From: Marc Dietrich <marvin24@gmx.de>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC 4/4] ARM: shmobile: r8a7790: adapt DTS for I2C slave support
Date: Thu, 11 Sep 2014 14:49:39 +0000 [thread overview]
Message-ID: <1848352.9OlbbQfLfy@fb07-iapwap2> (raw)
In-Reply-To: <20140911141257.GC5149@katana>
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Am Donnerstag, 11. September 2014, 16:12:58 schrieb Wolfram Sang:
> On Thu, Sep 11, 2014 at 02:17:16PM +0200, Marc Dietrich wrote:
> > > + reg = <0x64>;
> >
> > we had some discussions in the past how to represent i2c master devices in
> > device tree. The outcome was to use to a special representation to
> > distinguish them from slave devices, e.g. something like reg = <0x1
> > 0x64>, where the 0x1 would mean "master" device (0x0 -> slave). If
> > nothing is added, then it's also slave. The adapter address cell would
> > also need to be changed if this extension is used.
>
> Please don't change the reg-layout which is around since forever.
> It will break all existing devicetrees. NAK.
it won't break existing device trees. It would only need to be extended for
systems where the adapter uses master and slave modes (or if you add a master
device to the i2c client list). So you need to change the device tree anyway.
All other setups can continue to use a single reg.
Thinking more about it, are there any i2c clients parsing the reg property
directly? In this case I would agree, otherwise, only i2c core needs some
update - right?
Marc
> > An alternative would be to use a special property (e.g. slave address),
> > but
> > that would encode the same value twice (or even three times).
>
> As said, if all breaks we handle it at runtime.
>
> Thanks,
>
> Wolfram
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WARNING: multiple messages have this Message-ID (diff)
From: Marc Dietrich <marvin24@gmx.de>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-i2c@vger.kernel.org, linux-sh@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Jean Delvare <jdelvare@suse.de>,
Magnus Damm <magnus.damm@gmail.com>,
Andrey Danin <danindrey@mail.ru>,
devicetree@vger.kernel.org,
Stephen Warren <swarren@wwwdotorg.org>
Subject: Re: [RFC 4/4] ARM: shmobile: r8a7790: adapt DTS for I2C slave support
Date: Thu, 11 Sep 2014 16:49:39 +0200 [thread overview]
Message-ID: <1848352.9OlbbQfLfy@fb07-iapwap2> (raw)
In-Reply-To: <20140911141257.GC5149@katana>
[-- Attachment #1: Type: text/plain, Size: 1393 bytes --]
Am Donnerstag, 11. September 2014, 16:12:58 schrieb Wolfram Sang:
> On Thu, Sep 11, 2014 at 02:17:16PM +0200, Marc Dietrich wrote:
> > > + reg = <0x64>;
> >
> > we had some discussions in the past how to represent i2c master devices in
> > device tree. The outcome was to use to a special representation to
> > distinguish them from slave devices, e.g. something like reg = <0x1
> > 0x64>, where the 0x1 would mean "master" device (0x0 -> slave). If
> > nothing is added, then it's also slave. The adapter address cell would
> > also need to be changed if this extension is used.
>
> Please don't change the reg-layout which is around since forever.
> It will break all existing devicetrees. NAK.
it won't break existing device trees. It would only need to be extended for
systems where the adapter uses master and slave modes (or if you add a master
device to the i2c client list). So you need to change the device tree anyway.
All other setups can continue to use a single reg.
Thinking more about it, are there any i2c clients parsing the reg property
directly? In this case I would agree, otherwise, only i2c core needs some
update - right?
Marc
> > An alternative would be to use a special property (e.g. slave address),
> > but
> > that would encode the same value twice (or even three times).
>
> As said, if all breaks we handle it at runtime.
>
> Thanks,
>
> Wolfram
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WARNING: multiple messages have this Message-ID (diff)
From: marvin24@gmx.de (Marc Dietrich)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC 4/4] ARM: shmobile: r8a7790: adapt DTS for I2C slave support
Date: Thu, 11 Sep 2014 16:49:39 +0200 [thread overview]
Message-ID: <1848352.9OlbbQfLfy@fb07-iapwap2> (raw)
In-Reply-To: <20140911141257.GC5149@katana>
Am Donnerstag, 11. September 2014, 16:12:58 schrieb Wolfram Sang:
> On Thu, Sep 11, 2014 at 02:17:16PM +0200, Marc Dietrich wrote:
> > > + reg = <0x64>;
> >
> > we had some discussions in the past how to represent i2c master devices in
> > device tree. The outcome was to use to a special representation to
> > distinguish them from slave devices, e.g. something like reg = <0x1
> > 0x64>, where the 0x1 would mean "master" device (0x0 -> slave). If
> > nothing is added, then it's also slave. The adapter address cell would
> > also need to be changed if this extension is used.
>
> Please don't change the reg-layout which is around since forever.
