This series makes it possible for the LED core to manage the power supply
of a LED. It uses the regulator API to disable/enable the power if when the
LED is turned on/off.
This is especially useful in situations where the LED driver/controller is
not supplying the power.
While at it, throw in a fix for led_set_brightness_sync() so that it can
work with drivers that don't provide brightness_set_blocking()
changes in v3:
- reword device-tree description
- reword commit log
- remove regulator updates from functions used in atomic context. If the
regulator must be updated, it is defered to a workqueue.
- Fix led_set_brightness_sync() to work with the non-blocking function
__led_set_brightness()
changes in v2:
- use devm_regulator_get_optional() to avoid using the dummy regulator and
do some unnecessary work
Jean-Jacques Hiblot (3):
dt-bindings: leds: document the "power-supply" property
leds: Add control of the voltage/current regulator to the LED core
leds: Make led_set_brightness_sync() also use __led_set_brightness()
.../devicetree/bindings/leds/common.txt | 4 ++
drivers/leds/led-class.c | 15 ++++++
drivers/leds/led-core.c | 53 +++++++++++++++++--
drivers/leds/leds.h | 1 +
include/linux/leds.h | 4 ++
5 files changed, 73 insertions(+), 4 deletions(-)
--
2.17.1
There are some LED drivers that do not implement brightness_set_blocking(),
for those drivers led_set_brightness_sync() cannot work.
Fixing it by calling first __led_set_brightness() and falling back to
__led_set_brightness_blocking() if it failed.
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
---
drivers/leds/led-core.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index dab32cf778f2..4a0506081c0e 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -320,15 +320,19 @@ int led_set_brightness_sync(struct led_classdev *led_cdev,
if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
return -EBUSY;
- led_cdev->brightness = min(value, led_cdev->max_brightness);
+ value = min(value, led_cdev->max_brightness);
if (led_cdev->flags & LED_SUSPENDED)
return 0;
- ret = __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
+ ret = __led_set_brightness(led_cdev, value);
+ if (ret == -ENOTSUPP)
+ ret = __led_set_brightness_blocking(led_cdev, value);
if (ret)
return ret;
+ led_cdev->brightness = value;
+
return __led_handle_regulator(led_cdev, led_cdev->brightness);
}
EXPORT_SYMBOL_GPL(led_set_brightness_sync);
--
2.17.1
Sometimes LEDs are powered by an external voltage/current regulator. Let
the LED core know about it. This allows the LED core to turn on or off
managed power supplies.
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
Reviewed-by: Dan Murphy <[email protected]>
---
drivers/leds/led-class.c | 15 +++++++++++++
drivers/leds/led-core.c | 47 +++++++++++++++++++++++++++++++++++++---
drivers/leds/leds.h | 1 +
include/linux/leds.h | 4 ++++
4 files changed, 64 insertions(+), 3 deletions(-)
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 4793e77808e2..cadd43c30d50 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -253,6 +253,7 @@ int of_led_classdev_register(struct device *parent, struct device_node *np,
{
char name[LED_MAX_NAME_SIZE];
int ret;
+ struct regulator *regulator;
ret = led_classdev_next_name(led_cdev->name, name, sizeof(name));
if (ret < 0)
@@ -272,6 +273,20 @@ int of_led_classdev_register(struct device *parent, struct device_node *np,
dev_warn(parent, "Led %s renamed to %s due to name collision",
led_cdev->name, dev_name(led_cdev->dev));
+ regulator = devm_regulator_get_optional(led_cdev->dev, "power");
+ if (IS_ERR(regulator)) {
+ if (PTR_ERR(regulator) != -ENODEV) {
+ dev_err(led_cdev->dev, "Cannot get the power supply for %s\n",
+ led_cdev->name);
+ device_unregister(led_cdev->dev);
+ mutex_unlock(&led_cdev->led_access);
+ return PTR_ERR(regulator);
+ }
+ led_cdev->regulator = NULL;
+ } else {
+ led_cdev->regulator = regulator;
+ }
+
if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
ret = led_add_brightness_hw_changed(led_cdev);
if (ret) {
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index 7107cd7e87cf..dab32cf778f2 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -23,6 +23,33 @@ EXPORT_SYMBOL_GPL(leds_list_lock);
LIST_HEAD(leds_list);
EXPORT_SYMBOL_GPL(leds_list);
+static bool __led_need_regulator_update(struct led_classdev *led_cdev,
+ int brightness)
+{
+ bool new_state = (brightness != LED_OFF);
+
+ return led_cdev->regulator && led_cdev->regulator_state != new_state;
