linux-kernel - Re: [PATCH] leds: remove PAGE_SIZE limit of /sys/class/leds/<led>/trigger

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Date:   Thu, 12 Sep 2019 19:15:53 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Akinobu Mita <akinobu.mita@...il.com>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, Dan Murphy <dmurphy@...com>
Subject: Re: [PATCH] leds: remove PAGE_SIZE limit of
 /sys/class/leds/<led>/trigger

Hi Akinobu,

Please bump patch version each time you send an update
of the patch with the same subject.

Best regards,
Jacek Anaszewski

On 9/12/19 4:39 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.