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

From: Jacek Anaszewski
Date: Mon Mar 21 2016 - 11:36:14 EST


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