+}
+
+static int __led_handle_regulator(struct led_classdev *led_cdev,
+ int brightness)
+{
+ int rc;
+
+ if (__led_need_regulator_update(led_cdev, brightness)) {
+
+ if (brightness != LED_OFF)
+ rc = regulator_enable(led_cdev->regulator);
+ else
+ rc = regulator_disable(led_cdev->regulator);
+ if (rc)
+ return rc;
+
+ led_cdev->regulator_state = (brightness != LED_OFF);
+ }
+ return 0;
+}
+
static int __led_set_brightness(struct led_classdev *led_cdev,
enum led_brightness value)
{
@@ -115,6 +142,8 @@ static void set_brightness_delayed(struct work_struct *ws)
if (ret == -ENOTSUPP)
ret = __led_set_brightness_blocking(led_cdev,
led_cdev->delayed_set_value);
+ __led_handle_regulator(led_cdev, led_cdev->delayed_set_value);
+
if (ret < 0 &&
/* LED HW might have been unplugged, therefore don't warn */
!(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
@@ -256,8 +285,14 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev,
enum led_brightness value)
{
/* Use brightness_set op if available, it is guaranteed not to sleep */
- if (!__led_set_brightness(led_cdev, value))
- return;
+ if (!__led_set_brightness(led_cdev, value)) {
+ /*
+ * if regulator state doesn't need to be changed, that is all/
+ * Otherwise delegate the change to a work queue
+ */
+ if (!__led_need_regulator_update(led_cdev, value))
+ return;
+ }
/* If brightness setting can sleep, delegate it to a work queue task */
led_cdev->delayed_set_value = value;
@@ -280,6 +315,8 @@ EXPORT_SYMBOL_GPL(led_set_brightness_nosleep);
int led_set_brightness_sync(struct led_classdev *led_cdev,
enum led_brightness value)
{
+ int ret;
+
if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
return -EBUSY;
@@ -288,7 +325,11 @@ int led_set_brightness_sync(struct led_classdev *led_cdev,
if (led_cdev->flags & LED_SUSPENDED)
return 0;
- return __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
+ ret = __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
+ if (ret)
+ return ret;
+
+ return __led_handle_regulator(led_cdev, led_cdev->brightness);
}
EXPORT_SYMBOL_GPL(led_set_brightness_sync);
diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
index 47b229469069..5aa5c038bd38 100644
--- a/drivers/leds/leds.h
+++ b/drivers/leds/leds.h
@@ -11,6 +11,7 @@
#include <linux/rwsem.h>
#include <linux/leds.h>
+#include <linux/regulator/consumer.h>
static inline int led_get_brightness(struct led_classdev *led_cdev)
{
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 9b2bf574a17a..bee8e3f8dddd 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -123,6 +123,10 @@ struct led_classdev {
/* Ensures consistent access to the LED Flash Class device */
struct mutex led_access;
+
+ /* regulator */
+ struct regulator *regulator;
+ bool regulator_state;
};
extern int of_led_classdev_register(struct device *parent,
--
2.17.1
Sometimes LEDs are powered by a voltage/current regulator. Describing it
in the device-tree makes it possible for the LED core to enable/disable it
when needed.
Signed-off-by: Jean-Jacques Hiblot <[email protected]>
Reviewed-by: Dan Murphy <[email protected]>
---
Documentation/devicetree/bindings/leds/common.txt | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/Documentation/devicetree/bindings/leds/common.txt b/Documentation/devicetree/bindings/leds/common.txt
index 70876ac11367..f496ec1c1542 100644
--- a/Documentation/devicetree/bindings/leds/common.txt
+++ b/Documentation/devicetree/bindings/leds/common.txt
@@ -61,6 +61,9 @@ Optional properties for child nodes:
- panic-indicator : This property specifies that the LED should be used,
if at all possible, as a panic indicator.
+- power-supply : Is a phandle to a voltage/current regulator used to to power
+ the LED.
+
- trigger-sources : List of devices which should be used as a source triggering
this LED activity. Some LEDs can be related to a specific
device and should somehow indicate its state. E.g. USB 2.0
@@ -106,6 +109,7 @@ gpio-leds {
label = "Status";
linux,default-trigger = "heartbeat";
gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
+ power-supply = <&led_regulator>;
};
usb {
--
2.17.1
Hi Jean,
Thank you for the updated patch set.
I have some more comments below.
On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
> Sometimes LEDs are powered by an external voltage/current regulator. Let
> the LED core know about it. This allows the LED core to turn on or off
> managed power supplies.
