diff mbox series

[v1,1/6] thermal: trip: Simplify computing trip indices

Message ID 3256881.aeNJFYEL58@kreacher
State New
Headers
Series thermal: core: Pass trip pointers to governor .throttle() callbacks |

Commit Message

Rafael J. Wysocki Oct. 6, 2023, 5:40 p.m. UTC 
  From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

A trip index can be computed right away as a difference between the
value of a trip pointer pointing to the given trip object and the
start of the trips[] table in the thermal zone containing the trip, so
change thermal_zone_trip_id() accordingly.

No intentional functional impact (except for some speedup).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/thermal/thermal_trip.c |   13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

Comments

Daniel Lezcano Oct. 12, 2023, 2:27 p.m. UTC | #1 
On 06/10/2023 19:40, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> A trip index can be computed right away as a difference between the
> value of a trip pointer pointing to the given trip object and the
> start of the trips[] table in the thermal zone containing the trip, so
> change thermal_zone_trip_id() accordingly.
> 
> No intentional functional impact (except for some speedup).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>   drivers/thermal/thermal_trip.c |   13 +++++--------
>   1 file changed, 5 insertions(+), 8 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_trip.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_trip.c
> +++ linux-pm/drivers/thermal/thermal_trip.c
> @@ -175,14 +175,11 @@ int thermal_zone_set_trip(struct thermal
>   int thermal_zone_trip_id(struct thermal_zone_device *tz,
>   			 const struct thermal_trip *trip)
>   {
> -	int i;
> -
>   	lockdep_assert_held(&tz->lock);
>   
> -	for (i = 0; i < tz->num_trips; i++) {
> -		if (&tz->trips[i] == trip)
> -			return i;
> -	}
> -
> -	return -ENODATA;
> +	/*
> +	 * Assume the trip to be located within the bounds of the thermal
> +	 * zone's trips[] table.
> +	 */
> +	return trip - tz->trips;

Shouldn't be divided by sizeof(*trip) ?

>   }
> 
> 
>
Rafael J. Wysocki Oct. 12, 2023, 4:21 p.m. UTC | #2 
On Thu, Oct 12, 2023 at 4:27 PM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> On 06/10/2023 19:40, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > A trip index can be computed right away as a difference between the
> > value of a trip pointer pointing to the given trip object and the
> > start of the trips[] table in the thermal zone containing the trip, so
> > change thermal_zone_trip_id() accordingly.
> >
> > No intentional functional impact (except for some speedup).
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> >   drivers/thermal/thermal_trip.c |   13 +++++--------
> >   1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > Index: linux-pm/drivers/thermal/thermal_trip.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_trip.c
> > +++ linux-pm/drivers/thermal/thermal_trip.c
> > @@ -175,14 +175,11 @@ int thermal_zone_set_trip(struct thermal
> >   int thermal_zone_trip_id(struct thermal_zone_device *tz,
> >                        const struct thermal_trip *trip)
> >   {
> > -     int i;
> > -
> >       lockdep_assert_held(&tz->lock);
> >
> > -     for (i = 0; i < tz->num_trips; i++) {
> > -             if (&tz->trips[i] == trip)
> > -                     return i;
> > -     }
> > -
> > -     return -ENODATA;
> > +     /*
> > +      * Assume the trip to be located within the bounds of the thermal
> > +      * zone's trips[] table.
> > +      */
> > +     return trip - tz->trips;
>
> Shouldn't be divided by sizeof(*trip) ?

No, it's in sizeof(*trip) units already.
Lukasz Luba Oct. 20, 2023, 4:58 p.m. UTC | #3 
On 10/6/23 18:40, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> A trip index can be computed right away as a difference between the
> value of a trip pointer pointing to the given trip object and the
> start of the trips[] table in the thermal zone containing the trip, so
> change thermal_zone_trip_id() accordingly.
> 
> No intentional functional impact (except for some speedup).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>   drivers/thermal/thermal_trip.c |   13 +++++--------
>   1 file changed, 5 insertions(+), 8 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_trip.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_trip.c
> +++ linux-pm/drivers/thermal/thermal_trip.c
> @@ -175,14 +175,11 @@ int thermal_zone_set_trip(struct thermal
>   int thermal_zone_trip_id(struct thermal_zone_device *tz,
>   			 const struct thermal_trip *trip)
>   {
> -	int i;
> -
>   	lockdep_assert_held(&tz->lock);
>   
> -	for (i = 0; i < tz->num_trips; i++) {
> -		if (&tz->trips[i] == trip)
> -			return i;
> -	}
> -
> -	return -ENODATA;
> +	/*
> +	 * Assume the trip to be located within the bounds of the thermal
> +	 * zone's trips[] table.
> +	 */
> +	return trip - tz->trips;
>   }
> 
> 
> 

I agree wit hthe comment, we should be safe here, since we control that
array.

I could be a bit picky about this 'int' return in that function on
64bit kernels, were we have also ptrdiff_t set to long IIRC. But this
particular usage should be handled properly in all our cases, so:

Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Rafael J. Wysocki Oct. 20, 2023, 5:04 p.m. UTC | #4 
On Fri, Oct 20, 2023 at 6:58 PM Lukasz Luba <lukasz.luba@arm.com> wrote:
>
>
>
> On 10/6/23 18:40, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > A trip index can be computed right away as a difference between the
> > value of a trip pointer pointing to the given trip object and the
> > start of the trips[] table in the thermal zone containing the trip, so
> > change thermal_zone_trip_id() accordingly.
> >
> > No intentional functional impact (except for some speedup).
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> >   drivers/thermal/thermal_trip.c |   13 +++++--------
> >   1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > Index: linux-pm/drivers/thermal/thermal_trip.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_trip.c
> > +++ linux-pm/drivers/thermal/thermal_trip.c
> > @@ -175,14 +175,11 @@ int thermal_zone_set_trip(struct thermal
> >   int thermal_zone_trip_id(struct thermal_zone_device *tz,
> >                        const struct thermal_trip *trip)
> >   {
> > -     int i;
> > -
> >       lockdep_assert_held(&tz->lock);
> >
> > -     for (i = 0; i < tz->num_trips; i++) {
> > -             if (&tz->trips[i] == trip)
> > -                     return i;
> > -     }
> > -
> > -     return -ENODATA;
> > +     /*
> > +      * Assume the trip to be located within the bounds of the thermal
> > +      * zone's trips[] table.
> > +      */
> > +     return trip - tz->trips;
> >   }
> >
> >
> >
>
> I agree wit hthe comment, we should be safe here, since we control that
> array.
>
> I could be a bit picky about this 'int' return in that function on
> 64bit kernels, were we have also ptrdiff_t set to long IIRC. But this
> particular usage should be handled properly in all our cases, so:
>
> Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
> Tested-by: Lukasz Luba <lukasz.luba@arm.com>

Thanks!
diff mbox series

Patch

Index: linux-pm/drivers/thermal/thermal_trip.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_trip.c
+++ linux-pm/drivers/thermal/thermal_trip.c
@@ -175,14 +175,11 @@  int thermal_zone_set_trip(struct thermal
 int thermal_zone_trip_id(struct thermal_zone_device *tz,
 			 const struct thermal_trip *trip)
 {
-	int i;
-
 	lockdep_assert_held(&tz->lock);
 
-	for (i = 0; i < tz->num_trips; i++) {
-		if (&tz->trips[i] == trip)
-			return i;
-	}
-
-	return -ENODATA;
+	/*
+	 * Assume the trip to be located within the bounds of the thermal
+	 * zone's trips[] table.
+	 */
+	return trip - tz->trips;
 }