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SubjectRe: [PATCH v7 1/2] leds: core: Introduce LED pattern trigger
Hi Jacek,

On 4 September 2018 at 02:58, Jacek Anaszewski
<jacek.anaszewski@gmail.com> wrote:
> Hi Baolin,
>
> Thank you for the update.
>
> Please find my remarks below.
>
> On 08/31/2018 09:52 AM, 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@gmail.com>
>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>> ---
>> 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 | 44 +++
>> drivers/leds/trigger/Kconfig | 7 +
>> drivers/leds/trigger/Makefile | 1 +
>> drivers/leds/trigger/ledtrig-pattern.c | 337 ++++++++++++++++++++
>> include/linux/leds.h | 16 +
>> 5 files changed, 405 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..f4749d1
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>> @@ -0,0 +1,44 @@
>> +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.
>> +
>> + 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 software pattern values should be:
>> + "brightness_1 duration_1 brightness_2 duration_2 brightness_3
>> + duration_3 ...".
>> +
>> +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 as below.
>
> And I would cut this description here.
>
>> + For Spreadtrum SC27XX LED controller, it only supports 4 hardware
>> + patterns to configure the low time, rise time, high time and fall
>> + time for the breathing mode, and each stage duration unit is 125ms.
>> + So the format of the hardware pattern values should be:
>> + "brightness_1 duration_1 brightness_2 duration_2 brightness_3
>> + duration_3 brightness_4 duration_4".
>
> This part should go to the separate ABI documentation file, related to
> the driver for Spreadtrum SC27XX.

Ah, sure. Will update in v8. Thanks.

>
>> +
>> +What: /sys/class/leds/<led>/repeat
>> +Date: September 2018
>> +KernelVersion: 4.20
>> +Description:
>> + Specify a pattern repeat number. 0 means repeat indefinitely.
>> +
>> + 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..0179191
>> --- /dev/null
>> +++ b/drivers/leds/trigger/ledtrig-pattern.c
>> @@ -0,0 +1,337 @@
>> +// 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
>> +
>> +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;
>> + u32 last_repeat;
>> + 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++;
>> +}
>> +
>> +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 led_classdev *led_cdev)
>> +{
>> + struct pattern_trig_data *data = led_cdev->trigger_data;
>> +
>> + if (!data->npatterns)
>> + return 0;
>> +
>> + if (data->is_hw_pattern) {
>> + return led_cdev->pattern_set(led_cdev, data->patterns,
>> + data->npatterns, data->repeat);
>> + }
>
> I have doubts here if it is a good idea to enforce array of tuples
> as a generic interface for all hw_patterns. It may not fit well for
> every hw pattern engine. It seems that the only feasible solution will
> be allowing drivers to come up with their own interfaces, i.e. the
> approach you proposed at first for your driver. It seems that the
> ledtrig-pattern with software pattern mechanism will be just
> a nice side effect of this series :-)
>
> Unless someone will propose a better solution.
>
> We need a broader consensus here. I'd like to hear Pavel's opinion,
> since he's been always in favor of common pattern interface, and
> inspired this work.
>
> Pavel?
>
> Best regards,
> Jacek Anaszewski



--
Baolin Wang
Best Regards

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