linux-kernel - Re: [PATCH v5 2/4] leds: simatic-ipc-leds: add new driver for Siemens Industial PCs

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Message-ID: <20211220091434.2f696d76@md1za8fc.ad001.siemens.net>
Date:   Mon, 20 Dec 2021 09:14:34 +0100
From:   Henning Schild <henning.schild@...mens.com>
To:     Pavel Machek <pavel@....cz>
CC:     Hans de Goede <hdegoede@...hat.com>,
        <linux-kernel@...r.kernel.org>, <linux-leds@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>,
        <linux-watchdog@...r.kernel.org>,
        Srikanth Krishnakar <skrishnakar@...il.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        "Gerd Haeussler" <gerd.haeussler.ext@...mens.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Mark Gross <mgross@...ux.intel.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Enrico Weigelt <lkml@...ux.net>
Subject: Re: [PATCH v5 2/4] leds: simatic-ipc-leds: add new driver for
 Siemens Industial PCs

Am Mon, 20 Dec 2021 08:53:55 +0100
schrieb Henning Schild <henning.schild@...mens.com>:

> Am Sun, 19 Dec 2021 17:49:03 +0100
> schrieb Pavel Machek <pavel@....cz>:
> 
> > On Wed 2021-12-15 21:53:56, Hans de Goede wrote:  
> > > Hi,
> > > 
> > > On 12/15/21 21:18, Pavel Machek wrote:    
> > > > On Mon 2021-12-13 13:05:00, Henning Schild wrote:    
> > > >> This driver adds initial support for several devices from
> > > >> Siemens. It is based on a platform driver introduced in an
> > > >> earlier commit.
> > > >>
> > > >> One of the supported machines has GPIO connected LEDs, here we
> > > >> poke GPIO memory directly because pinctrl does not come up.
> > > >>
> > > >> Signed-off-by: Henning Schild <henning.schild@...mens.com>    
> > > > 
> > > > Acked-by: Pavel Machek <pavel@....cz>    
> > > 
> > > I see that this patch #includes
> > > linux/platform_data/x86/simatic-ipc-base.h which gets added by
> > > patch 1/4.
> > > 
> > > Pavel, can I take this patch upstream through the pdx86 tree (with
> > > you Ack added)? Or shall I prepare an immutable branch with patch
> > > 1 for you to merge ?    
> > 
> > Yes, you can.
> > 
> >   
> > > >> +
> > > >> +static struct simatic_ipc_led simatic_ipc_leds_io[] = {
> > > >> +	{1 << 15, "green:" LED_FUNCTION_STATUS "-1" },
> > > >> +	{1 << 7,  "yellow:" LED_FUNCTION_STATUS "-1" },
> > > >> +	{1 << 14, "red:" LED_FUNCTION_STATUS "-2" },
> > > >> +	{1 << 6,  "yellow:" LED_FUNCTION_STATUS "-2" },
> > > >> +	{1 << 13, "red:" LED_FUNCTION_STATUS "-3" },
> > > >> +	{1 << 5,  "yellow:" LED_FUNCTION_STATUS "-3" },
> > > >> +	{ }
> > > >> +};    
> > 
> > But I'd still like better naming than red:status-2.  
> 
> We had the name discussion already several times, and i have to admit
> i am not too happy either.
> 
> But my impression was that this is an acceptable compromise. I am not
> happy because the names lack scope, which i had in the first round
> with "simatic-ipc:red:...".
> 
> Function is also a bit unclear, but with the numbers and the user
> manual, or looking at the chassis it kind of adds up and should be
> clear to users which is which.
> 
> But i agree with Hans that we should sort this out before merge. So
> please say what makes you unhappy, maybe that can be fixed ... might
> even make me happier about the names i feel i had to choose.
> 
> The LEDs are per definition of the manuals meant for
> users/applications to signal whatever the use-case might want to
> signal. There are 3 of them numbered 1-3 on the chassis, and next to
> the number can often (not always) be found a string like "error",
> "maint", "run-stop" So a function suggestion i would say.
> 
> I could envision to use "fault" or "alarm" instead of "status" for the
> one labeled "error". And maybe "standby" for the one called "maint"
> but i would really like to keep the numbers.
> 
> Which would look like
> 
> status-1
> alarm-2
> standby-3
> 
> But still i have to clue what those names stand for and choosing
> and of those "undefined" names could just suggest things and break
> expectations. Calling them all "status" is neutral ... 
> 
> Or can you explain the difference between "fault", "panic" and
> "alarm". Ask 5 people and get at least 3 different expectations ... i
> guess.

Long story short, i am also not happy but the current suggestion is the
most generic and least "expectation-creating" i could come up with.
While keeping a mapping between the name and the chassis/manual.

So i will stick with it, unless i get concrete suggestions on how to
improve.

The misc functions
https://elixir.bootlin.com/linux/latest/source/include/dt-bindings/leds/common.h#L63

do not seem usable. Without a set of conventions they are nothing but
"allowed but undefined strings". I could however introduce
FUNCTION_ERROR FUNCTION_MAINT FUNCTION_RUN_STOP ... add more such random
strings. Which would probably make me happy because it would create a
better mapping between the names and the chassis ... but it would
worsen the problem of "what are those misc functions anyway?"

Henning

> Henning
> 
> 
> > 								Pavel
> >  
>