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Message-ID: <7051613e-f2db-260f-85d7-d40278fd11cb@gmail.com>
Date: Thu, 4 Oct 2018 22:00:49 +0200
From: Jacek Anaszewski <jacek.anaszewski@...il.com>
To: Baolin Wang <baolin.wang@...aro.org>
Cc: Pavel Machek <pavel@....cz>, rteysseyre@...il.com,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Mark Brown <broonie@...nel.org>,
Linux LED Subsystem <linux-leds@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v14 1/2] leds: core: Introduce LED pattern trigger
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@...il.com> 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@...il.com>
>>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>>> ---
>>> 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.
>
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