linux-kernel - Re: [PATCH 08/16] i2c: core: Introduce i2c_get_adapter

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Message-ID: <20250408162900.41b6bc08@bootlin.com>
Date: Tue, 8 Apr 2025 16:29:00 +0200
From: Herve Codina <herve.codina@...tlin.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>, Shawn Guo
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 Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 08/16] i2c: core: Introduce i2c_get_adapter_supplier()

On Tue, 8 Apr 2025 16:47:51 +0300
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> On Tue, Apr 08, 2025 at 03:08:36PM +0200, Herve Codina wrote:
> > On Mon, 7 Apr 2025 18:27:07 +0300
> > Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:  
> > > On Mon, Apr 07, 2025 at 04:55:37PM +0200, Herve Codina wrote:  
> 
> ...
> 
> > > > +	return get_device(adapter->supplier ?: adapter->dev.parent);    
> > > 
> > > What will be the meaning when both are set? Why dev.parent is not the same
> > > as supplier in this case?  Looking at the commit message example, it seems
> > > like you want to provide a physdev or sysdev (as term supplier seems more
> > > devlink:ish), like it's done elsewhere. And in the same way _always_ initialise
> > > it. In such a case, the ambiguity will be gone.  
> > 
> > When both are set (this is case for i2c muxes), the adapter->supplier the
> > device that register the I2C adapter using i2c_add_adapter() or variant.
> > In other word, the device that creates the I2C adapter.
> > 
> > The adapter->dev.parent is most of the time the device that register the
> > I2C adapter except for i2c muxes. For I2C muxes, this adapter->dev.parent
> > is the adapter the i2c mux is connected to.
> > 
> > Between physdev and sysdev, I really prefer physdev and, if renaming from
> > supplier to physdev is still needed (and wanted), I will rename it. Let me
> > know.  
> 
> The terms supplier/consumer are widely used in terms of power and devlink.
> I think here should not be used the term supplier.

physdev seems good.
I will use that.

> 
> > For initialization, I don't want to modify all the I2C controller drivers.
> > What I can do is to initialize adapter->supplier using adapter->dev.parent
> > during the i2c_register_adapter() call if it was not already initialize by
> > the caller (i.e. the I2C controller driver).  
> 
> This can be done in the I²C core, but I'm not insisting on this part.
> We can start from your function only and then decide later on how to
> proceed (depending on how many users of that field appear and what
> they want to do with it).
> 

Right I think I can keep my function as it.

Wolfram any opinion?

Best regards,
Hervé