linux-kernel - Re: [PATCH v5 0/6] drivers/i2c: Add FSI-attached I2C master algorithm

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Date:   Tue, 15 Aug 2017 17:40:38 +0930
From:   Joel Stanley <joel@....id.au>
To:     Peter Rosin <peda@...ntia.se>
Cc:     Eddie James <eajames@...ux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c@...r.kernel.org, devicetree <devicetree@...r.kernel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Rob Herring <robh+dt@...nel.org>, Jeremy Kerr <jk@...abs.org>,
        Andrew Jeffery <andrew@...id.au>,
        Christopher Bostic <cbostic@...ux.vnet.ibm.com>,
        "Edward A. James" <eajames@...ibm.com>
Subject: Re: [PATCH v5 0/6] drivers/i2c: Add FSI-attached I2C master algorithm

On Tue, Aug 15, 2017 at 4:06 PM, Peter Rosin <peda@...ntia.se> wrote:
> On 2017-07-26 19:13, Eddie James wrote:
>> From: "Edward A. James" <eajames@...ibm.com>
>>
>> This series adds an algorithm for an I2C master physically located on an FSI
>> slave device. The I2C master has multiple ports, each of which may be connected
>> to an I2C slave. Access to the I2C master registers is achieved over FSI bus.
>>
>> Due to the multi-port nature of the I2C master, the driver instantiates a new
>> I2C adapter for each port connected to a slave. The connected ports should be
>> defined in the device tree under the I2C master device.
>
> Hmmm, AFAIU fsi is a bus, and on this bus you have some "client" device that
> happens to be an i2c master, and this is a driver for that "client". Is it
> totally inconceivable to have some other client device in the future that is
> implementing an i2c master differently, but still using the fsi bus?
>
> With that in mind, is it wise to pick the driver name from the bus that the
> device is connected to, and nothing else without further qualification?
>
> I don't see any "i2c-usb" driver, but I think there are a couple of i2c master
> drivers that communicate via usb.

You make a fair point. When I did a prototype of this driver I called
it i2c-cfam, as it is part of the CFAM hardware unit inside of the
Power8/Power9 processors.

The documentation does call it FSI_I2CM, so that's an argument for the
current name.

I'm not sure how accurate that name is. Chris, Eddie, do you have any
other suggestions?

Cheers,

Joel