[PATCH 0/9] hwmon: Add and use helper hwmon_visible_0444

[Guenter Roeck]

On 10/9/24 22:44, Heiner Kallweit wrote:
> On 10.10.2024 00:19, Guenter Roeck wrote:
>> On 10/9/24 13:02, Heiner Kallweit wrote:
>>> Several drivers simply return 0444 in their is_visible callback.
>>> Add a helper in hwmon core for this use case to avoid code duplication.
>>>
>>> There are more drivers outside drivers/hwmon which would benefit
>>> from this helper as well.
>>>
>>> Heiner Kallweit (9):
>>>     hwmon: Add helper hwmon_visible_0444
>>>     hwmon: i5500_temp: Use new helper hwmon_visible_0444
>>>     hwmon: surface_fan: Use new helper hwmon_visible_0444
>>>     hwmon: sl28cpld: Use new helper hwmon_visible_0444
>>>     hwmon: gsc: Use new helper hwmon_visible_0444
>>>     hwmon: powerz: Use new helper hwmon_visible_0444
>>>     hwmon: raspberrypi: Use new helper hwmon_visible_0444
>>>     hwmon: intel-m10-bmc: Use new helper hwmon_visible_0444
>>>     hwmon: nzxt-kraken2: Use new helper hwmon_visible_0444
>>>
>>>    drivers/hwmon/gsc-hwmon.c           |  9 +--------
>>>    drivers/hwmon/hwmon.c               |  7 +++++++
>>>    drivers/hwmon/i5500_temp.c          |  8 +-------
>>>    drivers/hwmon/intel-m10-bmc-hwmon.c |  9 +--------
>>>    drivers/hwmon/nzxt-kraken2.c        |  9 +--------
>>>    drivers/hwmon/powerz.c              |  8 +-------
>>>    drivers/hwmon/raspberrypi-hwmon.c   |  8 +-------
>>>    drivers/hwmon/sl28cpld-hwmon.c      |  9 +--------
>>>    drivers/hwmon/surface_fan.c         | 10 +---------
>>>    include/linux/hwmon.h               |  2 ++
>>>    10 files changed, 17 insertions(+), 62 deletions(-)
>>>
>>
>> I really don't want to add such hwmon-specific but at the same time
>> generic helpers. If such a helper is made available in the core kernel,
>> I'll be happy to accept patches using it, but otherwise please refrain
>> from submitting such patch series.
>>
> What would you consider a suited place, drivers/base or fs/sysfs or lib or .. ?
> For enum hwmon_sensor_types we have to include linux/hwmon.h. None of these
> places has any hwmon code, and I would expect concerns if generic core code
> includes subsystem headers.
> 

"There are more drivers outside drivers/hwmon which would benefit
from this helper as well" very clearly suggests that the function
is not hwmon specific. Yet, obviously it is if it requires a hwmon
include file.

If this is hwmon specific, I'll want to see a different solution.
Instead of calling an exported function, hwmon drivers should set the
is_visible callback to a defined value, such as HWMON_VISIBLE_0444.
This could be an ERR_PTR() which is converted by the hwmon core.
This lets us add, for example, HWMON_VISIBLE_0644, and it avoids the
notion that the function could be called by non-hwmon drivers
(and the notion that it is a function in the first place). Instead
of calling the callback directly, the hwmon core would then have a
helper function which evaluates the pointer and either returns
a constant or calls the callback.

Guenter