linux-kernel - Re: [PATCH v4] mfd: core: Support auxiliary device

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Message-ID: <2025051221-gulf-schematic-26e1@gregkh>
Date: Mon, 12 May 2025 12:36:24 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Raag Jadav <raag.jadav@...el.com>
Cc: Lee Jones <lee@...nel.org>, david.m.ertman@...el.com,
	ira.weiny@...el.com, andriy.shevchenko@...ux.intel.com,
	mika.westerberg@...ux.intel.com, heikki.krogerus@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mfd: core: Support auxiliary device

On Mon, May 12, 2025 at 01:22:41PM +0300, Raag Jadav wrote:
> On Sat, May 03, 2025 at 01:01:23AM +0300, Raag Jadav wrote:
> > On Thu, May 01, 2025 at 01:50:28PM +0100, Lee Jones wrote:
> > > On Mon, 28 Apr 2025, Raag Jadav wrote:
> > > 
> > > > Extend MFD subsystem to support auxiliary child device. This is useful
> > > > for MFD usecases where parent device is on a discoverable bus and doesn't
> > > > fit into the platform device criteria. Purpose of this implementation is
> > > > to provide discoverable MFDs just enough infrastructure to register
> > > > independent child devices without abusing the platform device.
> > > > 
> > > > Current support is limited to just PCI type MFDs, but this can be further
> > > > extended to support other types like USB in the future.
> > > > 
> > > > Signed-off-by: Raag Jadav <raag.jadav@...el.com>
> > > > ---
> > > > 
> > > > v2: Introduce a shared struct mfd_aux_device
> > > >     Introduce auxiliary device opt-in flag
> > > > 
> > > > v3: Fix device_type ABI breakage (Andy)
> > > >     Aesthetic adjustments (Andy)
> > > > 
> > > > v4: s/mfd_aux/maux
> > > >     Allow num_resources for child device (Andy)
> > > >     Fix build warning (Andy)
> > > > 
> > > >  drivers/mfd/Kconfig      |   2 +-
> > > >  drivers/mfd/Makefile     |   2 +-
> > > >  drivers/mfd/mfd-aux.c    | 156 +++++++++++++++++++++++++++++++
> > > 
> > > This looks like mostly duplicated platform device code.
> > > 
> > > If you are _certain_ that it needs to exist, you need to push it out to
> > > the auxiliary subsystem and remove any traces of it being MFD related.
> > > 
> > > If it's needed by MFD, it'll be needed by other auxiliary users.  Even
> > > if not now, sometime in the future.
> > 
> > Greg, if you are okay with this, please let me know. Or perhaps suggest
> > a better alternative.
> 
> Greg, any guidance on this?

I don't know what to say, I don't see the code here that is being
quoted, sorry.  If this should be in the aux code, add it and submit a
patch that uses it so we can see what you are referring to.

confused,

greg k-h