linux-kernel - Re: [PATCH v5 1/4] i2c: busses: i2c-st: Add ST I2C controller

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Message-ID: <525FF498.3060202@st.com>
Date:	Thu, 17 Oct 2013 15:30:48 +0100
From:	srinivas kandagatla <srinivas.kandagatla@...com>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Cc:	Maxime COQUELIN <maxime.coquelin@...com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Landley <rob@...dley.net>,
	Russell King <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	Stuart MENEFY <stuart.menefy@...com>,
	Lee Jones <lee.jones@...aro.org>,
	Stephen GALLIMORE <stephen.gallimore@...com>,
	Gabriel FERNANDEZ <gabriel.fernandez@...com>
Subject: Re: [PATCH v5 1/4] i2c: busses: i2c-st: Add ST I2C controller

On 17/10/13 15:19, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 10:33 Thu 17 Oct     , srinivas kandagatla wrote:
>> On 17/10/13 08:27, Maxime COQUELIN wrote:
>>> ...
>>>>>>> +
>>>>>>> +static struct of_device_id st_i2c_match[] = {
>>>>>>> +     { .compatible = "st,comms-ssc-i2c", },
>>>>> the rules is to put the first soc that use the ip in the compatible
>>>>> as st,sti7100-scc-i2c
>>> Ok. There are no plans to upstream the SH4 platforms, it will only 
>>> remains in stlinux.com.
>>> Maybe I can set the first ARM platform (STiH415)?
>>> That would give st,stih415-ssc-i2c.
>> NAK, for st,stih415-ssc-i2c naming.
>>
>> IMO, this makes sense when the same IP integration done on different SOC
>> changes slightly/very differently.
>>
>> But in this case the "comms" IP remains unchanged across all the SOCs.
>>
>> I would still prefer "st,comms-ssc-i2c", allowing a single device driver
>> to match against several SoCs. ST "comms" IP it is integrated across all
>> the STi series of SoCs, so we don't want to add new entry in compatible
>> for every new SOC.
> 
> you never need this you always the first SoC that's all

Sorry to ask this but, Where is this requirement coming from?
I have not spotted any thing as such in ePAPR specs.

All the spec says is.
===
The compatible property value consists of one or more strings that
define the specific programming model for the device. This list of
strings should be used by a client program for device driver selection.
The property value consists of a concatenated list of null terminated
strings, *from most specific to most general.* They allow a device to
express its compatibility with a family of similar devices, potentially
allowing a single device driver to match against several devices.
The recommended format is “manufacturer,model”, where manufacturer is a
string describing the name of the manufacturer (such as an OUI), and
model specifies the model number.

Example:
compatible = “fsl,mpc8641-uart”, “ns16550";
In this example, an operating system would first try to locate a device
driver that supported fsl,mpc8641-uart. If a driver was not found, it
would then try to locate a driver that supported the more general
ns16550 device type.
===

The more general compatible string in this case is "st,comms-ssc-i2c",
rather than the first soc name.
How can a first SOC name be more general?

As this driver is not very specific to StiH415, it is generic driver for
ST comms-ssc-i2c block.

Thanks,
srini

> 
> see other bindings on at91 as example sorry NACK
> 
> Best Regards,
> J.
>>
>>
>> Thanks,
>> srini
>>
>>>
>>> Thanks for the review,
>>> Maxime
>>>
>>>>>
>>
> 
> 

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