Re: [PATCH v3 2/4] leds: simatic-ipc-leds: add new driver for Siemens Industial PCs

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Henning Schild <henning.schild@siemens.com>
Cc: 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>, Pavel Machek <pavel@ucw.cz>,
	Enrico Weigelt <lkml@metux.net>
Subject: Re: [PATCH v3 2/4] leds: simatic-ipc-leds: add new driver for Siemens Industial PCs
Date: Tue, 30 Mar 2021 15:15:16 +0300	[thread overview]
Message-ID: <CAHp75Vc0f0HfAJx0KPyQMWjekkhB_T-1+vuR566qAcYGA2JLJA@mail.gmail.com> (raw)
In-Reply-To: <20210330135808.373c3308@md1za8fc.ad001.siemens.net>

On Tue, Mar 30, 2021 at 2:58 PM Henning Schild
<henning.schild@siemens.com> wrote:
> Am Tue, 30 Mar 2021 14:04:35 +0300
> schrieb Andy Shevchenko <andy.shevchenko@gmail.com>:
> > On Mon, Mar 29, 2021 at 8:59 PM Henning Schild
> > <henning.schild@siemens.com> wrote:
> > >
> > > This driver adds initial support for several devices from Siemens.
> > > It is based on a platform driver introduced in an earlier commit.
> >
> > ...
> >
> > > +#define SIMATIC_IPC_LED_PORT_BASE      0x404E
> >
> > > +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" },
> > > +       { }
> > > +};
> >
> > > +static struct simatic_ipc_led simatic_ipc_leds_mem[] = {
> > > +       {0x500 + 0x1A0, "red:" LED_FUNCTION_STATUS "-1"},
> > > +       {0x500 + 0x1A8, "green:" LED_FUNCTION_STATUS "-1"},
> > > +       {0x500 + 0x1C8, "red:" LED_FUNCTION_STATUS "-2"},
> > > +       {0x500 + 0x1D0, "green:" LED_FUNCTION_STATUS "-2"},
> > > +       {0x500 + 0x1E0, "red:" LED_FUNCTION_STATUS "-3"},
> > > +       {0x500 + 0x198, "green:" LED_FUNCTION_STATUS "-3"},
> > > +       { }
> > > +};
> >
> > It seems to me like poking GPIO controller registers directly. This
> > is not good. The question still remains: Can we simply register a
> > GPIO (pin control) driver and use an LED GPIO driver with an
> > additional board file that instantiates it?
>
> I wrote about that in reply to the cover letter. My view is still that
> it would be an abstraction with only one user, just causing work and
> likely not ending up as generic as it might eventually have to be.
>
> The region is reserved, not sure what the problem with the "poking" is.

> Maybe i do not understand all the benefits of such a split at this
> point in time. At the moment i only see work with hardly any benefit,
> not just work for me but also for maintainers. I sure do not mean to be
> ignorant. Maybe you go into details and convince me or we wait for other
> peoples opinions on how to proceed, maybe there is a second user that i
> am not aware of?
> Until i am convinced otherwise i will try to argue that a
> single-user-abstraction is needless work/code, and should be done only
> when actually needed.

I have just read your messages (there is a cover letter and additional
email which was sent lately).

I would like to know what the CPU model number on that board is. Than
we can continue to see what possibilities we have here.

-- 
With Best Regards,
Andy Shevchenko