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Message-ID: <CAMz4kuKpeciThaXNN6zww0v1yxuUQkOPdsNuPj=-zw_kWUwKuw@mail.gmail.com>
Date: Tue, 31 Jul 2018 14:52:46 +0800
From: Baolin Wang <baolin.wang@...aro.org>
To: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Jacek Anaszewski <jacek.anaszewski@...il.com>,
Pavel Machek <pavel@....cz>,
David Lechner <david@...hnology.com>,
Mark Brown <broonie@...nel.org>,
Linux LED Subsystem <linux-leds@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] leds: core: Introduce LED pattern trigger
On 31 July 2018 at 14:22, Baolin Wang <baolin.wang@...aro.org> wrote:
> Hi Bjorn,
>
> On 31 July 2018 at 11:54, Bjorn Andersson <bjorn.andersson@...aro.org> wrote:
>> On Mon 30 Jul 05:29 PDT 2018, 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@...il.com>
>>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>>> ---
>>> .../ABI/testing/sysfs-class-led-trigger-pattern | 21 ++
>>> drivers/leds/trigger/Kconfig | 10 +
>>> drivers/leds/trigger/Makefile | 1 +
>>> drivers/leds/trigger/ledtrig-pattern.c | 349 ++++++++++++++++++++
>>> include/linux/leds.h | 19 ++
>>> 5 files changed, 400 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..c52da34
>>> --- /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.
>>
>> If 0 means infinity, does 1 mean "repeat 1 time"? If so how would I
>
> Right.
>
>> specify that I want the pattern to run one time (i.e. 0 repetitions).
>
> If you set repeat to 1 to make the driver clear the is_indefinite
> flag. So when the repeat number decreases to 0, it will stop.
>
>>
>>> diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
>>> index a2559b4..a03afcd 100644
>>> --- a/drivers/leds/trigger/Kconfig
>>> +++ b/drivers/leds/trigger/Kconfig
>>> @@ -125,6 +125,16 @@ config LEDS_TRIGGER_CAMERA
>>> This enables direct flash/torch on/off by the driver, kernel space.
>>> If unsure, say Y.
>>>
>>> +config LEDS_TRIGGER_PATTERN
>>> + tristate "LED Pattern Trigger"
>>> + depends on LEDS_TRIGGERS
>>> + help
>>> + This allows LEDs blinking with an arbitrary pattern. Can be useful
>>> + on embedded systems with no screen to give out a status code to
>>> + a human.
>>
>> While the pattern mechanism could be used to communicate some message
>> the use cases we've seen so far is all about enabling hardware to pulse
>> LEDs instead of blinking them...
>
> Right. I will improve the message here.
>
>>
>>> +
>>> + If unsure, say N
>>> +
>>> config LEDS_TRIGGER_PANIC
>>> bool "LED Panic Trigger"
>>> depends on LEDS_TRIGGERS
>>> diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
>>> index f3cfe19..c5d180e 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..b709aa1
>>> --- /dev/null
>>> +++ b/drivers/leds/trigger/ledtrig-pattern.c
>>> @@ -0,0 +1,349 @@
>>> +// 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.
>>
>> Might be a coincidence, but parts of this patch looks pretty close to
>> mine...
>>
>>> + */
>>> +
>>> +#include <linux/kernel.h>
>>> +#include <linux/leds.h>
>>> +#include <linux/module.h>
>>> +#include <linux/mutex.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/timer.h>
>>> +
>>> +/*
>>> + * The "pattern" attribute contains at most PAGE_SIZE characters. Each line
>>> + * in this attribute is at least 4 characters long (a 1-digit number for the
>>> + * led brighntess, a space, a 1-digit number for the time, a semi-colon).
>>> + * Therefore, there is at most PAGE_SIZE/4 patterns.
>>> + */
>>
>> The brightness is a number between 0 and LED_FULL (or max_brightness)
>> and delta_t is measured in ms. So neither of these are likely to be a
>> single digit very often.
>
> OK. Will fix these comments.
