Re: [PATCH v3] led-class: always implement blinking

From: Johannes Berg
Date: Fri Sep 24 2010 - 05:29:34 EST

On Thu, 2010-09-23 at 15:35 -0700, Andrew Morton wrote:

> > v3: - make LEDS_CLASS a bool rather than tristate
> > because LEDS_TRIGGERS now depends on symbols
> > it exports
>
> `make oldconfig' says
>
> boolean symbol LEDS_CLASS tested for 'm'? test forced to 'n'

Thanks, that must be from

comment "rt2x00 leds support disabled due to modularized LEDS_CLASS and built-in rt2x00"
depends on RT2X00_LIB=y && LEDS_CLASS=m

New patch below.

johannes

Subject: led-class: always implement blinking

From: Johannes Berg <johannes.berg@xxxxxxxxx>

Currently, blinking LEDs can be awkward because it is
not guaranteed that all LEDs implement blinking. The
trigger that wants it to blink then needs to implement
its own timer solution.

Rather than require that, add led_blink_set() API that
triggers can use. This function will attempt to use hw
blinking, but if that fails implements a timer for it.
To stop blinking again, brightness_set() also needs to
be wrapped into API that will stop the software blink.

As a result of this, the timer trigger becomes a very
trivial one, and hopefully we can finally see triggers
using blinking as well because it's always easy to use.

Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
v2: - update documentation
- use documented way of turning blinking off
by setting brightness to 0 rather than by
setting delays to (0, 0)
- add API to start blinking, set brightness
(the latter will also stop sw blinking)
v3: - make LEDS_CLASS a bool rather than tristate
because LEDS_TRIGGERS now depends on symbols
it exports
v4: - remove LEDS_CLASS=m comparison from rt2x00

Documentation/leds-class.txt | 19 +++--
drivers/leds/Kconfig | 2
drivers/leds/led-class.c | 105 ++++++++++++++++++++++++++++++
drivers/leds/led-triggers.c | 2
drivers/leds/ledtrig-timer.c | 124 ++----------------------------------
drivers/net/wireless/rt2x00/Kconfig | 3
include/linux/leds.h | 47 ++++++++++++-
7 files changed, 170 insertions(+), 132 deletions(-)

--- wireless-testing.orig/drivers/leds/ledtrig-timer.c 2010-09-24 11:23:55.000000000 +0200
+++ wireless-testing/drivers/leds/ledtrig-timer.c 2010-09-24 11:23:56.000000000 +0200
@@ -12,73 +12,25 @@
*/

#include <linux/module.h>
-#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/init.h>
-#include <linux/list.h>
-#include <linux/spinlock.h>
#include <linux/device.h>
-#include <linux/sysdev.h>
-#include <linux/timer.h>
#include <linux/ctype.h>
#include <linux/leds.h>
-#include <linux/slab.h>
#include "leds.h"

-struct timer_trig_data {
- int brightness_on; /* LED brightness during "on" period.
- * (LED_OFF < brightness_on <= LED_FULL)
- */
- unsigned long delay_on; /* milliseconds on */
- unsigned long delay_off; /* milliseconds off */
- struct timer_list timer;
-};
-
-static void led_timer_function(unsigned long data)
-{
- struct led_classdev *led_cdev = (struct led_classdev *) data;
- struct timer_trig_data *timer_data = led_cdev->trigger_data;
- unsigned long brightness;
- unsigned long delay;
-
- if (!timer_data->delay_on || !timer_data->delay_off) {
- led_set_brightness(led_cdev, LED_OFF);
- return;
- }
-
- brightness = led_get_brightness(led_cdev);
- if (!brightness) {
- /* Time to switch the LED on. */
- brightness = timer_data->brightness_on;
- delay = timer_data->delay_on;
- } else {
- /* Store the current brightness value to be able
- * to restore it when the delay_off period is over.
- */
- timer_data->brightness_on = brightness;
- brightness = LED_OFF;
- delay = timer_data->delay_off;
- }
-
- led_set_brightness(led_cdev, brightness);
-
- mod_timer(&timer_data->timer, jiffies + msecs_to_jiffies(delay));
-}
-
static ssize_t led_delay_on_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct led_classdev *led_cdev = dev_get_drvdata(dev);
- struct timer_trig_data *timer_data = led_cdev->trigger_data;

