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Message-ID: <54d4debc-470a-86f6-e43c-f51f1c7913e0@gmail.com>
Date: Tue, 24 Sep 2019 23:30:08 +0200
From: Jacek Anaszewski <jacek.anaszewski@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Akinobu Mita <akinobu.mita@...il.com>, linux-leds@...r.kernel.org,
linux-kernel@...r.kernel.org,
"Rafael J. Wysocki" <rafael@...nel.org>,
Pavel Machek <pavel@....cz>, Dan Murphy <dmurphy@...com>
Subject: Re: [PATCH v2 1/1] leds: remove PAGE_SIZE limit of
/sys/class/leds/<led>/trigger
Hi Greg,
Akinobu seems to have addressed all issues that have been
raised regarding this patch. I'd be happy to have your ack before
applying it.
Best regards,
Jacek Anaszewski
On 9/13/19 5:03 PM, Akinobu Mita wrote:
> Reading /sys/class/leds/<led>/trigger returns all available LED triggers.
> However, the size of this file is limited to PAGE_SIZE because of the
> limitation for sysfs attribute.
>
> Enabling LED CPU trigger on systems with thousands of CPUs easily hits
> PAGE_SIZE limit, and makes it impossible to see all available LED triggers
> and which trigger is currently activated.
>
> We work around it here by converting /sys/class/leds/<led>/trigger to
> binary attribute, which is not limited by length. This is _not_ good
> design, do not copy it.
>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Jacek Anaszewski <jacek.anaszewski@...il.com>
> Cc: Pavel Machek <pavel@....cz>
> Cc: Dan Murphy <dmurphy@...com>
> Acked-by: Pavel Machek <pavel@....cz>
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
> ---
> drivers/leds/led-class.c | 8 ++--
> drivers/leds/led-triggers.c | 90 ++++++++++++++++++++++++++++++++++-----------
> drivers/leds/leds.h | 6 +++
> include/linux/leds.h | 5 ---
> 4 files changed, 79 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 4793e77..8b5a1d1 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -73,13 +73,13 @@ static ssize_t max_brightness_show(struct device *dev,
> static DEVICE_ATTR_RO(max_brightness);
>
> #ifdef CONFIG_LEDS_TRIGGERS
> -static DEVICE_ATTR(trigger, 0644, led_trigger_show, led_trigger_store);
> -static struct attribute *led_trigger_attrs[] = {
> - &dev_attr_trigger.attr,
> +static BIN_ATTR(trigger, 0644, led_trigger_read, led_trigger_write, 0);
> +static struct bin_attribute *led_trigger_bin_attrs[] = {
> + &bin_attr_trigger,
> NULL,
> };
> static const struct attribute_group led_trigger_group = {
> - .attrs = led_trigger_attrs,
> + .bin_attrs = led_trigger_bin_attrs,
> };
> #endif
>
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 8d11a5e..ed5a311 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -16,6 +16,7 @@
> #include <linux/rwsem.h>
> #include <linux/leds.h>
> #include <linux/slab.h>
> +#include <linux/mm.h>
> #include "leds.h"
>
> /*
> @@ -26,9 +27,11 @@ LIST_HEAD(trigger_list);
>
> /* Used by LED Class */
>
> -ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
> - const char *buf, size_t count)
> +ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *bin_attr, char *buf,
> + loff_t pos, size_t count)
> {
> + struct device *dev = kobj_to_dev(kobj);
> struct led_classdev *led_cdev = dev_get_drvdata(dev);
> struct led_trigger *trig;
> int ret = count;
> @@ -64,39 +67,84 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
> mutex_unlock(&led_cdev->led_access);
> return ret;
> }
> -EXPORT_SYMBOL_GPL(led_trigger_store);
> +EXPORT_SYMBOL_GPL(led_trigger_write);
>
> -ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr,
> - char *buf)
> +__printf(4, 5)
> +static int led_trigger_snprintf(char *buf, size_t size, bool query,
> + const char *fmt, ...)
