RE: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API

From: Biju Das <biju.das.jz@bp.renesas.com>
To: Wolfram Sang <wsa@kernel.org>, Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Andrzej Hajda" <andrzej.hajda@intel.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Robert Foss" <rfoss@kernel.org>,
	"David Airlie" <airlied@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Kieran Bingham" <kieran.bingham@ideasonboard.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Hans Verkuil" <hverkuil-cisco@xs4all.nl>,
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	"Jonas Karlman" <jonas@kwiboo.se>,
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	"Marek Behún" <kabel@kernel.org>,
	"Jiasheng Jiang" <jiasheng@iscas.ac.cn>,
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	"Ahmad Fatoum" <a.fatoum@pengutronix.de>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
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	"Fabrizio Castro" <fabrizio.castro.jz@renesas.com>,
	"linux-renesas-soc@vger.kernel.org"
	<linux-renesas-soc@vger.kernel.org>,
	"Mark Brown" <broonie@kernel.org>
Subject: RE: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
Date: Tue, 13 Jun 2023 17:57:55 +0000	[thread overview]
Message-ID: <OS0PR01MB592210CE54A9CF953980DFEE8655A@OS0PR01MB5922.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <OS0PR01MB592220CCA081848A711D75328655A@OS0PR01MB5922.jpnprd01.prod.outlook.com>

Hi Wolfram,

Thanks for the feedback.

> Subject: RE: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
> 
> Hi Wolfram,
> 
> Thanks for the feedback.
> 
> > Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device
> > API
> >
> > Hi everyone,
> >
> > > Perhaps we should first think through what an ancillary device
> > > really is.  My understanding is that it is used to talk to secondary
> > > addresses of a multi-address I2C slave device.
> >
> > As I mentioned somewhere before, this is not the case. Ancillary
> > devices are when one *driver* handles more than one address.
> > Everything else has been handled differently in the past (for  all the
> uses I am aware of).
> >
> > Yet, I have another idea which is so simple that I wonder if it maybe
> > has already been discussed so far?
> >
> > * have two regs in the bindings
> 
> OK, it is inline with DT maintainers expectation as it is matching with
> real hw as single device node having two regs.
> 
> > * use the second reg with i2c_new_client_device to instantiate the
> >   RTC sibling. 'struct i2c_board_info', which is one parameter, should
> >   have enough options to pass data, e.g it has a software_node.
> 
> OK, I can see the below can be passed from PMIC to new client device.
> 
> 	client->addr = info->addr;
> 
> 	client->init_irq = info->irq;
> 
> >
> > Should work or did I miss something here?
> 
> I guess it will work. We instantiate appropriate device based On PMIC
> revision and slave address and IRQ resource passed through 'struct
> i2c_board_info'
> 
> Will check this and update you.

info.irq = irq; -->Irq fine
info.addr = addr; -->slave address fine
size = strscpy(info.type, name, sizeof(info.type)); -->instantiation based on PMIC version fine.

1) How do we share clk details on instantiated device to find is it connected to external crystal or external clock source? as we cannot pass of_node between PMIC and "i2c_board_info" as it results in pinctrl failure. info->platformdata and
Client->dev.platformdata to retrieve this info??

Cheers,
Biju