Re: [PATCH v2 1/2] leds: core: Introduce LED pattern trigger

[Baolin Wang <baolin.wang@linaro.org>]

Hi Jacek,

On 3 August 2018 at 05:21, Jacek Anaszewski <jacek.anaszewski@gmail.com> wrote:
> Hi Baolin,
>
> Thank you for addressing review remarks.
>
> I've played a bit with the interface and I have one conclusion
> regarding pattern parsing, please refer below.
>
> Also one tiny optimization request in pattern_trig_activate().
>
> On 08/01/2018 11:01 AM, Baolin Wang wrote:
>> Some LED controllers have support for autonomously controlling
>> brightness over time, according to some preprogrammed pattern or
>> function.
>>
>> This patch adds pattern trigger that LED device can configure the
>> pattern and trigger it.
>>
>> Signed-off-by: Raphael Teysseyre <rteysseyre@gmail.com>
>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>> ---
>> Changes from v1:
>>  - Use ATTRIBUTE_GROUPS() to define attributes.
>>  - Introduce hardware_pattern flag to determine if software pattern
>>  or hardware pattern.
>>  - Re-implement pattern_trig_store_pattern() function.
>>  - Remove pattern_get() interface.
>>  - Improve comments.
>>  - Other small optimization.
>> ---
>>  .../ABI/testing/sysfs-class-led-trigger-pattern    |   21 ++
>>  drivers/leds/trigger/Kconfig                       |    7 +
>>  drivers/leds/trigger/Makefile                      |    1 +
>>  drivers/leds/trigger/ledtrig-pattern.c             |  273 ++++++++++++++++++++
>>  include/linux/leds.h                               |   16 ++
>>  5 files changed, 318 insertions(+)
>>  create mode 100644 Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>>  create mode 100644 drivers/leds/trigger/ledtrig-pattern.c
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-pattern b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>> new file mode 100644
>> index 0000000..f9a4ac0
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>> @@ -0,0 +1,21 @@
>> +What:                /sys/class/leds/<led>/pattern
>> +Date:                August 2018
>> +KernelVersion:       4.19
>> +Description:
>> +             Specify a pattern for the LED, for LED hardware that support
>> +             altering the brightness as a function of time.
>> +
>> +             The pattern is given by a series of tuples, of brightness and
>> +             duration (ms). The LED is expected to traverse the series and
>> +             each brightness value for the specified duration. Duration of
>> +             0 means brightness should immediately change to new value.
>> +
>> +             The format of the pattern values should be:
>> +             "brightness_1 duration_1, brightness_2 duration_2, brightness_3
>> +             duration_3 ...".
>> +
>> +What:                /sys/class/leds/<led>/repeat
>> +Date:                August 2018
>> +KernelVersion:       4.19
>> +Description:
>> +             Specify a pattern repeat number. 0 means repeat indefinitely.
>> diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
>> index 4018af7..b76fc3c 100644
>> --- a/drivers/leds/trigger/Kconfig
>> +++ b/drivers/leds/trigger/Kconfig
>> @@ -129,4 +129,11 @@ config LEDS_TRIGGER_NETDEV
>>         This allows LEDs to be controlled by network device activity.
>>         If unsure, say Y.
>>
>> +config LEDS_TRIGGER_PATTERN
>> +     tristate "LED Pattern Trigger"
>> +     help
>> +       This allows LEDs to be controlled by a software or hardware pattern
>> +       which is a series of tuples, of brightness and duration (ms).
>> +       If unsure, say N
>> +
>>  endif # LEDS_TRIGGERS
>> diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
>> index f3cfe19..9bcb64e 100644
>> --- a/drivers/leds/trigger/Makefile
>> +++ b/drivers/leds/trigger/Makefile
>> @@ -13,3 +13,4 @@ obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT)        += ledtrig-transient.o
>>  obj-$(CONFIG_LEDS_TRIGGER_CAMERA)    += ledtrig-camera.o
>>  obj-$(CONFIG_LEDS_TRIGGER_PANIC)     += ledtrig-panic.o
>>  obj-$(CONFIG_LEDS_TRIGGER_NETDEV)    += ledtrig-netdev.o
>> +obj-$(CONFIG_LEDS_TRIGGER_PATTERN)   += ledtrig-pattern.o
>> diff --git a/drivers/leds/trigger/ledtrig-pattern.c b/drivers/leds/trigger/ledtrig-pattern.c
>> new file mode 100644
>> index 0000000..006874b
>> --- /dev/null
>> +++ b/drivers/leds/trigger/ledtrig-pattern.c
>> @@ -0,0 +1,273 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +/*
>> + * LED pattern trigger
>> + *
>> + * Idea discussed with Pavel Machek. Raphael Teysseyre implemented
>> + * the first version, Baolin Wang simplified and improved the approach.
>> + */
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/leds.h>
>> +#include <linux/module.h>
>> +#include <linux/mutex.h>
>> +#include <linux/slab.h>
>> +#include <linux/timer.h>
>> +
>> +#define MAX_PATTERNS         1024
>> +#define PATTERN_SEPARATOR    ","
>> +
>> +struct pattern_trig_data {
>> +     struct led_classdev *led_cdev;
>> +     struct led_pattern patterns[MAX_PATTERNS];
>> +     struct led_pattern *curr;
>> +     struct led_pattern *next;
>> +     struct mutex lock;
>> +     u32 npatterns;
>> +     u32 repeat;
>> +     bool is_indefinite;
>> +     bool hardware_pattern;
>> +     struct timer_list timer;
>> +};
>> +
>> +static void pattern_trig_update_patterns(struct pattern_trig_data *data)
>> +{
>> +     data->curr = data->next;
