From: Lee Jones <lee.jones@linaro.org>
To: Rob Herring <robh+dt@kernel.org>
Cc: "Michael Walle" <michael@walle.cc>,
"Andy Shevchenko" <andy.shevchenko@gmail.com>,
"Ranjani Sridharan" <ranjani.sridharan@linux.intel.com>,
david.m.ertman@intel.com, shiraz.saleem@intel.com,
"Mark Brown" <broonie@kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
devicetree <devicetree@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Linux HWMON List" <linux-hwmon@vger.kernel.org>,
"Linux PWM List" <linux-pwm@vger.kernel.org>,
LINUX-WATCHDOG <linux-watchdog@vger.kernel.org>,
"linux-arm Mailing List" <linux-arm-kernel@lists.infradead.org>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Bartosz Golaszewski" <bgolaszewski@baylibre.com>,
"Jean Delvare" <jdelvare@suse.com>,
"Guenter Roeck" <linux@roeck-us.net>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Wim Van Sebroeck" <wim@linux-watchdog.org>,
"Shawn Guo" <shawnguo@kernel.org>, "Li Yang" <leoyang.li@nxp.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Jason Cooper" <jason@lakedaemon.net>,
"Marc Zyngier" <maz@kernel.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>
Subject: Re: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller
Date: Wed, 10 Jun 2020 19:02:41 +0100 [thread overview]
Message-ID: <20200610180241.GU4106@dell> (raw)
In-Reply-To: <CAL_JsqKr1aDVzgAMjwwK8E8O_f29vSrx1HXk81FF+rd3sEe==w@mail.gmail.com>
On Wed, 10 Jun 2020, Rob Herring wrote:
> On Wed, Jun 10, 2020 at 1:19 AM Lee Jones <lee.jones@linaro.org> wrote:
> >
> > On Wed, 10 Jun 2020, Michael Walle wrote:
> > > Am 2020-06-09 21:45, schrieb Lee Jones:
> > > > On Tue, 09 Jun 2020, Michael Walle wrote:
> > > > > > We do not need a 'simple-regmap' solution for your use-case.
> > > > > >
> > > > > > Since your device's registers are segregated, just split up the
> > > > > > register map and allocate each sub-device with it's own slice.
> > > > >
> > > > > I don't get it, could you make a device tree example for my
> > > > > use-case? (see also above)
> > > >
> > > > &i2cbus {
> > > > mfd-device@10 {
> > > > compatible = "simple-mfd";
> > > > reg = <10>;
> > > >
> > > > sub-device@10 {
> > > > compatible = "vendor,sub-device";
> > > > reg = <10>;
> > > > };
> > > > };
> > > >
> > > > The Regmap config would be present in each of the child devices.
> > > >
> > > > Each child device would call devm_regmap_init_i2c() in .probe().
> > >
> > > Ah, I see. If I'm not wrong, this still means to create an i2c
> > > device driver with the name "simple-mfd".
> >
> > Yes, it does.
>
> TBC, while fine for a driver to bind on 'simple-mfd', a DT compatible
> with that alone is not fine.
'simple-mfd' essentially means:
"This device doesn't do anything useful, but the children do."
When used with 'syscon' it means:
"Memory for this device is shared between all children"
Adding more specific/descriptive compatible strings is conceptually
fine, but they should not be forced to bind to a real driver using
them. Else we're creating drivers for the sake of creating drivers.
This is especially true with 'simple-mfd' is used without 'syscon'.
> > > Besides that, I don't like this, because:
> > > - Rob already expressed its concerns with "simple-mfd" and so on.
> >
> > Where did this take place? I'd like to read up on this.
> >
> > > - you need to duplicate the config in each sub device
> >
> > You can have a share a single config.
> >
> > > - which also means you are restricting the sub devices to be
> > > i2c only (unless you implement and duplicate other regmap configs,
> > > too). For this driver, SPI and MMIO may be viable options.
> >
> > You could also have a shared implementation to choose between different
> > busses.
>
> I think it is really the syscon mfd driver you want to generalize to
> other buses. Though with a quick look at it, there's not really a
> whole lot to share. The regmap lookup would be the main thing. You are
> going to need a driver instance for each bus type.
On it.
