Re: [PATCH 4/4] leds: trigger: Add pattern initialization from Device Tree

From: Jacek Anaszewski
Date: Sat Dec 08 2018 - 13:44:47 EST

Hi Krzysztof,

Thank you for the patch set.

Applied 1/4 and 2/4.

I'll hold on merging 3/4 until we sort out the issues
I have with this one. Please refer to my comment below.

On 12/7/18 1:32 PM, Krzysztof Kozlowski wrote:
Allow initialization of pattern used in pattern trigger from Device Tree

This is especially useful for embedded systems where the pattern trigger
would be used to indicate the process of boot status in a nice,
user-friendly blinking way. This initialization pattern will be used
till user-space is brought up and sets its own pattern, indicating the
boot status is for example finished.

Signed-off-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
drivers/leds/trigger/ledtrig-pattern.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/drivers/leds/trigger/ledtrig-pattern.c b/drivers/leds/trigger/ledtrig-pattern.c
index 1870cf87afe1..96309d3bc43c 100644
--- a/drivers/leds/trigger/ledtrig-pattern.c
+++ b/drivers/leds/trigger/ledtrig-pattern.c
@@ -11,6 +11,7 @@
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/of.h>
#include <linux/slab.h>
#include <linux/timer.h>
@@ -331,6 +332,21 @@ static const struct attribute_group *pattern_trig_groups[] = {
+static void pattern_init(struct led_classdev *led_cdev)
+ struct device_node *np = dev_of_node(led_cdev->dev);
+ const char *pattern;
+ if (!np)
+ return;
+ if (!of_property_read_string(np, "linux,trigger-pattern", &pattern)) {
+ if (strlen(pattern))
+ pattern_trig_store_patterns(led_cdev, pattern,
+ strlen(pattern), false);
+ }
static int pattern_trig_activate(struct led_classdev *led_cdev)
struct pattern_trig_data *data;
@@ -354,6 +370,8 @@ static int pattern_trig_activate(struct led_classdev *led_cdev)
timer_setup(&data->timer, pattern_trig_timer_function, 0);
led_cdev->activated = true;
+ pattern_init(led_cdev);

It means that the pattern defined in DT would be applied
whenever the pattern trigger is set for a LED class device,
whereas it should happen only on LED class device initialization,
if linux,default-trigger is set to "pattern".

What we would need for making that work is a generic support for
parsing trigger specific initialization data in the

return 0;

Best regards,
Jacek Anaszewski