>> +     if (!data->is_indefinite && data->curr == data->patterns)
>> +             data->repeat--;
>> +
>> +     if (data->next == data->patterns + data->npatterns - 1)
>> +             data->next = data->patterns;
>> +     else
>> +             data->next++;
>> +}
>> +
>> +static void pattern_trig_timer_function(struct timer_list *t)
>> +{
>> +     struct pattern_trig_data *data = from_timer(data, t, timer);
>> +
>> +     mutex_lock(&data->lock);
>> +
>> +     if (!data->is_indefinite && !data->repeat) {
>> +             mutex_unlock(&data->lock);
>> +             return;
>> +     }
>> +
>> +     led_set_brightness(data->led_cdev, data->curr->brightness);
>> +     mod_timer(&data->timer, jiffies + msecs_to_jiffies(data->curr->delta_t));
>> +     pattern_trig_update_patterns(data);
>> +
>> +     mutex_unlock(&data->lock);
>> +}
>> +
>> +static int pattern_trig_start_pattern(struct pattern_trig_data *data,
>> +                                   struct led_classdev *led_cdev)
>> +{
>> +     if (!data->npatterns)
>> +             return 0;
>> +
>> +     if (data->hardware_pattern) {
>> +             return led_cdev->pattern_set(led_cdev, data->patterns,
>> +                                          data->npatterns, data->repeat);
>> +     }
>> +
>> +     data->curr = data->patterns;
>> +     data->next = data->patterns + 1;
>> +     data->timer.expires = jiffies;
>> +     add_timer(&data->timer);
>> +
>> +     return 0;
>> +}
>> +
>> +static ssize_t pattern_trig_show_repeat(struct device *dev,
>> +                                     struct device_attribute *attr,
>> +                                     char *buf)
>> +{
>> +     struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +     struct pattern_trig_data *data = led_cdev->trigger_data;
>> +     u32 repeat;
>> +
>> +     mutex_lock(&data->lock);
>> +
>> +     repeat = data->repeat;
>> +
>> +     mutex_unlock(&data->lock);
>> +
>> +     return scnprintf(buf, PAGE_SIZE, "%u\n", repeat);
>> +}
>> +
>> +static ssize_t pattern_trig_store_repeat(struct device *dev,
>> +                                      struct device_attribute *attr,
>> +                                      const char *buf, size_t count)
>> +{
>> +     struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +     struct pattern_trig_data *data = led_cdev->trigger_data;
>> +     unsigned long res;
>> +     int err;
>> +
>> +     err = kstrtoul(buf, 10, &res);
>> +     if (err)
>> +             return err;
>> +
>> +     if (!data->hardware_pattern)
>> +             del_timer_sync(&data->timer);
>> +
>> +     mutex_lock(&data->lock);
>> +
>> +     data->repeat = res;
>> +
>> +     /* 0 means repeat indefinitely */
>> +     if (!data->repeat)
>> +             data->is_indefinite = true;
>> +     else
>> +             data->is_indefinite = false;
>> +
>> +     err = pattern_trig_start_pattern(data, led_cdev);
>> +
>> +     mutex_unlock(&data->lock);
>> +     return err < 0 ? err : count;;
>> +}
>> +
>> +static DEVICE_ATTR(repeat, 0644, pattern_trig_show_repeat,
>> +                pattern_trig_store_repeat);
>> +
>> +static ssize_t pattern_trig_show_pattern(struct device *dev,
>> +                                      struct device_attribute *attr,
>> +                                      char *buf)
>> +{
>> +     struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +     struct pattern_trig_data *data = led_cdev->trigger_data;
>> +     ssize_t count = 0;
>> +     int i;
>> +
>> +     mutex_lock(&data->lock);
>> +
>> +     if (!data->npatterns)
>> +             goto out;
>> +
>> +     for (i = 0; i < data->npatterns; i++) {
>> +             count += scnprintf(buf + count, PAGE_SIZE - count,
>> +                                "%d %d" PATTERN_SEPARATOR,
>> +                                data->patterns[i].brightness,
>> +                                data->patterns[i].delta_t);
>> +     }
>> +
>> +     buf[count - 1] = '\n';
>> +
>> +out:
>> +     mutex_unlock(&data->lock);
>> +     return count;
>> +}
>> +
>> +static ssize_t pattern_trig_store_pattern(struct device *dev,
>> +                                       struct device_attribute *attr,
>> +                                       const char *buf, size_t count)
>> +{
>> +     struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +     struct pattern_trig_data *data = led_cdev->trigger_data;
>> +     int cr, ccount, offset = 0, err = 0;
>> +
>> +     if (!data->hardware_pattern)
>> +             del_timer_sync(&data->timer);
>> +
>> +     mutex_lock(&data->lock);
>> +
>> +     data->npatterns = 0;
>> +     while (offset < count - 1 && data->npatterns < MAX_PATTERNS) {
>> +             cr = 0;
>> +             ccount = sscanf(buf + offset, "%d %d " PATTERN_SEPARATOR "%n",
>> +                             &data->patterns[data->npatterns].brightness,
>> +                             &data->patterns[data->npatterns].delta_t, &cr);
>
> In case user makes a typo while constructing list of pattern tuples,
> e.g. he forgets a comma, the pattern gets silently truncated.
>
> User is able to detect the truncation by reading pattern file,
> but it is not an immediate feedback anyway.
>
> I propose that pattern format should require number of tuples in the
> first position which would allow to get rid of this ambiguity, since
> we could verify if the number of parsed tuples is as intended.

