linux-kernel - Re: [PATCH v3 01/10] Add auxiliary bus support

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Date:   Thu, 5 Nov 2020 14:00:00 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Ertman, David M" <david.m.ertman@...el.com>
Cc:     "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        Takashi Iwai <tiwai@...e.de>, Mark Brown <broonie@...nel.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        Doug Ledford <dledford@...hat.com>,
        Netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Fred Oh <fred.oh@...ux.intel.com>,
        Parav Pandit <parav@...lanox.com>,
        "Saleem, Shiraz" <shiraz.saleem@...el.com>,
        "Patil, Kiran" <kiran.patil@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Leon Romanovsky <leonro@...dia.com>
Subject: Re: [PATCH v3 01/10] Add auxiliary bus support

On Thu, Nov 5, 2020 at 11:28 AM Ertman, David M
<david.m.ertman@...el.com> wrote:
[..]
> > > Each auxiliary_device represents a part of its parent
> > > +functionality. The generic behavior can be extended and specialized as
> > needed
> > > +by encapsulating an auxiliary_device within other domain-specific
> > structures and
> > > +the use of .ops callbacks. Devices on the auxiliary bus do not share any
> > > +structures and the use of a communication channel with the parent is
> > > +domain-specific.
> >
> > Should there be any guidance here on when to use ops and when to just
> > export functions from parent driver to child. EXPORT_SYMBOL_NS() seems
> > a perfect fit for publishing shared routines between parent and child.
> >
>
> I would leave this up the driver writers to determine what is best for them.

I think there is a pathological case that can be avoided with a
statement like the following:

"Note that ops are intended as a way to augment instance behavior
within a class of auxiliary devices, it is not the mechanism for
exporting common infrastructure from the parent. Consider
EXPORT_SYMBOL_NS() to convey infrastructure from the parent module to
the auxiliary module(s)."

As for your other dispositions of the feedback, looks good to me.