- return sprintf(buf, "%lu\n", timer_data->delay_on);
+ return sprintf(buf, "%lu\n", led_cdev->blink_delay_on);
}

static ssize_t led_delay_on_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t size)
{
struct led_classdev *led_cdev = dev_get_drvdata(dev);
- struct timer_trig_data *timer_data = led_cdev->trigger_data;
int ret = -EINVAL;
char *after;
unsigned long state = simple_strtoul(buf, &after, 10);
@@ -88,21 +40,7 @@ static ssize_t led_delay_on_store(struct
count++;

if (count == size) {
- if (timer_data->delay_on != state) {
- /* the new value differs from the previous */
- timer_data->delay_on = state;
-
- /* deactivate previous settings */
- del_timer_sync(&timer_data->timer);
-
- /* try to activate hardware acceleration, if any */
- if (!led_cdev->blink_set ||
- led_cdev->blink_set(led_cdev,
- &timer_data->delay_on, &timer_data->delay_off)) {
- /* no hardware acceleration, blink via timer */
- mod_timer(&timer_data->timer, jiffies + 1);
- }
- }
+ led_blink_set(led_cdev, &state, &led_cdev->blink_delay_off);
ret = count;
}

@@ -113,16 +51,14 @@ static ssize_t led_delay_off_show(struct
struct device_attribute *attr, char *buf)
{
struct led_classdev *led_cdev = dev_get_drvdata(dev);
- struct timer_trig_data *timer_data = led_cdev->trigger_data;

- return sprintf(buf, "%lu\n", timer_data->delay_off);
+ return sprintf(buf, "%lu\n", led_cdev->blink_delay_off);
}

static ssize_t led_delay_off_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t size)
{
struct led_classdev *led_cdev = dev_get_drvdata(dev);
- struct timer_trig_data *timer_data = led_cdev->trigger_data;
int ret = -EINVAL;
char *after;
unsigned long state = simple_strtoul(buf, &after, 10);
@@ -132,21 +68,7 @@ static ssize_t led_delay_off_store(struc
count++;

if (count == size) {
- if (timer_data->delay_off != state) {
- /* the new value differs from the previous */
- timer_data->delay_off = state;
-
- /* deactivate previous settings */
- del_timer_sync(&timer_data->timer);
-
- /* try to activate hardware acceleration, if any */
- if (!led_cdev->blink_set ||
- led_cdev->blink_set(led_cdev,
- &timer_data->delay_on, &timer_data->delay_off)) {
- /* no hardware acceleration, blink via timer */
- mod_timer(&timer_data->timer, jiffies + 1);
- }
- }
+ led_blink_set(led_cdev, &led_cdev->blink_delay_on, &state);
ret = count;
}

@@ -158,60 +80,34 @@ static DEVICE_ATTR(delay_off, 0644, led_

static void timer_trig_activate(struct led_classdev *led_cdev)
{
- struct timer_trig_data *timer_data;
int rc;

- timer_data = kzalloc(sizeof(struct timer_trig_data), GFP_KERNEL);
- if (!timer_data)
- return;
-
- timer_data->brightness_on = led_get_brightness(led_cdev);
- if (timer_data->brightness_on == LED_OFF)
- timer_data->brightness_on = led_cdev->max_brightness;
- led_cdev->trigger_data = timer_data;
-
- init_timer(&timer_data->timer);
- timer_data->timer.function = led_timer_function;
- timer_data->timer.data = (unsigned long) led_cdev;
+ led_cdev->trigger_data = NULL;

rc = device_create_file(led_cdev->dev, &dev_attr_delay_on);
if (rc)
- goto err_out;
+ return;
rc = device_create_file(led_cdev->dev, &dev_attr_delay_off);
if (rc)
goto err_out_delayon;