>
>>
>>> +#define MAX_PATTERNS (PAGE_SIZE / 4)
>>> +#define PATTERN_SEPARATOR ","
>>> +
>>> +struct pattern_trig_data {
>>> + struct led_classdev *led_cdev;
>>> + struct led_pattern *patterns;
>>> + struct led_pattern *curr;
>>> + struct led_pattern *next;
>>> + struct mutex lock;
>>> + u32 npatterns;
>>> + u32 repeat;
>>> + bool is_indefinite;
>>> + struct timer_list timer;
>>> +};
>>> +
>>> +static void pattern_trig_update_patterns(struct pattern_trig_data *data)
>>
>> I think you should just inline this logic into
>> pattern_trig_timer_function() to make it obvious that this is only
>> invoked from the timer function.
>>
>> And if you do this you can decrement data->repeat unconditionally after
>> the check for !is_indefinite && repeat == 0.
>
> OK.
We can not remove the condition, since we still should make sure the
data->curr points the fist pattern again.
>
>>
>>> +{
>>> + 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++;
>>
>> How about replacing this conditional with:
>>
>> data->next = (data->next + 1) % data->npatterns;
>
> Good suggestion. Will do in next version.
Re-think about this. The data->next is one pointer which points next
pattern not one index. So I think I can not do like this.
>
>>
>>> +}
>>> +
>>> +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 (led_cdev->pattern_clear)
>>> + led_cdev->pattern_clear(led_cdev);
>>> +
>>> + if (led_cdev->pattern_set) {
>>
>> In my proposal setting an empty pattern would invoke pattern_clear() and
>> setting a pattern would invoke pattern_set(), this allows the driver to
>> fail the pattern_set() without clearing the old pattern.
>
> Pavel wanted "echo none > trigger" to clear the pattern. So I am fine
> remove the 'pattern_clear' operation in this function.
>
>>
>>> + return led_cdev->pattern_set(led_cdev, data->patterns,
>>> + data->npatterns, data->repeat);
>>
>> repeat is communicated to the driver, but is_indefinite is not. At least
>> in my driver the latter
Sorry I missed this comments. I think the repeat number can be easily
converted to decide if is indefinite in your driver.
>>
>>> + }
>>
>> I think it would be useful to put the rest in an else statement, to
>> clarify that the patterns is either implemented by the driver or by the
>> software timer. It might also make sense to group the check for
>> pattern_clear() and pattern_set(), as it wouldn't make sense for the
>> driver to implement only one of these.
>
> But checkpatch will complain the 'else' statement is redundant, maybe
> add some comments here to make things clear?
>
>>
>>> +
>>> + 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;
>>> + int err;
>>> + u32 repeat;
>>> +
>>> + mutex_lock(&data->lock);
>>> +
>>> + if (led_cdev->pattern_get) {
>>> + err = led_cdev->pattern_get(led_cdev, data->patterns,
>>> + &data->npatterns, &data->repeat);
>>
>> I don't see why "repeat" would have changed since you told the driver,
>> so data->repeat should have the right value already.
>
> Some drivers don't care about the repeat, and it will always repeat
> indefinitely. So no matter what values set from userspace, driver can
> set it to 0.
>
>>
>>> + if (err) {
>>> + mutex_unlock(&data->lock);
>>> + return err;
>>> + }
>>> + }
>>> +
>>> + 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;
>>> +
>>> + del_timer_sync(&data->timer);
>>> +
>>> + mutex_lock(&data->lock);
>>> + data->repeat = res;
>>> +
>>> + /* 0 means repeat indefinitely */
>>
>> I think that it would be better to specify indefinite by writing e.g.
>> "Inf" to the repeat.
>>
>> Also note that it's possible that there might be hardware restrictions
>> that only allows specific combinations of these; e.g. the Qualcomm
>> hardware can only do no-repeat or repeat-forever.
>
> Can you set repeat to 1 to represent no-repeat and set to 0 to
> represent repeat-forever?
