linux-kernel - Re: [PATCH 1/3 v2] thermal: core: Add some new helper functions to free resources

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Date:   Fri, 11 Aug 2017 16:20:23 +0800
From:   Zhang Rui <rui.zhang@...el.com>
To:     wharms@....de, Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     edubezval@...il.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 1/3 v2] thermal: core: Add some new helper functions to
 free resources

On Fri, 2017-08-11 at 09:30 +0200, walter harms wrote:
> 
> Am 08.08.2017 16:39, schrieb Christophe JAILLET:
> > 
> > In order to easily free resources allocated by
> > 'thermal_zone_create_device_groups()' we need 2 new helper
> > functions.
> > 
> > The first one undoes 'thermal_zone_create_device_groups()'.
> > The 2nd one undoes 'create_trip_attrs()', which is a function
> > called by
> > 'thermal_zone_create_device_groups()'.
> > 
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> > ---
> > These functions will be used in patch 2/3 in order to simplify
> > 'thermal_release()'
> > I've tried to implement it as close a possible as the way the
> > resources have
> > been allocated.
> > However, in 'thermal_release()', the code is simplier without some
> > additionnal 'if'.
> > No sure if we should prefer consistancy with allocation or
> > simplicity of code.
> > ---
> >  drivers/thermal/thermal_core.h  |  1 +
> >  drivers/thermal/thermal_sysfs.c | 29 +++++++++++++++++++++++++++++
> >  2 files changed, 30 insertions(+)
> > 
> > diff --git a/drivers/thermal/thermal_core.h
> > b/drivers/thermal/thermal_core.h
> > index 2412b3759e16..27e3b1df7360 100644
> > --- a/drivers/thermal/thermal_core.h
> > +++ b/drivers/thermal/thermal_core.h
> > @@ -71,6 +71,7 @@ int thermal_build_list_of_policies(char *buf);
> >  
> >  /* sysfs I/F */
> >  int thermal_zone_create_device_groups(struct thermal_zone_device
> > *, int);
> > +void thermal_zone_destroy_device_groups(struct thermal_zone_device
> > *);
> >  void thermal_cooling_device_setup_sysfs(struct
> > thermal_cooling_device *);
> >  /* used only at binding time */
> >  ssize_t
> > diff --git a/drivers/thermal/thermal_sysfs.c
> > b/drivers/thermal/thermal_sysfs.c
> > index a694de907a26..eb95d64b9446 100644
> > --- a/drivers/thermal/thermal_sysfs.c
> > +++ b/drivers/thermal/thermal_sysfs.c
> > @@ -605,6 +605,24 @@ static int create_trip_attrs(struct
> > thermal_zone_device *tz, int mask)
> >  	return 0;
> >  }
> >  
> > +/**
> > + * destroy_trip_attrs() - create attributes for trip points
> > + * @tz:		the thermal zone device
> > + *
> > + * helper function to free resources alocated by
> > create_trip_attrs()
> > + */
> > +static void(struct thermal_zone_device *tz)
> > +{
> > +	if (!tz)
> > +		return;
> > +
> > +	kfree(tz->trip_type_attrs);
> > +	kfree(tz->trip_temp_attrs);
> > +	if (tz->ops->get_trip_hyst)
> > +		kfree(tz->trip_hyst_attrs);
> > +	kfree(tz->trips_attribute_group.attrs);
> > +}
> > +
> >  int thermal_zone_create_device_groups(struct thermal_zone_device
> > *tz,
> >  				      int mask)
> >  {
> > @@ -637,6 +655,17 @@ int thermal_zone_create_device_groups(struct
> > thermal_zone_device *tz,
> >  	return 0;
> >  }
> >  
> > +void thermal_zone_destroy_device_groups(struct thermal_zone_device
> > *tz)
> > +{
> > +	if (!tz)
> > +		return;
> > +
> > +	if (tz->trips)
> > +		destroy_trip_attrs(tz);
> why the check for tz->trips ?
> destroy_trip_attrs does not access tz->trips->
> 
tz->trips is an integer represents the number of trip points.

We add this check because there is not any trips attributes if we don't
have any trip points.
It is true that the code also works if we don't have this check as
destroy_trip_attrs() would be no-op when tz->trips equals 0.
But I won't say this check is wrong.

thanks,
rui
> re,
>  wh
> 
> > 
> > +
> > +	kfree(tz->device.groups);
> > +}
> > +
> >  /* sys I/F for cooling device */
> >  static ssize_t
> >  thermal_cooling_device_type_show(struct device *dev,