>
> Signed-off-by: Jean-Jacques Hiblot <[email protected]>
> Reviewed-by: Dan Murphy <[email protected]>
> ---
> drivers/leds/led-class.c | 15 +++++++++++++
> drivers/leds/led-core.c | 47 +++++++++++++++++++++++++++++++++++++---
> drivers/leds/leds.h | 1 +
> include/linux/leds.h | 4 ++++
> 4 files changed, 64 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 4793e77808e2..cadd43c30d50 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -253,6 +253,7 @@ int of_led_classdev_register(struct device *parent, struct device_node *np,
> {
> char name[LED_MAX_NAME_SIZE];
> int ret;
> + struct regulator *regulator;
>
> ret = led_classdev_next_name(led_cdev->name, name, sizeof(name));
> if (ret < 0)
> @@ -272,6 +273,20 @@ int of_led_classdev_register(struct device *parent, struct device_node *np,
> dev_warn(parent, "Led %s renamed to %s due to name collision",
> led_cdev->name, dev_name(led_cdev->dev));
>
> + regulator = devm_regulator_get_optional(led_cdev->dev, "power");
> + if (IS_ERR(regulator)) {
> + if (PTR_ERR(regulator) != -ENODEV) {
> + dev_err(led_cdev->dev, "Cannot get the power supply for %s\n",
> + led_cdev->name);
> + device_unregister(led_cdev->dev);
> + mutex_unlock(&led_cdev->led_access);
> + return PTR_ERR(regulator);
> + }
> + led_cdev->regulator = NULL;
> + } else {
> + led_cdev->regulator = regulator;
> + }
> +
> if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
> ret = led_add_brightness_hw_changed(led_cdev);
> if (ret) {
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 7107cd7e87cf..dab32cf778f2 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -23,6 +23,33 @@ EXPORT_SYMBOL_GPL(leds_list_lock);
> LIST_HEAD(leds_list);
> EXPORT_SYMBOL_GPL(leds_list);
>
> +static bool __led_need_regulator_update(struct led_classdev *led_cdev,
> + int brightness)
> +{
> + bool new_state = (brightness != LED_OFF);
How about:
bool new_state = !!brightness;
> +
> + return led_cdev->regulator && led_cdev->regulator_state != new_state;
> +}
> +static int __led_handle_regulator(struct led_classdev *led_cdev,
> + int brightness)
> +{
> + int rc;
> +
> + if (__led_need_regulator_update(led_cdev, brightness)) {
> +
> + if (brightness != LED_OFF)
> + rc = regulator_enable(led_cdev->regulator);
> + else
> + rc = regulator_disable(led_cdev->regulator);
> + if (rc)
> + return rc;
> +
> + led_cdev->regulator_state = (brightness != LED_OFF);
> + }
> + return 0;
> +}
Let's have these function names without leading underscores.
> static int __led_set_brightness(struct led_classdev *led_cdev,
> enum led_brightness value)
> {
> @@ -115,6 +142,8 @@ static void set_brightness_delayed(struct work_struct *ws)
> if (ret == -ENOTSUPP)
> ret = __led_set_brightness_blocking(led_cdev,
> led_cdev->delayed_set_value);
> + __led_handle_regulator(led_cdev, led_cdev->delayed_set_value)
If you called it from __led_set_brightness() and
from __led_set_brightness_blocking() you wouldn't need this change here.
> +
> if (ret < 0 &&
> /* LED HW might have been unplugged, therefore don't warn */
> !(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
> @@ -256,8 +285,14 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev,
> enum led_brightness value)
> {
> /* Use brightness_set op if available, it is guaranteed not to sleep */
> - if (!__led_set_brightness(led_cdev, value))
> - return;
> + if (!__led_set_brightness(led_cdev, value)) {
> + /*
> + * if regulator state doesn't need to be changed, that is all/
> + * Otherwise delegate the change to a work queue
> + */
> + if (!__led_need_regulator_update(led_cdev, value))
> + return;
> + }
This change should be also not needed then.
>
> /* If brightness setting can sleep, delegate it to a work queue task */
> led_cdev->delayed_set_value = value;
> @@ -280,6 +315,8 @@ EXPORT_SYMBOL_GPL(led_set_brightness_nosleep);
> int led_set_brightness_sync(struct led_classdev *led_cdev,
> enum led_brightness value)
> {
> + int ret;
> +
> if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
> return -EBUSY;
>
> @@ -288,7 +325,11 @@ int led_set_brightness_sync(struct led_classdev *led_cdev,
> if (led_cdev->flags & LED_SUSPENDED)
> return 0;
>
> - return __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
> + ret = __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
> + if (ret)
> + return ret;
> +
> + return __led_handle_regulator(led_cdev, led_cdev->brightness);
As well as this one.
