Re: [PATCH v14 1/2] leds: core: Introduce LED pattern trigger

[Jacek Anaszewski]

Hi Baolin,

On 10/03/2018 03:21 AM, Baolin Wang wrote:
> Hi Jacek,
> 
> On 3 October 2018 at 04:25, Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx> wrote:
>> Hi Baolin,
>>
>> Thank you for the v14. We'll probably need v15, though :-)
>>
>> I added the comments in the code below.
>>
>> On 10/02/2018 05:43 PM, Baolin Wang wrote:
>>> This patch adds one new led trigger that LED device can configure
>>> the software or hardware pattern and trigger it.
>>>
>>> Consumers can write 'pattern' file to enable the software pattern
>>> which alters the brightness for the specified duration with one
>>> software timer.
>>>
>>> Moreover consumers can write 'hw_pattern' file to enable the hardware
>>> pattern for some LED controllers which can autonomously control
>>> brightness over time, according to some preprogrammed hardware
>>> patterns.
>>>
>>> Signed-off-by: Raphael Teysseyre <rteysseyre@xxxxxxxxx>
>>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
>>> ---
>>> Changes from v13:
>>>  - Add duration validation for gradual dimming.
>>>  - Coding style optimization.
>>>
>>> Changes from v12:
>>>  - Add gradual dimming support for software pattern.
>>>
>>> Changes from v11:
>>>  - Change -1 means repeat indefinitely.
>>>
>>> Changes from v10:
>>>  - Change 'int' to 'u32' for delta_t field.
>>>
>>> Changes from v9:
>>>  - None.
>>>
>>> Changes from v8:
>>>  - None.
>>>
>>> Changes from v7:
>>>  - Move the SC27XX hardware patterns description into its own ABI file.
>>>
>>> Changes from v6:
>>>  - Improve commit message.
>>>  - Optimize the description of the hw_pattern file.
>>>  - Simplify some logics.
>>>
>>> Changes from v5:
>>>  - Add one 'hw_pattern' file for hardware patterns.
>>>
>>> Changes from v4:
>>>  - Change the repeat file to return the originally written number.
>>>  - Improve comments.
>>>  - Fix some build warnings.
>>>
>>> Changes from v3:
>>>  - Reset pattern number to 0 if user provides incorrect pattern string.
>>>  - Support one pattern.
>>>
>>> Changes from v2:
>>>  - Remove hardware_pattern boolen.
>>>  - Chnage the pattern string format.
>>>
>>> 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    |  76 ++++
>>>  drivers/leds/trigger/Kconfig                       |   7 +
>>>  drivers/leds/trigger/Makefile                      |   1 +
>>>  drivers/leds/trigger/ledtrig-pattern.c             | 431 +++++++++++++++++++++
>>>  include/linux/leds.h                               |  15 +
>>>  5 files changed, 530 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..22d7af7
>>> --- /dev/null
>>> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>>> @@ -0,0 +1,76 @@
>>> +What:                /sys/class/leds/<led>/pattern
>>> +Date:                September 2018
>>> +KernelVersion:       4.20
>>> +Description:
>>> +             Specify a software pattern for the LED, that supports altering
>>> +             the brightness for the specified duration with one software
>>> +             timer. It can do gradual dimming and constant brightness.
>>> +
>>> +             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.
>>> +
>>> +             1. When doing gradual dimming, the led brightness will be updated
>>> +             every 50 milliseconds, so the duration of each step should not
>>> +             less than 50 milliseconds.
>>
>> I'd like to avoid this constraint. Lowest supported delta_t should be 1.
>>
>> We should only prevent entering dimming mode if current delta_t
>> is lower than UPDATE_INTERVAL.
> 
> I do not think so. If the pattern format is used for dimming and the
> delta_t is lower than UPDATE_INTERVAL, we should return errors. Since
> in this case, we can not change to constant mode.

I'll play with the code at weekend and will let you know my findings.

