linux-kernel - Re: [PATCH v3 1/1] leds: remove PAGE_SIZE limit of /sys/class/leds/<led>/trigger

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Message-ID: <20190929144654.GB2011467@kroah.com>
Date:   Sun, 29 Sep 2019 16:46:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Akinobu Mita <akinobu.mita@...il.com>
Cc:     linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>, Dan Murphy <dmurphy@...com>
Subject: Re: [PATCH v3 1/1] leds: remove PAGE_SIZE limit of
 /sys/class/leds/<led>/trigger

On Sun, Sep 29, 2019 at 11:18:49PM +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.
> 
> 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>
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>