--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog
next prev parent reply other threads:[~2020-06-10 18:02 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-04 21:10 [PATCH v4 00/11] Add support for Kontron sl28cpld Michael Walle
2020-06-04 21:10 ` [PATCH v4 01/11] dt-bindings: mfd: Add bindings for sl28cpld Michael Walle
2020-06-09 16:28 ` Rob Herring
2020-06-04 21:10 ` [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller Michael Walle
2020-06-05 6:57 ` Lee Jones
2020-06-05 9:51 ` Michael Walle
2020-06-05 10:50 ` Mark Brown
2020-06-05 20:07 ` Michael Walle
2020-06-06 11:46 ` Mark Brown
2020-06-06 12:45 ` Michael Walle
2020-06-08 8:28 ` Lee Jones
2020-06-08 10:02 ` Andy Shevchenko
2020-06-08 15:41 ` Michael Walle
2020-06-08 18:56 ` Lee Jones
2020-06-08 21:09 ` Michael Walle
2020-06-09 6:47 ` Lee Jones
2020-06-09 14:38 ` Michael Walle
2020-06-09 14:42 ` Mark Brown
2020-06-09 15:01 ` Michael Walle
2020-06-09 17:15 ` Rob Herring
2020-06-09 17:29 ` Mark Brown
2020-06-09 18:41 ` Lee Jones
2020-06-09 15:19 ` Lee Jones
2020-06-09 15:30 ` Michael Walle
2020-06-09 19:45 ` Lee Jones
2020-06-10 7:10 ` Michael Walle
2020-06-10 7:19 ` Lee Jones
2020-06-10 7:49 ` Michael Walle
2020-06-10 7:56 ` Lee Jones
2020-06-10 9:27 ` Michael Walle
2020-06-10 18:30 ` Lee Jones
2020-06-10 17:16 ` Rob Herring
2020-06-10 18:02 ` Lee Jones [this message]
2020-06-08 18:20 ` Lee Jones
2020-06-09 16:54 ` Rob Herring
2020-06-09 18:52 ` Lee Jones
2020-06-05 8:01 ` Andy Shevchenko
2020-06-05 8:02 ` Andy Shevchenko
2020-06-05 10:09 ` Michael Walle
2020-06-05 10:48 ` Andy Shevchenko
2020-06-05 11:51 ` Michael Walle
2020-06-04 21:10 ` [PATCH v4 03/11] irqchip: add sl28cpld interrupt controller support Michael Walle
2020-06-05 1:26 ` kernel test robot
2020-06-05 8:07 ` Andy Shevchenko
2020-06-08 15:12 ` kernel test robot
2020-06-04 21:10 ` [PATCH v4 04/11] watchdog: add support for sl28cpld watchdog Michael Walle
2020-06-05 8:14 ` Andy Shevchenko
2020-06-05 10:24 ` Michael Walle
2020-06-05 10:50 ` Andy Shevchenko
2020-06-05 13:52 ` Guenter Roeck
2020-06-05 14:09 ` Andy Shevchenko
2020-06-05 15:05 ` Guenter Roeck
2020-06-05 16:04 ` Andy Shevchenko
2020-06-05 16:34 ` Guenter Roeck
2020-06-04 21:10 ` [PATCH v4 05/11] pwm: add support for sl28cpld PWM controller Michael Walle
2020-06-05 8:15 ` Andy Shevchenko
2020-06-05 8:49 ` Lee Jones
2020-06-05 9:33 ` Andy Shevchenko
2020-06-05 11:39 ` Michael Walle
2020-06-05 18:17 ` Michael Walle
2020-06-08 7:46 ` Lee Jones
2020-06-04 21:10 ` [PATCH v4 06/11] gpio: add support for the sl28cpld GPIO controller Michael Walle
2020-06-05 12:00 ` Andy Shevchenko
2020-06-05 12:42 ` Michael Walle
2020-06-05 13:15 ` Andy Shevchenko
2020-06-05 18:44 ` Michael Walle
2020-06-05 21:19 ` Andy Shevchenko
2020-06-04 21:10 ` [PATCH v4 07/11] hwmon: add support for the sl28cpld hardware monitoring controller Michael Walle
2020-06-05 12:06 ` Andy Shevchenko
2020-06-04 21:10 ` [PATCH v4 08/11] arm64: dts: freescale: sl28: enable sl28cpld Michael Walle
2020-06-04 21:10 ` [PATCH v4 09/11] arm64: dts: freescale: sl28: map GPIOs to input events Michael Walle
2020-06-04 21:10 ` [PATCH v4 10/11] arm64: dts: freescale: sl28: enable LED support Michael Walle
2020-06-04 21:10 ` [PATCH v4 11/11] arm64: dts: freescale: sl28: enable fan support Michael Walle
2020-06-05 6:13 ` [PATCH v4 00/11] Add support for Kontron sl28cpld Lee Jones
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200610180241.GU4106@dell \
--to=lee.jones@linaro.org \
--cc=andriy.shevchenko@linux.intel.com \
--cc=andy.shevchenko@gmail.com \
--cc=bgolaszewski@baylibre.com \
--cc=broonie@kernel.org \
--cc=david.m.ertman@intel.com \
--cc=devicetree@vger.kernel.org \
--cc=gregkh@linuxfoundation.org \
--cc=jason@lakedaemon.net \
--cc=jdelvare@suse.com \
--cc=leoyang.li@nxp.com \
--cc=linus.walleij@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-gpio@vger.kernel.org \
--cc=linux-hwmon@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pwm@vger.kernel.org \
--cc=linux-watchdog@vger.kernel.org \
--cc=linux@roeck-us.net \
--cc=maz@kernel.org \
--cc=michael@walle.cc \
--cc=ranjani.sridharan@linux.intel.com \
--cc=robh+dt@kernel.org \
--cc=shawnguo@kernel.org \
--cc=shiraz.saleem@intel.com \
--cc=tglx@linutronix.de \
--cc=thierry.reding@gmail.com \
--cc=u.kleine-koenig@pengutronix.de \
--cc=wim@linux-watchdog.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).