> It will break all existing devicetrees. NAK.
it won't break existing device trees. It would only need to be extended for
systems where the adapter uses master and slave modes (or if you add a master
device to the i2c client list). So you need to change the device tree anyway.
All other setups can continue to use a single reg.
Thinking more about it, are there any i2c clients parsing the reg property
directly? In this case I would agree, otherwise, only i2c core needs some
update - right?
Marc
> > An alternative would be to use a special property (e.g. slave address),
> > but
> > that would encode the same value twice (or even three times).
>
> As said, if all breaks we handle it at runtime.
>
> Thanks,
>
> Wolfram
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next prev parent reply other threads:[~2014-09-11 14:49 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-09 14:54 [RFC 0/4] i2c: slave support framework for Linux devices Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` [RFC 1/4] i2c: core changes for slave support Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` [RFC 2/4] i2c: slave: add eeprom simulator driver Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 16:34 ` Wolfram Sang
2014-09-09 16:34 ` Wolfram Sang
2014-09-09 16:34 ` Wolfram Sang
2014-09-09 14:54 ` [RFC 3/4] i2c: rcar: add slave support Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` [RFC 4/4] ARM: shmobile: r8a7790: adapt DTS for I2C " Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-09 14:54 ` Wolfram Sang
2014-09-11 12:17 ` Marc Dietrich
2014-09-11 12:17 ` Marc Dietrich
2014-09-11 12:17 ` Marc Dietrich
2014-09-11 14:12 ` Wolfram Sang
2014-09-11 14:12 ` Wolfram Sang
2014-09-11 14:12 ` Wolfram Sang
2014-09-11 14:12 ` Wolfram Sang
2014-09-11 14:40 ` Wolfram Sang
2014-09-11 14:40 ` Wolfram Sang
2014-09-11 14:40 ` Wolfram Sang
2014-09-11 14:52 ` Marc Dietrich
2014-09-11 14:52 ` Marc Dietrich
2014-09-11 14:52 ` Marc Dietrich
2014-09-11 14:52 ` Marc Dietrich
2014-09-11 14:54 ` Wolfram Sang
2014-09-11 14:54 ` Wolfram Sang
2014-09-11 14:54 ` Wolfram Sang
2014-09-12 7:51 ` Marc Dietrich
2014-09-12 7:51 ` Marc Dietrich
2014-09-12 7:51 ` Marc Dietrich
2014-09-12 7:51 ` Marc Dietrich
2014-09-12 8:08 ` Geert Uytterhoeven
2014-09-12 8:08 ` Geert Uytterhoeven
2014-09-12 8:08 ` Geert Uytterhoeven
2014-09-12 8:08 ` Geert Uytterhoeven
2014-09-12 8:33 ` Wolfram Sang
2014-09-12 8:33 ` Wolfram Sang
2014-09-12 8:33 ` Wolfram Sang
2014-09-12 8:33 ` Wolfram Sang
2014-09-12 9:06 ` Marc Dietrich
2014-09-12 9:06 ` Marc Dietrich
2014-09-12 9:06 ` Marc Dietrich
2014-09-12 9:58 ` Wolfram Sang
2014-09-12 9:58 ` Wolfram Sang
2014-09-12 9:58 ` Wolfram Sang
2014-09-12 10:10 ` Geert Uytterhoeven
2014-09-12 10:10 ` Geert Uytterhoeven
2014-09-12 10:10 ` Geert Uytterhoeven
2014-09-12 10:10 ` Geert Uytterhoeven
2014-09-12 10:26 ` Wolfram Sang
2014-09-12 10:26 ` Wolfram Sang
2014-09-12 10:26 ` Wolfram Sang
2014-09-12 10:26 ` Wolfram Sang
2014-09-12 11:42 ` Marc Dietrich
2014-09-12 11:42 ` Marc Dietrich
2014-09-12 11:42 ` Marc Dietrich
2014-09-12 12:15 ` Wolfram Sang
2014-09-12 12:15 ` Wolfram Sang
2014-09-12 12:15 ` Wolfram Sang
2014-09-11 14:49 ` Marc Dietrich [this message]
2014-09-11 14:49 ` Marc Dietrich
2014-09-11 14:49 ` Marc Dietrich
2014-09-11 12:06 ` [RFC 0/4] i2c: slave support framework for Linux devices Marc Dietrich
2014-09-11 12:06 ` Marc Dietrich
2014-09-11 12:06 ` Marc Dietrich
2014-09-12 8:58 ` Uwe Kleine-König
2014-09-12 8:58 ` Uwe Kleine-König
2014-09-12 8:58 ` Uwe Kleine-König
2014-09-12 8:58 ` Uwe Kleine-König
2014-09-12 9:12 ` Wolfram Sang
2014-09-12 9:12 ` Wolfram Sang
2014-09-12 9:12 ` Wolfram Sang
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