>
>>
>>> + if (!data->repeat)
>>> + data->is_indefinite = true;
>>> + else
>>> + data->is_indefinite = false;
>>> +
>>> + err = pattern_trig_start_pattern(data, led_cdev);
>>> + if (err) {
>>> + mutex_unlock(&data->lock);
>>> + return err;
>>> + }
>>> +
>>> + mutex_unlock(&data->lock);
>>> + return 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 err, i;
>>> +
>>> + mutex_lock(&data->lock);
>>> +
>>> + if (led_cdev->pattern_get) {
>>> + err = led_cdev->pattern_get(led_cdev, data->patterns,
>>> + &data->npatterns, &data->repeat);
>>> + if (err) {
>>> + mutex_unlock(&data->lock);
>>> + return err;
>>> + }
>>> + }
>>
>> Rather than sometimes calling pattern_get() here, how about defining
>> that pattern_set() should update data->patterns before returning and
>> just rely on data->patterns being right.
>>
>> (The reason for the pattern not being the same as passed in store would
>> be to allow the driver to adjust the parameters to the match the
>> hardware requirements and present this to the user)
>
> Hmmm, so we can remove the 'pattern_get' interface and always trust
> data->patterns.
>
>>
>>> +
>>> + if (!data->npatterns) {
>>> + mutex_unlock(&data->lock);
>>> + return -EINVAL;
>>> + }
>>
>> Rather than failing I think you should return the empty string if the
>> pattern is empty.
>
> Sure.
>
>>
>>> +
>>> + 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';
>>> + buf[count] = '\0';
>>> +
>>> + mutex_unlock(&data->lock);
>>> + return count + 1;
>>
>> As you're returning a string I think you should return the number of
>> chars in the string, not including the '\0'.
>
> Sure.
>
>>
>>> +}
>>> +
>>> +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 err, cr, ccount, tcr = 0;
>>> +
>>> + del_timer_sync(&data->timer);
>>> +
>>> + mutex_lock(&data->lock);
>>> +
>>> + for (data->npatterns = 0; data->npatterns < MAX_PATTERNS;
>>> + data->npatterns++) {
>>> + /* Characters read on one conversion */
>>> + cr = 0;
>>> + /* Number of successful conversions */
>>> + ccount = sscanf(buf + tcr, "%d %d " PATTERN_SEPARATOR "%n",
>>> + &data->patterns[data->npatterns].brightness,
>>> + &data->patterns[data->npatterns].delta_t, &cr);
>>
>> I'm not fond of the use of sscanf() here, but at least you should make
>> sure that tcr doesn't go past PAGE_SIZE.
>
> Yes.
>
>>
>>> +
>>> + /* Total characters read */
>>> + tcr += cr;
>>> + if (cr)
>>> + continue;
>>
>> This loop is non-intuitive...
>>
>> You loop while npatterns is less than MAX_PATTERNS and the first half
>> will loop if sscanf() matched the pattern otherwise you'll return from
>> withing the loop.
>
> OK. Will improve this loop here in next version.
>
>>
>>> +
>>> + /* Invalid syntax or end of pattern */
>>> + if (ccount == 2)
>>
>> I guess you'll get here if you match the two %d, but not the
>> PATTERN_SEPARATOR? Wouldn't it be useful to fail here if ccount is !2.
>
> Yes. OK, I will fail it if ccount is !2.
>
>>
>>> + data->npatterns++;
>>> +
>>> + err = pattern_trig_start_pattern(data, led_cdev);
>>> + if (err) {
>>> + mutex_unlock(&data->lock);
>>> + return err;
>>> + }
>>> +
>>> + mutex_unlock(&data->lock);
>>> + return count;
>>> + }
>>> +
>>> + /* Shouldn't reach that */
>>
>> This means that you failed to set the pattern, so you probably shouldn't
>> return count - but rather -EINVAL or something.
>
> Right.
