Re: [PATCH 1/5] leds: remove PAGE_SIZE limit of /sys/class/leds/<led>/trigger

From: Akinobu Mita <akinobu.mita@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-leds@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Jacek Anaszewski <jacek.anaszewski@gmail.com>,
	Pavel Machek <pavel@ucw.cz>, Dan Murphy <dmurphy@ti.com>
Subject: Re: [PATCH 1/5] leds: remove PAGE_SIZE limit of /sys/class/leds/<led>/trigger
Date: Thu, 12 Sep 2019 00:25:28 +0900	[thread overview]
Message-ID: <CAC5umyhZ_-Gdh7+EzNoHPs2zki2-dK1xBv5xpE5zwZPt_jvNEA@mail.gmail.com> (raw)
In-Reply-To: <20190908131034.GD9466@kroah.com>

2019年9月8日(日) 22:10 Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
>
> On Sun, Sep 08, 2019 at 09:41:08PM +0900, 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.
> >
> > This converts /sys/class/leds/<led>/trigger to bin attribute and removes
> > the PAGE_SIZE limitation.
> >
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> > Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: Dan Murphy <dmurphy@ti.com>
> > Acked-by: Pavel Machek <pavel@ucw.cz>
> > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.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);
>
> BIN_ATTR_RW()?

We can use BIN_ATTR_RW() by renaming led_trigger_{read,write}() to
trigger_{read,write}().  But led_trigger_{read,write}() are not static
functions.  These are defined as export symbols for led-class module.

So trigger_{read,write}() will be too generic symbol names, won't they?