <sathyaosid@...il.com>
To:     Peter Rosin <peda@...ntia.se>,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] mux: consumer: Add dummy functions for
 !CONFIG_MULTIPLEXER case

Hi Peter,

On 7/8/2017 1:55 PM, Peter Rosin wrote:
> On 2017-07-07 23:41, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>
>> Add dummy functions to avoid compile time issues when CONFIG_MULTIPLEXER
>> is not enabled.
> Hi!
>
> Consumers should "select MULTIPLEXER",
  If their driver can't work without mux_* calls then  you can make it 
compulsory. But its not always true.
>   so this does not make sense.
> Or do you have a driver that has an optional mux consumer?
I came across this case when I was working on Intel USB MUX driver. I 
think you know the history behind it. Although I am not planning to 
merge that driver now, but I think the use case is still valid.
>
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>> ---
>>   include/linux/mux/consumer.h | 38 ++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 38 insertions(+)
>>
>> diff --git a/include/linux/mux/consumer.h b/include/linux/mux/consumer.h
>> index 5577e1b..744a5b8 100644
>> --- a/include/linux/mux/consumer.h
>> +++ b/include/linux/mux/consumer.h
>> @@ -16,6 +16,7 @@
>>   struct device;
>>   struct mux_control;
>>   
>> +#ifdef CONFIG_MULTIPLEXER
>>   unsigned int mux_control_states(struct mux_control *mux);
>>   int __must_check mux_control_select(struct mux_control *mux,
>>   				    unsigned int state);
>> @@ -29,4 +30,41 @@ void mux_control_put(struct mux_control *mux);
>>   struct mux_control *devm_mux_control_get(struct device *dev,
>>   					 const char *mux_name);
>>   
>> +#else
>> +unsigned int mux_control_states(struct mux_control *mux)
> static inline
>
> Cheers,
> peda
>
>> +{
>> +	return -ENODEV;
>> +}
>> +
>> +int __must_check mux_control_select(struct mux_control *mux,
>> +				    unsigned int state)
>> +{
>> +	return -ENODEV;
>> +}
>> +
>> +int __must_check mux_control_try_select(struct mux_control *mux,
>> +					unsigned int state)
>> +{
>> +	return -ENODEV;
>> +}
>> +
>> +int mux_control_deselect(struct mux_control *mux)
>> +{
>> +	return -ENODEV;
>> +}
>> +
>> +struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
>> +{
>> +	return ERR_PTR(-ENODEV);
>> +}
>> +
>> +void mux_control_put(struct mux_control *mux) {}
>> +
>> +struct mux_control *devm_mux_control_get(struct device *dev,
>> +					 const char *mux_name)
>> +{
>> +	return ERR_PTR(-ENODEV);
>> +}
>> +#endif
>> +
>>   #endif /* _LINUX_MUX_CONSUMER_H */
>>