> }
> EXPORT_SYMBOL_GPL(led_set_brightness_sync);
>
> diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
> index 47b229469069..5aa5c038bd38 100644
> --- a/drivers/leds/leds.h
> +++ b/drivers/leds/leds.h
> @@ -11,6 +11,7 @@
>
> #include <linux/rwsem.h>
> #include <linux/leds.h>
> +#include <linux/regulator/consumer.h>
>
> static inline int led_get_brightness(struct led_classdev *led_cdev)
> {
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 9b2bf574a17a..bee8e3f8dddd 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -123,6 +123,10 @@ struct led_classdev {
>
> /* Ensures consistent access to the LED Flash Class device */
> struct mutex led_access;
> +
> + /* regulator */
> + struct regulator *regulator;
> + bool regulator_state;
> };
>
> extern int of_led_classdev_register(struct device *parent,
>
--
Best regards,
Jacek Anaszewski
On 18/07/2019 14:24, Jacek Anaszewski wrote:
> Hi Jean,
>
> Thank you for the updated patch set.
>
> I have some more comments below.
>
> On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
>>
>> +static bool __led_need_regulator_update(struct led_classdev *led_cdev,
>> + int brightness)
>> +{
>> + bool new_state = (brightness != LED_OFF);
> How about:
>
> bool new_state = !!brightness;
Throughout the code LED_OFF is used when the LED is turned off. I think
it would be more consistent to use it there too.
>
>> +
>> + return led_cdev->regulator && led_cdev->regulator_state != new_state;
>> +}
>> +static int __led_handle_regulator(struct led_classdev *led_cdev,
>> + int brightness)
>> +{
>> + int rc;
>> +
>> + if (__led_need_regulator_update(led_cdev, brightness)) {
>> +
>> + if (brightness != LED_OFF)
>> + rc = regulator_enable(led_cdev->regulator);
>> + else
>> + rc = regulator_disable(led_cdev->regulator);
>> + if (rc)
>> + return rc;
>> +
>> + led_cdev->regulator_state = (brightness != LED_OFF);
>> + }
>> + return 0;
>> +}
> Let's have these function names without leading underscores.
OK.
>
>> static int __led_set_brightness(struct led_classdev *led_cdev,
>> enum led_brightness value)
>> {
>> @@ -115,6 +142,8 @@ static void set_brightness_delayed(struct work_struct *ws)
>> if (ret == -ENOTSUPP)
>> ret = __led_set_brightness_blocking(led_cdev,
>> led_cdev->delayed_set_value);
>> + __led_handle_regulator(led_cdev, led_cdev->delayed_set_value)
> If you called it from __led_set_brightness() and
We cannot call it from __led_set_brightness() because it is supposed not
to block.
JJ
On 7/18/19 3:31 PM, Jean-Jacques Hiblot wrote:
>
> On 18/07/2019 14:24, Jacek Anaszewski wrote:
>> Hi Jean,
>>
>> Thank you for the updated patch set.
>>
>> I have some more comments below.
>>
>> On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
>>> +static bool __led_need_regulator_update(struct led_classdev
>>> *led_cdev,
>>> + int brightness)
>>> +{
>>> + bool new_state = (brightness != LED_OFF);
>> How about:
>>
>> bool new_state = !!brightness;
>
> Throughout the code LED_OFF is used when the LED is turned off. I think
> it would be more consistent to use it there too.
Basically brightness is a scalar and 0 always means off.
We treat enum led_brightness as a legacy type - it is no
longer valid on the whole its span since LED_FULL = 255
was depreciated with addition of max_brightness property.
IMHO use of reverse logic here only hinders code analysis.
>>> +
>>> + return led_cdev->regulator && led_cdev->regulator_state !=
>>> new_state;
>>> +}
>>> +static int __led_handle_regulator(struct led_classdev *led_cdev,
>>> + int brightness)
>>> +{
>>> + int rc;
>>> +
>>> + if (__led_need_regulator_update(led_cdev, brightness)) {
>>> +
>>> + if (brightness != LED_OFF)
>>> + rc = regulator_enable(led_cdev->regulator);
>>> + else
>>> + rc = regulator_disable(led_cdev->regulator);
>>> + if (rc)
>>> + return rc;
>>> +
>>> + led_cdev->regulator_state = (brightness != LED_OFF);
>>> + }
>>> + return 0;
>>> +}
>> Let's have these function names without leading underscores.
> OK.