>
>>
>>> + WARN(1, "MAX_NSTEP too small. Please report\n");
>>> + mutex_unlock(&data->lock);
>>> + return count;
>>> +}
>>> +
>>> +static DEVICE_ATTR(pattern, 0644, pattern_trig_show_pattern,
>>> + pattern_trig_store_pattern);
>>> +
>>> +static int pattern_trig_create_sysfs_files(struct device *dev)
>>> +{
>>> + int err;
>>> +
>>> + err = device_create_file(dev, &dev_attr_repeat);
>>> + if (err)
>>> + return err;
>>> +
>>> + err = device_create_file(dev, &dev_attr_pattern);
>>> + if (err)
>>> + device_remove_file(dev, &dev_attr_repeat);
>>> +
>>> + return err;
>>> +}
>>> +
>>> +static void pattern_trig_remove_sysfs_files(struct device *dev)
>>> +{
>>> + device_remove_file(dev, &dev_attr_pattern);
>>> + device_remove_file(dev, &dev_attr_repeat);
>>> +}
>>> +
>>> +static int pattern_trig_initialize_data(struct pattern_trig_data *data)
>>
>> These two functions would be better to just inline, but...
>
> Will re-consider these two functions.
>
>>
>>> +{
>>> + data->patterns = kcalloc(MAX_PATTERNS, sizeof(struct led_pattern),
>>> + GFP_KERNEL);
>>
>> ...as this always allocate 1024 entries of led_pattern associated with
>> the pattern_trig_data you should just add 1024 entries of led_pattern to
>> the pattern_trig_data struct.
>
> Right.
>
>>
>>> + if (!data->patterns)
>>> + return -ENOMEM;
>>> +
>>> + data->is_indefinite = true;
>>> + mutex_init(&data->lock);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static void pattern_trig_clear_data(struct pattern_trig_data *data)
>>> +{
>>> + kfree(data->patterns);
>>> +}
>>> +
>>> +static void pattern_trig_activate(struct led_classdev *led_cdev)
>>> +{
>>> + struct pattern_trig_data *data;
>>> + int err;
>>> +
>>> + data = kzalloc(sizeof(*data), GFP_KERNEL);
>>> + if (!data)
>>> + return;
>>> +
>>> + err = pattern_trig_initialize_data(data);
>>> + if (err) {
>>> + kfree(data);
>>> + return;
>>> + }
>>> +
>>> + err = pattern_trig_create_sysfs_files(led_cdev->dev);
>>> + if (err) {
>>> + pattern_trig_clear_data(data);
>>> + kfree(data);
>>> + return;
>>> + }
>>> +
>>> + data->led_cdev = led_cdev;
>>> + led_cdev->trigger_data = data;
>>> + timer_setup(&data->timer, pattern_trig_timer_function, 0);
>>> + led_cdev->activated = true;
>>> +}
>>> +
>>> +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 (led_cdev->pattern_clear)
>>> + led_cdev->pattern_clear(led_cdev);
>>> +
>>> + del_timer_sync(&data->timer);
>>
>> This should only happen when not having using the driver based
>> mechanism, so put this in an else to clarify this.
>
> OK.
>
>>
>>> + pattern_trig_remove_sysfs_files(led_cdev->dev);
>>
>> Inline this and one doesn't have to jump around to figure out what's
>> going on.
>
> Sure. Thanks for your useful comments.
>
>>
>>> + led_set_brightness(led_cdev, LED_OFF);
>>> + pattern_trig_clear_data(data);
>>> + kfree(data);
>>> + led_cdev->trigger_data = NULL;
>>> + led_cdev->activated = false;
>>> +}
>>> +
>>> +static struct led_trigger pattern_led_trigger = {
>>> + .name = "pattern",
>>> + .activate = pattern_trig_activate,
>>> + .deactivate = pattern_trig_deactivate,
>>> +};
>>> +
>>> +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@...il.com");
>>> +MODULE_AUTHOR("Baolin Wang <baolin.wang@...aro.org");
>>> +MODULE_DESCRIPTION("LED Pattern trigger");
>>> +MODULE_LICENSE("GPL v2");
>>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>>> index b7e8255..bea02f0 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 +89,14 @@ 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_get)(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;
>>>
>>> @@ -446,4 +455,14 @@ 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 */
>>> --
>>> 1.7.9.5
>>>
>
>
>
> --
> Baolin Wang
> Best Regards
--
Baolin Wang
Best Regards
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