OK, I understand your concern. I will fix the issue without
introducing another pattern number. So I will not use a comma to
separate the patterns and change the pattern format as:
brightness1 time1 brightness2 time2 brightness3 time3 brightness4 time4 ...

Then we will easy to check out errors if user gives one incorrect
pattern string.

>
>> +             if (ccount != 2) {
>> +                     err = -EINVAL;
>> +                     goto out;
>> +             }
>> +
>> +             offset += cr;
>> +             data->npatterns++;
>> +             /* end of pattern */
>> +             if (!cr)
>> +                     break;
>> +     }
>> +
>> +     err = pattern_trig_start_pattern(data, led_cdev);
>> +
>> +out:
>> +     mutex_unlock(&data->lock);
>> +     return err < 0 ? err : count;
>> +}
>> +
>> +static DEVICE_ATTR(pattern, 0644, pattern_trig_show_pattern,
>> +                pattern_trig_store_pattern);
>> +
>> +static struct attribute *pattern_trig_attrs[] = {
>> +     &dev_attr_pattern.attr,
>> +     &dev_attr_repeat.attr,
>> +     NULL
>> +};
>> +ATTRIBUTE_GROUPS(pattern_trig);
>> +
>> +static int pattern_trig_activate(struct led_classdev *led_cdev)
>> +{
>> +     struct pattern_trig_data *data;
>> +
>> +     data = kzalloc(sizeof(*data), GFP_KERNEL);
>> +     if (!data)
>> +             return -ENOMEM;
>> +
>> +     if (led_cdev->pattern_set && led_cdev->pattern_clear)
>> +             data->hardware_pattern = true;
>
> Instead of introducing hardware_pattern boolean, let's log warning
> message here in case:
>
> if (!!led_cdev->pattern_set ^ !!led_cdev->pattern_clear)
>         dev_warn(led_cdev->dev, "Hardware pattern ops validation failed");
>
> And later, having this validation behind us, we can be sure that we have
> hardware pattern support when led_cdev->pattern_set is initialized.

