Re: [PATCH 1/3] leds: triggers: add support for RGB triggers

[Jacek Anaszewski]

On 03/19/2016 08:11 PM, Heiner Kallweit wrote:
> Am 18.03.2016 um 14:10 schrieb Jacek Anaszewski:
> > On 03/17/2016 08:53 PM, Heiner Kallweit wrote:
> > > Am 17.03.2016 um 14:41 schrieb Jacek Anaszewski:
> > > > Hi Heiner,
> > > >
> > > > On 03/13/2016 06:14 PM, Heiner Kallweit wrote:
> > > > > Add basic support for RGB triggers. Triggers with flag LED_TRIG_CAP_RGB
> > > > > set are available to RGB LED devices only.
> > > > >
> > > > > Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> > > > > ---
> > > > >     drivers/leds/led-triggers.c | 15 ++++++++++++---
> > > > >     include/linux/leds.h        |  3 +++
> > > > >     2 files changed, 15 insertions(+), 3 deletions(-)
> > > > >
> > > > > diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> > > > > index 2181581..3ccf88b 100644
> > > > > --- a/drivers/leds/led-triggers.c
> > > > > +++ b/drivers/leds/led-triggers.c
> > > > > @@ -30,6 +30,13 @@ static LIST_HEAD(trigger_list);
> > > > >
> > > > >      /* Used by LED Class */
> > > > >
> > > > > +static inline bool led_trig_check_rgb(struct led_trigger *trig,
> > > > > +                      struct led_classdev *led_cdev)
> > > > > +{
> > > > > +    return !(trig->flags & LED_TRIG_CAP_RGB) ||
> > > > > +           led_cdev->flags & LED_DEV_CAP_RGB;
> > > > > +}
> > > >
> > > > Could you explain what is the purpose of this function?
> > > > What actually do we want to check here?
> > > Triggers using RGB functionality can't be used with non-RGB LED's.
> > > This check checks for such unsupported combinations:
> > > It returns false if the trigger uses RGB functionality but LED doesn't
> > > support the RGB extension.
> >
> > We need more meaningful name for it. Maybe led_trigger_is_supported() ?
> > And let's make it no-op for !CONFIG_LEDS_CLASS_RGB case.
> OK, led_trigger_is_supported() is better.
>
> Making the function a no-op in the non-RGB case would have some impact:
> We'd have to make sure that all public trigger functions are a de-facto no-op
> for RGB triggers (at least register / unregister). Means we would need
> something like this in each public trigger function:
>
> #if !IS_ENABLED(CONFIG_LEDS_CLASS_RGB)
> 	if (trig->flags & LED_TRIG_CAP_RGB))
> 		return;
> #endif
>
> I think this would add a lot of overhead and therefore IMHO it's better to
> not make the check function a no-op.

Wouldn't it suffice to make the no-op returning true?
Preventing RGB trigger registration for non-RGB LED class configuration
seems to be different thing, also to be considered.

> > > > >     ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
> > > > >             const char *buf, size_t count)
> > > > >     {
> > > > > @@ -52,12 +59,12 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
> > > > >         down_read(&triggers_list_lock);
> > > > >         list_for_each_entry(trig, &trigger_list, next_trig) {
> > > > >             if (sysfs_streq(buf, trig->name)) {
> > > > > +            if (!led_trig_check_rgb(trig, led_cdev))
> > > > > +                break;
> > >
> > > Check for the case that userspace wants to set a RGB trigger for a non-RGB LED via sysfs.
> > >
> > > > >                 down_write(&led_cdev->trigger_lock);
> > > > >                 led_trigger_set(led_cdev, trig);
> > > > >                 up_write(&led_cdev->trigger_lock);
> > > > > -
> > > > > -            up_read(&triggers_list_lock);
> > > > > -            goto unlock;
> > > > > +            break;
> >
> > This seems to be an unrelated cleanup. Please submit it separately.
> OK
>
> > > > >             }
> > > > >         }
> > > > >         up_read(&triggers_list_lock);
> > > > > @@ -84,6 +91,8 @@ ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr,
> > > > >             len += sprintf(buf+len, "none ");
> > > > >
> > > > >         list_for_each_entry(trig, &trigger_list, next_trig) {
> > > > > +        if (!led_trig_check_rgb(trig, led_cdev))
> > > > > +            continue;
> > >
> > > Omit RGB triggers when listing the available triggers for a non-RGB LED via sysfs.
> > >
> > > > >             if (led_cdev->trigger && !strcmp(led_cdev->trigger->name,
> > > > >                                 trig->name))
> > > > >                 len += sprintf(buf+len, "[%s] ", trig->name);
> > > > > diff --git a/include/linux/leds.h b/include/linux/leds.h
> > > > > index 58e22e6..07eb074 100644
> > > > > --- a/include/linux/leds.h
> > > > > +++ b/include/linux/leds.h
> > > > > @@ -248,6 +248,9 @@ enum led_brightness led_hsv_to_rgb(enum led_brightness hsv);
> > > > >     struct led_trigger {
> > > > >         /* Trigger Properties */
> > > > >         const char     *name;
> > > > > +    u8        flags;
> > > > > +#define LED_TRIG_CAP_RGB    BIT(0)
> > > > > +
> > > > >         void        (*activate)(struct led_classdev *led_cdev);
> > > > >         void        (*deactivate)(struct led_classdev *led_cdev);


--
Best regards,
Jacek Anaszewski