Re: [PATCH] thermal/sysfs: Always enable hysteresis write support

[Manaf Meethalavalappu Pallikunhi]

Resending to reflect to format

Hi Rafael,

On 1/9/2024 7:12 PM, Rafael J. Wysocki wrote:
> On Sat, Jan 6, 2024 at 8:16 PM Manaf Meethalavalappu Pallikunhi
> <quic_manafm@xxxxxxxxxxx> wrote:
> > The commit 2e38a2a981b2("thermal/core: Add a generic
> > thermal_zone_set_trip() function") adds the support to update
> > trip hysteresis even if set_trip_hyst() operation is not defined.
> > But during hysteresis attribute creation, if this operation is
> > defined then only it enables hysteresis write access. It leads
> > to a case where hysteresis sysfs will be read only for a thermal
> > zone when its set_trip_hyst() operation is not defined.
I think it is regression after recent re-work.  If  a sensor  is 
registered witht thermal framework via thermal_of,  sensor driver 
doesn't need to  know the trip configuration and nothing to do with 
set_trip_hyst() in driver. Without this change, if  a sensor needs to be 
monitored from userspace(trip/hysteresis), it is enforcing sensor driver 
to add  dummy set_trip_hyst() operation. Correct me otherwise.
> Which is by design.
>
> For some thermal zone types (eg. acpi), updating trip hysteresis via
> sysfs might lead to incorrect behavior.

To address this, is it okay to guard hysteresis write permission under 
CONFIG_THERMAL_WRITABLE_TRIPS flag ?

Thanks,

Manaf