linux-kernel - Re: outdated documentation for lp5523 LED driver?

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Date:	Fri, 15 Jul 2016 09:40:52 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Pavel Machek <pavel@....cz>
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Subject: Re: outdated documentation for lp5523 LED driver?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 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.

So I suspect that bug is in current kernel code and documentation is
correct... So I would propose to fix kernel code to reflect
documentation...

> I got both the legacy and the firmware interface to work... but the
> firmware interface only seems to work once for me.
> 
> How new and old interface are expected to interact with each other is
> not clear to me.

In my opinion both interfaces could be used. They provide same states
load/run but via different sysfs files.

> What should be done there?
> 
> Best regards,
> 									Pavel
> 

-- 
Pali Rohár
pali.rohar@...il.com