- /* If there is hardware support for blinking, start one
- * user friendly blink rate chosen by the driver.
- */
- if (led_cdev->blink_set)
- led_cdev->blink_set(led_cdev,
- &timer_data->delay_on, &timer_data->delay_off);
+ led_cdev->trigger_data = (void *)1;

return;

err_out_delayon:
device_remove_file(led_cdev->dev, &dev_attr_delay_on);
-err_out:
- led_cdev->trigger_data = NULL;
- kfree(timer_data);
}

static void timer_trig_deactivate(struct led_classdev *led_cdev)
{
- struct timer_trig_data *timer_data = led_cdev->trigger_data;
- unsigned long on = 0, off = 0;
-
- if (timer_data) {
+ if (led_cdev->trigger_data) {
device_remove_file(led_cdev->dev, &dev_attr_delay_on);
device_remove_file(led_cdev->dev, &dev_attr_delay_off);
- del_timer_sync(&timer_data->timer);
- kfree(timer_data);
}

- /* If there is hardware support for blinking, stop it */
- if (led_cdev->blink_set)
- led_cdev->blink_set(led_cdev, &on, &off);
+ /* Stop blinking */
+ led_brightness_set(led_cdev, LED_OFF);
}

static struct led_trigger timer_led_trigger = {
--- wireless-testing.orig/drivers/leds/led-class.c 2010-09-24 11:23:55.000000000 +0200
+++ wireless-testing/drivers/leds/led-class.c 2010-09-24 11:23:56.000000000 +0200
@@ -81,6 +81,79 @@ static struct device_attribute led_class
__ATTR_NULL,
};

+static void led_timer_function(unsigned long data)
+{
+ struct led_classdev *led_cdev = (void *)data;
+ unsigned long brightness;
+ unsigned long delay;
+
+ if (!led_cdev->blink_delay_on || !led_cdev->blink_delay_off) {
+ led_set_brightness(led_cdev, LED_OFF);
+ return;
+ }
+
+ brightness = led_get_brightness(led_cdev);
+ if (!brightness) {
+ /* Time to switch the LED on. */
+ brightness = led_cdev->blink_brightness;
+ delay = led_cdev->blink_delay_on;
+ } else {
+ /* Store the current brightness value to be able
+ * to restore it when the delay_off period is over.
+ */
+ led_cdev->blink_brightness = brightness;
+ brightness = LED_OFF;
+ delay = led_cdev->blink_delay_off;
+ }
+
+ led_set_brightness(led_cdev, brightness);
+
+ mod_timer(&led_cdev->blink_timer, jiffies + msecs_to_jiffies(delay));
+}
+
+static void led_stop_software_blink(struct led_classdev *led_cdev)
+{
+ /* deactivate previous settings */
+ del_timer_sync(&led_cdev->blink_timer);
+ led_cdev->blink_delay_on = 0;
+ led_cdev->blink_delay_off = 0;
+}
+
+static void led_set_software_blink(struct led_classdev *led_cdev,
+ unsigned long delay_on,
+ unsigned long delay_off)
+{
+ int current_brightness;
+
+ current_brightness = led_get_brightness(led_cdev);
+ if (current_brightness)
+ led_cdev->blink_brightness = current_brightness;
+ if (!led_cdev->blink_brightness)
+ led_cdev->blink_brightness = led_cdev->max_brightness;
+
+ if (delay_on == led_cdev->blink_delay_on &&
+ delay_off == led_cdev->blink_delay_off)
+ return;
+
+ led_stop_software_blink(led_cdev);
+
+ led_cdev->blink_delay_on = delay_on;
+ led_cdev->blink_delay_off = delay_off;
+
+ /* never on - don't blink */
+ if (!delay_on)
+ return;
+
+ /* never off - just set to brightness */
+ if (!delay_off) {
+ led_set_brightness(led_cdev, led_cdev->blink_brightness);
+ return;
+ }
+
+ mod_timer(&led_cdev->blink_timer, jiffies + 1);
+}
+
+
/**
* led_classdev_suspend - suspend an led_classdev.
* @led_cdev: the led_classdev to suspend.
@@ -148,6 +221,10 @@ int led_classdev_register(struct device

led_update_brightness(led_cdev);

