[PATCH v7 1/3] backlight: Add IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)

[Daniel Thompson]

On 02/10/17 06:58, Daniel Thompson wrote:
> On 01/10/17 18:26, Meghana Madhyastha wrote:
>> Add IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) as part of the
>> if directive for the function declaration of
>> of_find_backlight_by_node in order to avoid module dependency
>> errors.
> 
> Module dependency errors? Does you mean mean use of undefined symbols?

Sorry, drafting error! Could you pretend I wrote "Do you mean use of..." 
instead of the nonsense above!

> 
> 
>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha at gmail.com>
>> ---
>> Changes in v7:
>> -This patch did not exist in v6.
> 
> So I'm coming to this patchset cold but can you explain *why* something 
> wants to call of_find_backlight_by_node() when there is no backlight 
> support enabled. Why isn't the code that called is conditional on 
> BACKLIGHT_CLASS_DEVICE?
> 
> The undefined symbol issue is a pain but to be honest I'd rather solve 
> the use of undefined symbols by avoiding declaring them; this making 
> them into compile errors rather than link errors.
> 
> 
>>   include/linux/backlight.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
>> index 5f2fd61..a52ce82 100644
>> --- a/include/linux/backlight.h
>> +++ b/include/linux/backlight.h
>> @@ -162,7 +162,7 @@ struct generic_bl_info {
>>       void (*kick_battery)(void);
>>   };
>> -#ifdef CONFIG_OF
>> +#if defined CONFIG_OF && IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
> 
> The above comments are more important but why does this mix defined and 
> IS_ENABLED? Couldn't they both use defined (and preferably with the 
> optional brackets around the CONFIG_ symbol).
> 
> 
> Daniel.