Re: [PATCH v2 2/4] leds: simatic-ipc-leds: add new driver for Siemens Industial PCs

From: Henning Schild <henning.schild@siemens.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux LED Subsystem <linux-leds@vger.kernel.org>,
	Platform Driver <platform-driver-x86@vger.kernel.org>,
	<linux-watchdog@vger.kernel.org>,
	Srikanth Krishnakar <skrishnakar@gmail.com>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Gerd Haeussler <gerd.haeussler.ext@siemens.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Mark Gross <mgross@linux.intel.com>,
	Hans de Goede <hdegoede@redhat.com>
Subject: Re: [PATCH v2 2/4] leds: simatic-ipc-leds: add new driver for Siemens Industial PCs
Date: Mon, 15 Mar 2021 13:40:50 +0100	[thread overview]
Message-ID: <20210315134037.7f8529e7@md1za8fc.ad001.siemens.net> (raw)
In-Reply-To: <20210315111915.GA14857@duo.ucw.cz>

Am Mon, 15 Mar 2021 12:19:15 +0100
schrieb Pavel Machek <pavel@ucw.cz>:

> > > +       struct led_classdev cdev;
> > > +};
> > > +
> > > +static struct simatic_ipc_led simatic_ipc_leds_io[] = {
> > > +       {1 << 15, "simatic-ipc:green:" LED_FUNCTION_STATUS "-1" },
> > > +       {1 << 7,  "simatic-ipc:yellow:" LED_FUNCTION_STATUS "-1"
> > > },
> > > +       {1 << 14, "simatic-ipc:red:" LED_FUNCTION_STATUS "-2" },
> > > +       {1 << 6,  "simatic-ipc:yellow:" LED_FUNCTION_STATUS "-2"
> > > },
> > > +       {1 << 13, "simatic-ipc:red:" LED_FUNCTION_STATUS "-3" },
> > > +       {1 << 5,  "simatic-ipc:yellow:" LED_FUNCTION_STATUS "-3"
> > > },  
> > 
> > Can you use BIT() macro here? And can it be sorted by the bit
> > order?  
> 
> There's nothing wrong with << and this order is fine.
> 
> But I still don't like the naming. simantic-ipc: prefix is
> useless. Having 6 status leds is not good, either.

You asked about a picture before, so here is one example

https://support.industry.siemens.com/cs/document/67235073/simatic-ipc427d?dti=0&pnid=16756&lc=en-WW

page 19 shows how the box looks like
page 135 it what the implementation is based on

Externally human visible are 3 "lights", which can be off, red, green,
yellow. Internally every single "light" has two leds and yellow is a
mix when red and green are on.
Unfortunately hw does not allow all 4 states for all 3 lights. Some
boxes implement "yellow" mixing in hw.

That is why the same name is used with two colors.

maybe those LEDs qualify for multi-color? 

"status" was the best name i found in the dt-bindings header

i guess i can be creative with the names and take ie "status", "fault",
and "indicator"

i will also drop that prefix "simatic-ipc" that was inspired by
"tpacpi", or should it be "platform:<color>:<name>"?

regards,
Henning

> > > +       struct simatic_ipc_led *led =
> > > +               container_of(led_cd, struct simatic_ipc_led,
> > > cdev);  
> > 
> > One line?  
> 
> 80 columns. It is fine as it is.
> 
> Best regards,
> 
> 								Pavel