+ init_timer(&led_cdev->blink_timer);
+ led_cdev->blink_timer.function = led_timer_function;
+ led_cdev->blink_timer.data = (unsigned long)led_cdev;
+
#ifdef CONFIG_LEDS_TRIGGERS
led_trigger_set_default(led_cdev);
#endif
@@ -157,7 +234,6 @@ int led_classdev_register(struct device

return 0;
}
-
EXPORT_SYMBOL_GPL(led_classdev_register);

/**
@@ -175,6 +251,9 @@ void led_classdev_unregister(struct led_
up_write(&led_cdev->trigger_lock);
#endif

+ /* Stop blinking */
+ led_brightness_set(led_cdev, LED_OFF);
+
device_unregister(led_cdev->dev);

down_write(&leds_list_lock);
@@ -183,6 +262,30 @@ void led_classdev_unregister(struct led_
}
EXPORT_SYMBOL_GPL(led_classdev_unregister);

+void led_blink_set(struct led_classdev *led_cdev,
+ unsigned long *delay_on,
+ unsigned long *delay_off)
+{
+ if (led_cdev->blink_set &&
+ led_cdev->blink_set(led_cdev, delay_on, delay_off))
+ return;
+
+ /* blink with 1 Hz as default if nothing specified */
+ if (!*delay_on && !*delay_off)
+ *delay_on = *delay_off = 500;
+
+ led_set_software_blink(led_cdev, *delay_on, *delay_off);
+}
+EXPORT_SYMBOL(led_blink_set);
+
+void led_brightness_set(struct led_classdev *led_cdev,
+ enum led_brightness brightness)
+{
+ led_stop_software_blink(led_cdev);
+ led_cdev->brightness_set(led_cdev, brightness);
+}
+EXPORT_SYMBOL(led_brightness_set);
+
static int __init leds_init(void)
{
leds_class = class_create(THIS_MODULE, "leds");
--- wireless-testing.orig/drivers/leds/led-triggers.c 2010-09-24 11:23:55.000000000 +0200
+++ wireless-testing/drivers/leds/led-triggers.c 2010-09-24 11:23:56.000000000 +0200
@@ -113,7 +113,7 @@ void led_trigger_set(struct led_classdev
if (led_cdev->trigger->deactivate)
led_cdev->trigger->deactivate(led_cdev);
led_cdev->trigger = NULL;
- led_set_brightness(led_cdev, LED_OFF);
+ led_brightness_set(led_cdev, LED_OFF);
}
if (trigger) {
write_lock_irqsave(&trigger->leddev_list_lock, flags);
--- wireless-testing.orig/include/linux/leds.h 2010-09-24 11:23:54.000000000 +0200
+++ wireless-testing/include/linux/leds.h 2010-09-24 11:23:56.000000000 +0200
@@ -15,6 +15,7 @@
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/rwsem.h>
+#include <linux/timer.h>

struct device;
/*
@@ -45,10 +46,14 @@ struct led_classdev {
/* Get LED brightness level */
enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);

- /* Activate hardware accelerated blink, delays are in
- * miliseconds and if none is provided then a sensible default
- * should be chosen. The call can adjust the timings if it can't
- * match the values specified exactly. */
+ /*
+ * Activate hardware accelerated blink, delays are in milliseconds
+ * and if both are zero then a sensible default should be chosen.
+ * The call should adjust the timings in that case and if it can't
+ * match the values specified exactly.
+ * Deactivate blinking again when the brightness is set to a fixed
+ * value via the brightness_set() callback.
+ */
int (*blink_set)(struct led_classdev *led_cdev,
unsigned long *delay_on,
unsigned long *delay_off);
@@ -57,6 +62,10 @@ struct led_classdev {
struct list_head node; /* LED Device list */
const char *default_trigger; /* Trigger to use */

+ unsigned long blink_delay_on, blink_delay_off;
+ struct timer_list blink_timer;
+ int blink_brightness;
+
#ifdef CONFIG_LEDS_TRIGGERS
/* Protects the trigger data below */
struct rw_semaphore trigger_lock;
@@ -73,6 +82,36 @@ extern void led_classdev_unregister(stru
extern void led_classdev_suspend(struct led_classdev *led_cdev);
extern void led_classdev_resume(struct led_classdev *led_cdev);

