Subject: Re: [PATCH] hwmon/sensors: fix SENSORS_LM75 dependencies

From: Eduardo Valentin <[email-masked]>
Date: Tue, 7 Jan 2014 07:35:07 -0400

On 06-01-2014 22:26, Guenter Roeck wrote:
> On 01/06/2014 05:09 PM, Randy Dunlap wrote:
>> On 01/06/14 12:32, Guenter Roeck wrote:
>>> On Mon, Jan 06, 2014 at 11:51:36AM -0800, Randy Dunlap wrote:
>>>> On 01/06/14 01:40, Stephen Rothwell wrote:
>>>>> Hi all,
>>>>>
>>>>> This tree fails (more than usual) the powerpc allyesconfig build.
>>>>>
>>>>> Changes since 20131224:
>>>>>
>>>>
>>>>
>>>> on i386:
>>>>
>>>> drivers/built-in.o: In function `lm75_remove':
>>>> lm75.c:(.text+0x12bd8c): undefined reference to
>>>> `thermal_zone_of_sensor_unregister'
>>>> drivers/built-in.o: In function `lm75_probe':
>>>> lm75.c:(.text+0x12c123): undefined reference to
>>>> `thermal_zone_of_sensor_register'
>>>>
>>>
>>> AFAICS that is a dependency problem in thermal code.
>>> CONFIG_THERMAL=m defines the symbols, but CONFIG_SENSORS_LM75=y.
>>
>> CONFIG_THERMAL_OF defines the symbols.
>>
>> It looks to me like drivers/hwmon/Kconfig SENSORS_LM75 entry needs a
>>     depends on THERMAL_OF
>> line, but that won't fix this build error.
>> The problem (once again, not the first time that I have seen this one)
>> is that
>> we have a tristate =m that depends on a bool =y.
>>
>> Hm, I bet a "depends on THERMAL" for SENSORS_LM75 will fix this.
>> [test]
>> Yes, that restricts (limits) SENSORS_LM75 to n/m; y is not possible.
>>
>> Patch for your consideration is below.
>>
>>>
>>> Up to the thermal folks to fix; if the code ends up in mainline we'll
>>> have to
>>> revert the patch introducing the calls to the lm75 driver (and the
>>> tmp102 driver
>>> which has the same issue).
>>>
>>> Another oddity is the help text to THERMAL_OF, which states that it
>>> supports
>>> reading and parsing thermal data definitions out of dt but fails to
>>> mention
>>> that it also provides the above API functions.
>>
>> ---
>> From: Randy Dunlap <[email-masked]>
>>
>> Fix SENSORS_LM75 dependencies to eliminate build errors:
>>
>> drivers/built-in.o: In function `lm75_remove':
>> lm75.c:(.text+0x12bd8c): undefined reference to
>> `thermal_zone_of_sensor_unregister'
>> drivers/built-in.o: In function `lm75_probe':
>> lm75.c:(.text+0x12c123): undefined reference to
>> `thermal_zone_of_sensor_register'
>>
>> Add depends on THERMAL_OF since that is what provides the
>> register/unregister functions above.
>>
>> Add depends on THERMAL since THERMAL is a tristate (while THERMAL_OF
>> is a bool) and SENSORS_LM75 (tristate) needs to be limited to modular
>> builds when THERMAL=m.
>>
>> Signed-off-by: Randy Dunlap <[email-masked]>
>> ---
>>   drivers/hwmon/Kconfig |    2 ++
>>   1 file changed, 2 insertions(+)
>>
>> --- linux-next-20140106.orig/drivers/hwmon/Kconfig
>> +++ linux-next-20140106/drivers/hwmon/Kconfig
>> @@ -650,6 +650,8 @@ config SENSORS_LM73
>>   config SENSORS_LM75
>>       tristate "National Semiconductor LM75 and compatibles"
>>       depends on I2C
>> +    depends on THERMAL
>> +    depends on THERMAL_OF
>>       help
>>         If you say yes here you get support for one common type of
>>         temperature sensor chip, with models including:
>>
>>
> NACK. The driver does not and must not depend on THERMAL. This needs to
> be addressed
> in the thermal code, for example with dummy declarations if THERMAL=m but
> SENSORS_LM75=y. The functions are already declared as dummies if
> THERMAL_OF=n.

What do you mean by that? The code of an API provider needs to keep
track of all its users?

> Guenter

-- 
You have got to be excited about what you are doing. (L. Lamport)

Eduardo Valentin