linux-kernel - Re: [PATCH linux v7 3/6] hwmon: occ: Add I2C transport implementation for SCOM operations

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Date:   Mon, 13 Feb 2017 11:42:13 +1030
From:   Andrew Jeffery <andrew@...id.au>
To:     Eddie James <eajames@...ux.vnet.ibm.com>,
        Joel Stanley <joel@....id.au>
Cc:     Guenter Roeck <linux@...ck-us.net>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-doc@...r.kernel.org, jdelvare@...e.com, corbet@....net,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Edward A. James" <eajames@...ibm.com>
Subject: Re: [PATCH linux v7 3/6] hwmon: occ: Add I2C transport
 implementation for SCOM operations

On Fri, 2017-02-10 at 15:05 -0600, Eddie James wrote:
> On 02/09/2017 11:31 PM, Joel Stanley wrote:
> > > On Wed, Feb 8, 2017 at 9:40 AM,<eajames@...ux.vnet.ibm.com>  wrote:
> > >> From: "Edward A. James"<eajames@...ibm.com>
> >>
> >> Add functions to send SCOM operations over I2C bus. The BMC can
> >> communicate with the Power8 host processor over I2C, but needs to use SCOM
> >> operations in order to access the OCC register space.
> > This doesn't need to be separate from the p8_occ_i2c.c file. You can
> > remove a layer of function calls by merging this in and having these
> > be your getscom putscom bus_ops callbacks.
> 
> The purpose of having this separate was so that we could do the scom 
> address shift for p8 separately.

Separation was my suggestion. It makes the I2C transport implementation
independent of any P8 details, and having it separate* is no more
abstract than the core performing SCOMs through the FSI interface when
that's available. I feel like it's muddying the waters conceptually to
bury P8 details in the implementation of a SCOM transport layer.

However, in our less abstract world the P8 will be the only system that
uses the I2C transport, so while I don't think merging the functions is
a good idea from an abstraction perspective it won't have a big impact.

Andrew

* Maybe the I2C SCOM transport even deserves to live outside
drivers/hwmon/occ?
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