linux-kernel - Re: [V2 2/6] driver core: auxiliary bus: Add driver data helpers

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Message-ID: <YbB3TbU5dfPse9LU@google.com>
Date:   Wed, 8 Dec 2021 09:13:49 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Leon Romanovsky <leon@...nel.org>,
        "David E. Box" <david.e.box@...ux.intel.com>, hdegoede@...hat.com,
        bhelgaas@...gle.com, andriy.shevchenko@...ux.intel.com,
        srinivas.pandruvada@...el.com, shuah@...nel.org,
        mgross@...ux.intel.com, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [V2 2/6] driver core: auxiliary bus: Add driver data helpers

On Wed, 08 Dec 2021, Greg KH wrote:

> On Wed, Dec 08, 2021 at 08:43:53AM +0000, Lee Jones wrote:
> > On Wed, 08 Dec 2021, Greg KH wrote:
> > 
> > > On Wed, Dec 08, 2021 at 09:03:16AM +0200, Leon Romanovsky wrote:
> > > > On Tue, Dec 07, 2021 at 09:14:44AM -0800, David E. Box wrote:
> > > > > Adds get/set driver data helpers for auxiliary devices.
> > > > > 
> > > > > Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
> > > > > Reviewed-by: Mark Gross <markgross@...nel.org>
> > > > > ---
> > > > > V2
> > > > >   - No changes
> > > > > 
> > > > >  include/linux/auxiliary_bus.h | 10 ++++++++++
> > > > >  1 file changed, 10 insertions(+)
> > > > 
> > > > I would really like to see an explanation why such obfuscation is really
> > > > needed. dev_*_drvdata() is a standard way to access driver data.
> > 
> > I wouldn't call it obfuscation, but it does looks like abstraction for
> > the sake of abstraction, which I usually push back on.  What are the
> > technical benefits over using the dev_*() variant?
> 
> See my response at:
> 	https://lore.kernel.org/r/YbBwOb6JvWkT3JWI@kroah.com
> for why it is a good thing to do.

I saw this after I'd sent my query.

> In short, driver authors should not have to worry about mixing
> bus-specific and low-level driver core functions.

Okay, that makes sense.

I guess my view abstraction for the sake of it is slightly higher
level as I vehemently dislike it when driver-set writers create their
own APIs, such as; (just off the top of my head, not a real example)
cros_get_data() or cros_write() which are usually abstractions of top
level APIs like platform_get_data() and regmap_write() respectively.

Abstracting at *real* API level does seem like the right thing to do.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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