Hmm, I am not sure I catch your points. If we remove the
hardware_pattern boolean, we still need to add check before
'del_timer_sync(&data->timer)' (In hardware pattern mode, we do not
need to delete the timer), also we still need to add check before
issuing pattern_set()/pattern_clear().

So I think introducing one boolean will make code easy to understand
what pattern mode (software pattern or hardware pattern) is using.
Thanks.

>
>> +     else
>> +             data->hardware_pattern = false;
>> +
>> +     data->is_indefinite = true;
>> +     mutex_init(&data->lock);
>> +     data->led_cdev = led_cdev;
>> +     led_set_trigger_data(led_cdev, data);
>> +     timer_setup(&data->timer, pattern_trig_timer_function, 0);
>> +     led_cdev->activated = true;
>> +
>> +     return 0;
>> +}
>> +
>> +static void pattern_trig_deactivate(struct led_classdev *led_cdev)
>> +{
>> +     struct pattern_trig_data *data = led_cdev->trigger_data;
>> +
>> +     if (!led_cdev->activated)
>> +             return;
>> +
>> +     if (data->hardware_pattern)
>> +             led_cdev->pattern_clear(led_cdev);
>> +     else
>> +             del_timer_sync(&data->timer);
>> +
>> +     led_set_brightness(led_cdev, LED_OFF);
>> +     kfree(data);
>> +     led_cdev->activated = false;
>> +}
>> +
>> +static struct led_trigger pattern_led_trigger = {
>> +     .name = "pattern",
>> +     .activate = pattern_trig_activate,
>> +     .deactivate = pattern_trig_deactivate,
>> +     .groups = pattern_trig_groups,
>> +};
>> +
>> +static int __init pattern_trig_init(void)
>> +{
>> +     return led_trigger_register(&pattern_led_trigger);
>> +}
>> +
>> +static void __exit pattern_trig_exit(void)
>> +{
>> +     led_trigger_unregister(&pattern_led_trigger);
>> +}
>> +
>> +module_init(pattern_trig_init);
>> +module_exit(pattern_trig_exit);
>> +
>> +MODULE_AUTHOR("Raphael Teysseyre <rteysseyre@gmail.com");
>> +MODULE_AUTHOR("Baolin Wang <baolin.wang@linaro.org");
>> +MODULE_DESCRIPTION("LED Pattern trigger");
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index 834683d..c54712c 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -22,6 +22,7 @@
>>  #include <linux/workqueue.h>
>>
>>  struct device;
>> +struct led_pattern;
>>  /*
>>   * LED Core
>>   */
>> @@ -88,6 +89,11 @@ struct led_classdev {
>>                                    unsigned long *delay_on,
>>                                    unsigned long *delay_off);
>>
>> +     int (*pattern_set)(struct led_classdev *led_cdev,
>> +                        struct led_pattern *pattern, int len,
>> +                        unsigned repeat);
>> +     int (*pattern_clear)(struct led_classdev *led_cdev);
>> +
>>       struct device           *dev;
>>       const struct attribute_group    **groups;
>>
>> @@ -472,4 +478,14 @@ static inline void led_classdev_notify_brightness_hw_changed(
>>       struct led_classdev *led_cdev, enum led_brightness brightness) { }
>>  #endif
>>
>> +/**
>> + * struct led_pattern - brightness value in a pattern
>> + * @delta_t: delay until next entry, in milliseconds
>> + * @brightness: brightness at time = 0
>> + */
>> +struct led_pattern {
>> +     int delta_t;
>> +     int brightness;
>> +};
>> +
>>  #endif               /* __LINUX_LEDS_H_INCLUDED */
>>
>
> --
> Best regards,
> Jacek Anaszewski



-- 
Baolin Wang
Best Regards