Best regards,
Jacek Anaszewski


> Like you mentioned:
> 
> echo "10 49 20 49" > pattern
> 
> We can not enter dimming, meanwhile the pattern format is not used for
> constant brightness, so should return errors for the invalid pattern
> values.
> 
>> I also propose to make the dimming interval configurable via sysfs
>> dimming_interval file.
> 
> So the dimming_interva range is [1, 50] milliseconds?
> 
> I am fine with this. Pavel, do you also agree with adding one new file
> to set the dimming interval or keep it as simple now?
> 
>>
>>> The gradual dimming format of the
>>> +             software pattern values should be:
>>> +             "brightness_1 duration_1 brightness_2 duration_2 brightness_3
>>> +             duration_3 ...". For example:
>>> +
>>> +             echo 0 1000 255 2000 > pattern
>>> +
>>> +             It will make the LED go gradually from zero-intensity to max (255)
>>> +             intensity in 1000 milliseconds, then back to zero intensity in 2000
>>> +             milliseconds:
>>> +
>>> +             LED brightness
>>> +                 ^
>>> +             255-|       / \            / \            /
>>> +                 |      /    \         /    \         /
>>> +                 |     /       \      /       \      /
>>> +                 |    /          \   /          \   /
>>> +               0-|   /             \/             \/
>>> +                 +---0----1----2----3----4----5----6------------> time (s)
>>> +
>>> +             2. To make the LED go instantly from one brigntess value to another,
>>> +             we should use use zero-time lengths. So the format should be:
>>> +             "brightness_1 duration_1 brightness_1 0 brightness_2 duration_2
>>> +             brightness_2 0 ...". For example:
>>> +
>>> +             echo 0 1000 0 0 255 2000 255 0 > pattern
>>> +
>>> +             It will make the LED stay off for one second, then stay at max brightness
>>> +             for two seconds:
>>> +
>>> +             LED brightness
>>> +                 ^
>>> +             255-|        +---------+    +---------+
>>> +                 |        |         |    |         |
>>> +                 |        |         |    |         |
>>> +                 |        |         |    |         |
>>> +               0-|   -----+         +----+         +----
>>> +                 +---0----1----2----3----4----5----6------------> time (s)
>>> +
>>> +What:                /sys/class/leds/<led>/hw_pattern
>>> +Date:                September 2018
>>> +KernelVersion:       4.20
>>> +Description:
>>> +             Specify a hardware pattern for the LED, for LED hardware that
>>> +             supports autonomously controlling brightness over time, according
>>> +             to some preprogrammed hardware patterns.
>>> +
>>> +             Since different LED hardware can have different semantics of
>>> +             hardware patterns, each driver is expected to provide its own
>>> +             description for the hardware patterns in their ABI documentation
>>> +             file.
>>> +
>>> +What:                /sys/class/leds/<led>/repeat
>>> +Date:                September 2018
>>> +KernelVersion:       4.20
>>> +Description:
>>> +             Specify a pattern repeat number. -1 means repeat indefinitely,
>>> +             other negative numbers and number 0 are invalid.
>>> +
>>> +             This file will always return the originally written repeat
>>> +             number.
>>> 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..92a0fd0
>>> --- /dev/null
>>> +++ b/drivers/leds/trigger/ledtrig-pattern.c
>>> @@ -0,0 +1,431 @@
>>> +// 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
>>> +/*
>>> + * When doing gradual dimming, the led brightness will be updated
>>> + * every 50 milliseconds.
>>> + */
>>> +#define UPDATE_INTERVAL              50
>>> +
>>> +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;
>>> +     int repeat;
>>> +     int last_repeat;
>>> +     int delta_t;
>>> +     bool is_indefinite;
>>> +     bool is_hw_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++;
>>> +
>>> +     data->delta_t = 0;
>>> +}
>>> +
>>> +static int pattern_trig_compute_brightness(struct pattern_trig_data *data)
>>> +{
>>> +     int step_brightness;
>>> +
>>> +     if (data->delta_t == 0)
>>> +             return data->curr->brightness;
>>> +
>>> +     step_brightness = abs(data->next->brightness - data->curr->brightness);
>>> +     step_brightness = data->delta_t * step_brightness / data->curr->delta_t;
>>> +
>>> +     if (data->next->brightness > data->curr->brightness)
>>> +             return data->curr->brightness + step_brightness;
>>> +     else
>>> +             return data->curr->brightness - step_brightness;
>>> +}
>>> +
>>> +static void pattern_trig_timer_function(struct timer_list *t)
>>> +{
>>> +     struct pattern_trig_data *data = from_timer(data, t, timer);
>>> +
>>> +     mutex_lock(&data->lock);
>>> +
>>> +     for (; ;) {
>>
>> This whitespace between semicolons looks odd. Please remove it.
> 
> Sure.
> 
>>
>>> +             if (!data->is_indefinite && !data->repeat)
>>> +                     break;
>>> +
>>> +             if (data->curr->brightness == data->next->brightness) {
>>> +                     /* Constant brightness */
>>> +                     led_set_brightness(data->led_cdev,
>>> +                                        data->curr->brightness);
>>> +                     mod_timer(&data->timer,
>>> +                               jiffies + msecs_to_jiffies(data->curr->delta_t));
>>> +
>>> +                     /* Skip the step with zero duration */
>>> +                     pattern_trig_update_patterns(data);
>>> +                     /* Select next step */
>>> +                     pattern_trig_update_patterns(data);
>>> +                     break;
>>> +             } else {
>>> +                     /* Gradual dimming */
>>> +
>>> +                     /*
>>> +                      * If the accumulation time is larger than current
>>> +                      * step duration, we should go next one and re-check
>>> +                      * if we repeated done.
>>> +                      */
>>> +                     if (data->delta_t > data->curr->delta_t) {
>>> +                             pattern_trig_update_patterns(data);
>>> +                             continue;
>>> +                     }
>>> +
>>> +                     led_set_brightness(data->led_cdev,
>>> +                                        pattern_trig_compute_brightness(data));
>>> +                     mod_timer(&data->timer,
>>> +                               jiffies + msecs_to_jiffies(UPDATE_INTERVAL));
>>> +                     /* Accumulate the gradual dimming time */
>>> +                     data->delta_t += UPDATE_INTERVAL;
>>> +                     break;
>>> +             }
>>
>> Why two "break" statements instead of one here?
> 
> Yes, can remove one. Sorry for the quick version patch set without
> much self-checking in the night. Thanks for your comments.
>