linux-kernel - Re: [PATCH v7 1/7] i2c: add I2C Address Translator (ATR) support

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Message-ID: <db2e7386-e625-5bad-0c99-bae633e96d80@ideasonboard.com>
Date:   Thu, 19 Jan 2023 12:09:57 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Luca Ceresoli <luca.ceresoli@...tlin.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Wolfram Sang <wsa@...nel.org>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.com>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Peter Rosin <peda@...ntia.se>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Michael Tretter <m.tretter@...gutronix.de>,
        Shawn Tu <shawnx.tu@...el.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Mike Pagano <mpagano@...too.org>,
        Krzysztof Hałasa <khalasa@...p.pl>,
        Marek Vasut <marex@...x.de>,
        Luca Ceresoli <luca@...aceresoli.net>
Subject: Re: [PATCH v7 1/7] i2c: add I2C Address Translator (ATR) support

On 19/01/2023 10:21, Luca Ceresoli wrote:

<snip>

>>>>> +void i2c_atr_set_driver_data(struct i2c_atr *atr, void *data)
>>>>> +{
>>>>> +	atr->priv = data;
>>>>> +}
>>>>> +EXPORT_SYMBOL_NS_GPL(i2c_atr_set_driver_data, I2C_ATR);
>>>>> +
>>>>> +void *i2c_atr_get_driver_data(struct i2c_atr *atr)
>>>>> +{
>>>>> +	return atr->priv;
>>>>> +}
>>>>> +EXPORT_SYMBOL_NS_GPL(i2c_atr_get_driver_data, I2C_ATR);
>>>>
>>>> Just to be sure: Is it really _driver_ data and not _device instance_ data?
>>>
>>> It is device instance data indeed. I don't remember why this got
>>> changed, but in v3 it was i2c_atr_set_clientdata().
>>
>> It's me who was and is against calling it clientdata due to possible
>> confusion with i2c_set/get_clientdata() that is about *driver data*.
>> I missed that time the fact that this is about device instance data.
>> I dunno which name would be better in this case, i2c_atr_set/get_client_priv() ?
> 
> Not sure I'm following you here. The i2c_atr_set_clientdata() name was
> given for similarity with i2c_set_clientdata(). The latter wraps
> dev_set_drvdata(), which sets `struct device`->driver_data. There is
> one driver_data per each `struct device` instance, not per each driver.
> The same goes for i2c_atr_set_driver_data(): there is one priv pointer
> per each `struct i2c_atr` instance.

I'm a bit confused. What is "driver data" and what is "device instance 
data"?

This deals with the driver's private data, where the "driver" is the 
owner/creator of the i2c-atr. The i2c-atr itself doesn't have a device 
(it's kind of part of the owner's device), and there's no driver in 
i2c-atr.c

I don't like "client" here, as it reminds me of i2c_client (especially 
as we're in i2c context).

What about i2c_atr_set_user_data()? Or "owner_data"?

  Tomi