+/**
+ * led_blink_set - set blinking with software fallback
+ * @led_cdev: the LED to start blinking
+ * @delay_on: the time it should be on (in ms)
+ * @delay_off: the time it should ble off (in ms)
+ *
+ * This function makes the LED blink, attempting to use the
+ * hardware acceleration if possible, but falling back to
+ * software blinking if there is no hardware blinking or if
+ * the LED refuses the passed values.
+ *
+ * Note that if software blinking is active, simply calling
+ * led_cdev->brightness_set() will not stop the blinking,
+ * use led_classdev_brightness_set() instead.
+ */
+extern void led_blink_set(struct led_classdev *led_cdev,
+ unsigned long *delay_on,
+ unsigned long *delay_off);
+/**
+ * led_brightness_set - set LED brightness
+ * @led_cdev: the LED to set
+ * @brightness: the brightness to set it to
+ *
+ * Set an LED's brightness, and, if necessary, cancel the
+ * software blink timer that implements blinking when the
+ * hardware doesn't.
+ */
+extern void led_brightness_set(struct led_classdev *led_cdev,
+ enum led_brightness brightness);
+
/*
* LED Triggers
*/
--- wireless-testing.orig/Documentation/leds-class.txt 2010-09-24 11:23:54.000000000 +0200
+++ wireless-testing/Documentation/leds-class.txt 2010-09-24 11:23:56.000000000 +0200
@@ -60,15 +60,18 @@ Hardware accelerated blink of LEDs

Some LEDs can be programmed to blink without any CPU interaction. To
support this feature, a LED driver can optionally implement the
-blink_set() function (see <linux/leds.h>). If implemented, triggers can
-attempt to use it before falling back to software timers. The blink_set()
-function should return 0 if the blink setting is supported, or -EINVAL
-otherwise, which means that LED blinking will be handled by software.
+blink_set() function (see <linux/leds.h>). To set an LED to blinking,
+however, it is better to use use the API function led_blink_set(),
+as it will check and implement software fallback if necessary.

-The blink_set() function should choose a user friendly blinking
-value if it is called with *delay_on==0 && *delay_off==0 parameters. In
-this case the driver should give back the chosen value through delay_on
-and delay_off parameters to the leds subsystem.
+To turn off blinking again, use the API function led_brightness_set()
+as that will not just set the LED brightness but also stop any software
+timers that may have been required for blinking.
+
+The blink_set() function should choose a user friendly blinking value
+if it is called with *delay_on==0 && *delay_off==0 parameters. In this
+case the driver should give back the chosen value through delay_on and
+delay_off parameters to the leds subsystem.

Setting the brightness to zero with brightness_set() callback function
should completely turn off the LED and cancel the previously programmed
--- wireless-testing.orig/drivers/leds/Kconfig 2010-09-24 11:23:55.000000000 +0200
+++ wireless-testing/drivers/leds/Kconfig 2010-09-24 11:23:56.000000000 +0200
@@ -10,7 +10,7 @@ menuconfig NEW_LEDS
if NEW_LEDS

config LEDS_CLASS
- tristate "LED Class Support"
+ bool "LED Class Support"
help
This option enables the led sysfs class in /sys/class/leds. You'll
need this to do anything useful with LEDs. If unsure, say N.
--- wireless-testing.orig/drivers/net/wireless/rt2x00/Kconfig 2010-09-24 11:25:35.000000000 +0200
+++ wireless-testing/drivers/net/wireless/rt2x00/Kconfig 2010-09-24 11:26:09.000000000 +0200
@@ -221,9 +221,6 @@ config RT2X00_LIB_LEDS
boolean
default y if (RT2X00_LIB=y && LEDS_CLASS=y) || (RT2X00_LIB=m && LEDS_CLASS!=n)

-comment "rt2x00 leds support disabled due to modularized LEDS_CLASS and built-in rt2x00"
- depends on RT2X00_LIB=y && LEDS_CLASS=m
-
config RT2X00_LIB_DEBUGFS
bool "Ralink debugfs support"
depends on RT2X00_LIB && MAC80211_DEBUGFS


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