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Date: Mon, 17 Aug 2026 02:15:49 +0100
From: Jonathan Cameron <jic23@kernel.org>
To: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Matti Vaittinen <mazziesaccount@gmail.com>, Matti Vaittinen
 <matti.vaittinen@fi.rohmeurope.com>, Matti Vaittinen
 <matti.vaittinen@linux.dev>, David Lechner <dlechner@baylibre.com>, Nuno
 =?UTF-8?B?U8Oh?= <nuno.sa@analog.com>, Andy Shevchenko <andy@kernel.org>,
 Javier Carrasco <javier.carrasco.cruz@gmail.com>, Mehdi Djait
 <mehdi.djait.k@gmail.com>, linux-iio@vger.kernel.org,
 linux-kernel@vger.kernel.org, Kalle Niemi <kaleposti@gmail.com>, Topi
 =?UTF-8?B?U29ua2Fqw6Rydmk=?= <sonkajarvi@hotmail.com>
Subject: Re: [PATCH 07/12] iio: pressure: rohm-bm1390: Fix AVE_NUM
 initialization
Message-ID: <20260817021549.29522111@jic23-huawei>
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On Tue, 11 Aug 2026 13:08:14 +0300
Andy Shevchenko <andriy.shevchenko@intel.com> wrote:

> On Tue, Aug 11, 2026 at 12:05:47PM +0300, Matti Vaittinen wrote:
> > On 10/08/2026 23:06, Andy Shevchenko wrote:  
> > > On Mon, Aug 10, 2026 at 10:53:07AM +0300, Matti Vaittinen wrote:  
> 
> ...
> 
> > > > Use FIELD_PREP() to shift the intended AVE_NUM value to correct field.  
> > > 
> > > Can it be FIELD_PREP_CONST()?  
> > 
> > Can you please elaborate why it should in this case?  
> 
> I'm not sure why it's not obvious, but the parameters are constants, why would
> we need an additional check or even checks?
> 
Hmm.  I went and had a look as this macro turns up a fair bit.
I'm fairly sure in the case of a pair of compile time constants
FIELD_PREP() both performs additional checks at compile time and
probably collapses to a constant.
The docs for FIELD_PREP_CONST() observe it is for when
you need it to be a constant rather than when it might be
(even if you know it is)

So I think it's not necessarily appropriate here.