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

From: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
To: Luca Ceresoli <luca.ceresoli@bootlin.com>,
	Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Wolfram Sang" <wsa@kernel.org>,
	"Matti Vaittinen" <Matti.Vaittinen@fi.rohmeurope.com>,
	"Laurent Pinchart" <laurent.pinchart+renesas@ideasonboard.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Peter Rosin" <peda@axentia.se>,
	"Liam Girdwood" <lgirdwood@gmail.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Sakari Ailus" <sakari.ailus@linux.intel.com>,
	"Michael Tretter" <m.tretter@pengutronix.de>,
	"Shawn Tu" <shawnx.tu@intel.com>,
	"Hans Verkuil" <hverkuil@xs4all.nl>,
	"Mike Pagano" <mpagano@gentoo.org>,
	"Krzysztof Hałasa" <khalasa@piap.pl>,
	"Marek Vasut" <marex@denx.de>,
	"Luca Ceresoli" <luca@lucaceresoli.net>
Subject: Re: [PATCH v7 1/7] i2c: add I2C Address Translator (ATR) support
Date: Thu, 19 Jan 2023 12:09:57 +0200	[thread overview]
Message-ID: <db2e7386-e625-5bad-0c99-bae633e96d80@ideasonboard.com> (raw)
In-Reply-To: <20230119092115.02cbbab3@booty>

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