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From: Arnd Bergmann <arnd@arndb.de>
To: Boris Brezillon <boris.brezillon@bootlin.com>
Cc: Wolfram Sang <wsa@the-dreams.de>,
	Linux I2C <linux-i2c@vger.kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	gregkh <gregkh@linuxfoundation.org>,
	Przemyslaw Sroka <psroka@cadence.com>,
	Arkadiusz Golec <agolec@cadence.com>,
	Alan Douglas <adouglas@cadence.com>,
	Bartosz Folta <bfolta@cadence.com>, Damian Kos <dkos@cadence.com>,
	Alicja Jurasik-Urbaniak <alicja@cadence.com>,
	Cyprian Wronka <cwronka@cadence.com>,
	Suresh Punnoose <sureshp@cadence.com>,
	Rafal Ciepiela <rafalc@cadence.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Nishanth Menon <nm@ti.com>, Rob Herring <robh+dt@kernel.org>,
	Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>,
	DTML <devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Vitor Soares <Vitor.Soares@synopsys.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Xiang Lin <Xiang.Lin@synaptics.com>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	Sekhar Nori <nsekhar@ti.com>, Przemyslaw Gaj <pgaj@cadence.com>,
	Peter Rosin <peda@axentia.se>,
	mshettel@codeaurora.org, swboyd@chromium.org
Subject: Re: [PATCH v8 00/10] Add the I3C subsystem
Date: Mon, 8 Oct 2018 12:47:21 +0200
Message-ID: <CAK8P3a2C+FHiPnHKEAanhD=RpqDG1VywTEGhpdBvvKQ8zmwdUA@mail.gmail.com> (raw)
In-Reply-To: <20181003132212.12619-1-boris.brezillon@bootlin.com>

On Wed, Oct 3, 2018 at 3:22 PM Boris Brezillon
<boris.brezillon@bootlin.com> wrote:
>
> Sorry for the huge delay between v7 and v8 despite the small amount of
> things I was asked to fix/rework.
>
> This patch series is adding a new subsystem to support I3C devices.
>
> This is just adding support for basic features. Extra features will
> be added afterwards.
>
> There are a few design choices that are worth mentioning because they
> impact the way I3C device drivers can interact with their devices:
>
> - all functions used to send I3C/I2C frames must be called in
>   non-atomic context. Mainly done this way to ease implementation, but
>   this is still open to discussion. Please let me know if you think it's
>   worth considering an asynchronous model here
> - the I3C bus and I3C master controller are now tightly coupled even
>   though they're still allocated separately. There's now a 1:1
>   relationship between these objects, and the I3C master is no longer
>   represented under the I3C bus object.
>   Arnd, let me know if you had something different in mind, and I'll
>   rework the implementation accordingly.

I looked at the entire series again and I'm rather happy with how
it turned out. I've commented on a tiny issue about the readsl()
that should be easy to resolve one way or another, with that
you can add my

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

There is one additional issue that we've talked about previously
and that I'd like to hear about from GregKH or maybe other
subsystem maintainers: In the current version, you have a single
'bus_type' object, and this is used to represent both a 'host' and
a 'device'. I think we concluded that this is done in other
subsystems as well, and that this is fitting here because a
host (master device) can hand over being a master to another
device (slave), which then becomes the host and sees this
one as a slave. Also a lot of the sysfs attributes are the same
because of this relationship.

It also means that you get a mix of things in sysfs:

/sys/devices/i3c/<bus>
/sys/devices/i3c/<device>
/sys/devices/i3c/<bus>/<device>

which is a bit like what we have on USB where we can have hub
devices that are again parents of other USB devices, but I don't
think we can have i3c hubs or multiplexers in the same way, so
it's only a single level.

I'm ok with this model after our previous discussion and couldn't
come up with a better one. If anyone else still sees it as
problematic and has a better idea, please let us know now.

         Arnd

  parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-03 13:22 Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 01/10] i3c: Add core I3C infrastructure Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 02/10] docs: driver-api: Add I3C documentation Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 03/10] i3c: Add sysfs ABI spec Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 04/10] dt-bindings: i3c: Document core bindings Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 05/10] dt-bindings: i3c: Add macros to help fill I3C/I2C device's reg property Boris Brezillon
2018-10-03 18:37   ` Joe Perches
2018-10-03 18:45     ` Geert Uytterhoeven
2018-10-03 19:02       ` Joe Perches
2018-10-03 18:59     ` Boris Brezillon
2018-10-03 19:06       ` Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 06/10] MAINTAINERS: Add myself as the I3C subsystem maintainer Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 07/10] i3c: master: Add driver for Cadence IP Boris Brezillon
2018-10-08 10:06   ` Arnd Bergmann
2018-10-08 10:21     ` Boris Brezillon
2018-10-08 10:36       ` Arnd Bergmann
2018-10-08 12:05         ` Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 08/10] dt-bindings: i3c: Document Cadence I3C master bindings Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 09/10] gpio: Add a driver for Cadence I3C GPIO expander Boris Brezillon
2018-10-03 13:22 ` [PATCH v8 10/10] dt-bindings: gpio: Add bindings for Cadence I3C gpio expander Boris Brezillon
2018-10-04  8:35   ` Linus Walleij
2018-10-08 10:47 ` Arnd Bergmann [this message]
2018-10-17 13:18   ` [PATCH v8 00/10] Add the I3C subsystem Boris Brezillon

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