> +{
> + va_list args;
> + int i;
> +
> + va_start(args, fmt);
> + if (query)
> + i = vsnprintf(NULL, 0, fmt, args);
> + else
> + i = vscnprintf(buf, size, fmt, args);
> + va_end(args);
> +
> + return i;
> +}
> +
> +static int led_trigger_format(char *buf, size_t size, bool query,
> + struct led_classdev *led_cdev)
> {
> - struct led_classdev *led_cdev = dev_get_drvdata(dev);
> struct led_trigger *trig;
> - int len = 0;
> + int len = led_trigger_snprintf(buf, size, query, "%s",
> + led_cdev->trigger ? "none" : "[none]");
> +
> + list_for_each_entry(trig, &trigger_list, next_trig) {
> + bool hit = led_cdev->trigger &&
> + !strcmp(led_cdev->trigger->name, trig->name);
> +
> + len += led_trigger_snprintf(buf + len, size - len, query,
> + " %s%s%s", hit ? "[" : "",
> + trig->name, hit ? "]" : "");
> + }
> +
> + len += led_trigger_snprintf(buf + len, size - len, query, "\n");
> +
> + return len;
> +}
> +
> +/*
> + * It was stupid to create 10000 cpu triggers, but we are stuck with it now.
> + * Don't make that mistake again. We work around it here by creating binary
> + * attribute, which is not limited by length. This is _not_ good design, do not
> + * copy it.
> + */
> +ssize_t led_trigger_read(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *attr, char *buf,
> + loff_t pos, size_t count)
> +{
> + struct device *dev = kobj_to_dev(kobj);
> + struct led_classdev *led_cdev = dev_get_drvdata(dev);
> + void *data;
> + int len;
>
> down_read(&triggers_list_lock);
> down_read(&led_cdev->trigger_lock);
>
> - if (!led_cdev->trigger)
> - len += scnprintf(buf+len, PAGE_SIZE - len, "[none] ");
> + len = led_trigger_format(NULL, 0, true, led_cdev);
> + data = kvmalloc(len + 1, GFP_KERNEL);
> + if (data)
> + len = led_trigger_format(data, len + 1, false, led_cdev);
> else
> - len += scnprintf(buf+len, PAGE_SIZE - len, "none ");
> + len = -ENOMEM;
>
> - list_for_each_entry(trig, &trigger_list, next_trig) {
> - if (led_cdev->trigger && !strcmp(led_cdev->trigger->name,
> - trig->name))
> - len += scnprintf(buf+len, PAGE_SIZE - len, "[%s] ",
> - trig->name);
> - else
> - len += scnprintf(buf+len, PAGE_SIZE - len, "%s ",
> - trig->name);
> - }
> up_read(&led_cdev->trigger_lock);
> up_read(&triggers_list_lock);
>
> - len += scnprintf(len+buf, PAGE_SIZE - len, "\n");
> + if (len < 0)
> + return len;
> +
> + len = memory_read_from_buffer(buf, count, &pos, data, len);
> +
> + kvfree(data);
> +
> return len;
> }
> -EXPORT_SYMBOL_GPL(led_trigger_show);
> +EXPORT_SYMBOL_GPL(led_trigger_read);
>
> /* Caller must ensure led_cdev->trigger_lock held */
> int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
> diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
> index 47b2294..a0ee33c 100644
> --- a/drivers/leds/leds.h
> +++ b/drivers/leds/leds.h
> @@ -23,6 +23,12 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev,
> enum led_brightness value);
> void led_set_brightness_nosleep(struct led_classdev *led_cdev,
> enum led_brightness value);
> +ssize_t led_trigger_read(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *attr, char *buf,
> + loff_t pos, size_t count);
> +ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *bin_attr, char *buf,
> + loff_t pos, size_t count);
>
> extern struct rw_semaphore leds_list_lock;
> extern struct list_head leds_list;
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index fd2eb7c..33ae825 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -290,11 +290,6 @@ struct led_trigger {
> #define led_trigger_get_led(dev) ((struct led_classdev *)dev_get_drvdata((dev)))
> #define led_trigger_get_drvdata(dev) (led_get_trigger_data(led_trigger_get_led(dev)))
>
> -ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
> - const char *buf, size_t count);
> -ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr,
> - char *buf);
> -
> /* Registration functions for complex triggers */
> extern int led_trigger_register(struct led_trigger *trigger);
> extern void led_trigger_unregister(struct led_trigger *trigger);
>
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