>>
>>> static int __led_set_brightness(struct led_classdev *led_cdev,
>>> enum led_brightness value)
>>> {
>>> @@ -115,6 +142,8 @@ static void set_brightness_delayed(struct
>>> work_struct *ws)
>>> if (ret == -ENOTSUPP)
>>> ret = __led_set_brightness_blocking(led_cdev,
>>> led_cdev->delayed_set_value);
>>> + __led_handle_regulator(led_cdev, led_cdev->delayed_set_value)
>> If you called it from __led_set_brightness() and
>
> We cannot call it from __led_set_brightness() because it is supposed not
> to block.
You're right. The problematic part is that with regulator handling
we cannot treat the whole brightness setting operation uniformly
for brightness_set op case, i.e. without mediation of a workqueue.
Now you have to fire workqueue in led_set_brightness_nopm()
even for brightness_set() op path, if regulator state needs update.
This is ugly and can be misleading. Can be also error prone and
have non-obvious implications for software blink state transitions.
I think we would first need to improve locking between the workqueue
and led_timer_function(). I proposed a patch [0] over a year
ago.
Only then we could think of adding another asynchronous dependency
to the brightness setting chain.
[0] https://lkml.org/lkml/2018/1/17/1144
--
Best regards,
Jacek Anaszewski
Hi Jacek,
On 18/07/2019 19:49, Jacek Anaszewski wrote:
> On 7/18/19 3:31 PM, Jean-Jacques Hiblot wrote:
>> On 18/07/2019 14:24, Jacek Anaszewski wrote:
>>> Hi Jean,
>>>
>>> Thank you for the updated patch set.
>>>
>>> I have some more comments below.
>>>
>>> On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
>>>> +static bool __led_need_regulator_update(struct led_classdev
>>>> *led_cdev,
>>>> + int brightness)
>>>> +{
>>>> + bool new_state = (brightness != LED_OFF);
>>> How about:
>>>
>>> bool new_state = !!brightness;
>> Throughout the code LED_OFF is used when the LED is turned off. I think
>> it would be more consistent to use it there too.
> Basically brightness is a scalar and 0 always means off.
> We treat enum led_brightness as a legacy type - it is no
> longer valid on the whole its span since LED_FULL = 255
> was depreciated with addition of max_brightness property.
>
> IMHO use of reverse logic here only hinders code analysis.
>
>>>> +
>>>> + return led_cdev->regulator && led_cdev->regulator_state !=
>>>> new_state;
>>>> +}
>>>> +static int __led_handle_regulator(struct led_classdev *led_cdev,
>>>> + int brightness)
>>>> +{
>>>> + int rc;
>>>> +
>>>> + if (__led_need_regulator_update(led_cdev, brightness)) {
>>>> +
>>>> + if (brightness != LED_OFF)
>>>> + rc = regulator_enable(led_cdev->regulator);
>>>> + else
>>>> + rc = regulator_disable(led_cdev->regulator);
>>>> + if (rc)
>>>> + return rc;
>>>> +
>>>> + led_cdev->regulator_state = (brightness != LED_OFF);
>>>> + }
>>>> + return 0;
>>>> +}
>>> Let's have these function names without leading underscores.
>> OK.
>>>> static int __led_set_brightness(struct led_classdev *led_cdev,
>>>> enum led_brightness value)
>>>> {
>>>> @@ -115,6 +142,8 @@ static void set_brightness_delayed(struct
>>>> work_struct *ws)
>>>> if (ret == -ENOTSUPP)
>>>> ret = __led_set_brightness_blocking(led_cdev,
>>>> led_cdev->delayed_set_value);
>>>> + __led_handle_regulator(led_cdev, led_cdev->delayed_set_value)
>>> If you called it from __led_set_brightness() and
>> We cannot call it from __led_set_brightness() because it is supposed not
>> to block.
> You're right. The problematic part is that with regulator handling
> we cannot treat the whole brightness setting operation uniformly
> for brightness_set op case, i.e. without mediation of a workqueue.
>
> Now you have to fire workqueue in led_set_brightness_nopm()
> even for brightness_set() op path, if regulator state needs update.
> This is ugly and can be misleading. Can be also error prone and
> have non-obvious implications for software blink state transitions.
Taking your queue I reworked the series to take better care of the
concurrency issues.
I believe it's in better shape right now.
>
> I think we would first need to improve locking between the workqueue
> and led_timer_function(). I proposed a patch [0] over a year
> ago.
I tried the patch and get a lot of warning because of triggers on
storage devices.
Making led_set_brightness() not callable from a IRQ context, is probably
not the right approach anymore.
JJ
>
> Only then we could think of adding another asynchronous dependency
> to the brightness setting chain.
>
> [0] https://lkml.org/lkml/2018/1/17/1144
>