linux-kernel - Re: outdated documentation for lp5523 LED driver?

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Message-ID: <20160715092657.GA25380@amd>
Date:	Fri, 15 Jul 2016 11:26:57 +0200
From:	Pavel Machek <pavel@....cz>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	sre@...nel.org, kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
	aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
	patrikbachan@...il.com, serge@...lyn.com, samu.p.onkalo@...ia.com,
	milo.kim@...com, toshik@...omium.org, j.anaszewski@...sung.com,
	cooloney@...il.com
Subject: Re: outdated documentation for lp5523 LED driver?

On Fri 2016-07-15 11:01:10, Pali Rohár wrote:
> On Friday 15 July 2016 10:54:25 Pavel Machek wrote:
> > On Fri 2016-07-15 09:40:52, Pali Rohár wrote:
> > > On Friday 15 July 2016 09:32:14 Pavel Machek wrote:
> > > > Hi!
> > > > 
> > > > Documentation says that load/leds are only visible in the load mode,
> > > > but that does not seem to be true (kernel 4.4.0 on N900).
> > > > 
> > > > # 1) Legacy interface - enginex_mode, enginex_load and enginex_leds
> > > > #  Control interface for the engines:
> > > > #    x is 1 .. 3
> > > > #      enginex_mode : disabled, load, run
> > > > #      enginex_load : microcode load (visible only in load mode)
> > > > #      enginex_leds : led mux control (visible only in load mode)
> > > > 
> > > > pavel@...0:/sys/class/leds/lp5523:r/device$ ls -al engine*
> > > > -rw-r--r-- 1 root root 4096 Jul  6 22:47 engine1_leds
> > > > --w------- 1 root root 4096 Jul  6 22:47 engine1_load
> > > > -rw-r--r-- 1 root root 4096 Jul  6 23:41 engine1_mode
> > > > -rw-r--r-- 1 root root 4096 Jul  6 22:47 engine2_leds
> > > > --w------- 1 root root 4096 Jul  6 22:47 engine2_load
> > > > -rw-r--r-- 1 root root 4096 Jul  6 23:41 engine2_mode
> > > > -rw-r--r-- 1 root root 4096 Jul  6 22:47 engine3_leds
> > > > --w------- 1 root root 4096 Jul  6 22:47 engine3_load
> > > > -rw-r--r-- 1 root root 4096 Jul  6 22:47 engine3_mode
> > > > pavel@...0:/sys/class/leds/lp5523:r/device$ grep . engine*mode
> > > > engine1_mode:run
> > > > engine2_mode:load
> > > > engine3_mode:run
> > > > pavel@...0:/sys/class/leds/lp5523:r/device$
> > > 
> > > On 2.6.28 kernel is present only legacy interface and for this version
> > > is above documentation correct. When engine is in "run" or "disabled",
> > > then sysfs nodes _load and _leds are invisible.
> > 
> > Well, I don't think 2.6.28 is suitable kernel to compare
> > against... and I don't think hiding sysfs attributes makes any sense.
> 
> It is legacy interface which was used in older kernels (like 2.6.28) and
> is there to not break existing applications... So comparing with kernel
> when that interface was not legacy is correct way to check...

Well, not breaking legacy applications is only goal after reasonable
interface is merged to mainline.

Can you test if they actually care about the change or not? I suspect
they don't.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html