linux-kernel - Re: [PATCH 0/9] bitfield: tidy up bitfield.h

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Message-ID: <20251209094433.768a76ae@pumpkin>
Date: Tue, 9 Dec 2025 09:44:33 +0000
From: David Laight <david.laight.linux@...il.com>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: Yury Norov <yury.norov@...il.com>, Rasmus Villemoes
 <linux@...musvillemoes.dk>, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org, Geert Uytterhoeven <geert+renesas@...der.be>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>, Jonathan Cameron
 <Jonathan.Cameron@...wei.com>, Crt Mori <cmo@...exis.com>, Richard Genoud
 <richard.genoud@...tlin.com>, Andy Shevchenko
 <andriy.shevchenko@...el.com>, Luo Jie <quic_luoj@...cinc.com>, Peter
 Zijlstra <peterz@...radead.org>, Jakub Kicinski <kuba@...nel.org>,
 netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>, Simon
 Horman <simon.horman@...ronome.com>, Andreas Noever
 <andreas.noever@...il.com>, Yehezkel Bernat <YehezkelShB@...il.com>
Subject: Re: [PATCH 0/9] bitfield: tidy up bitfield.h

On Tue, 9 Dec 2025 08:08:06 +0100
Mika Westerberg <mika.westerberg@...ux.intel.com> wrote:

> Hi David,
> 
> On Mon, Dec 08, 2025 at 10:42:41PM +0000, david.laight.linux@...il.com wrote:
> > From: David Laight <david.laight.linux@...il.com>
> > 
> > I noticed some very long (18KB) error messages from the compiler.
> > Turned out they were errors on lines that passed GENMASK() to FIELD_PREP().
> > Since most of the #defines are already statement functions the values
> > can be copied to locals so the actual parameters only get expanded once.
> > 
> > The 'bloat' is reduced further by using a simple test to ensure 'reg'
> > is large enough, slightly simplifying the test for constant 'val' and
> > only checking 'reg' and 'val' when the parameters are present.
> > 
> > The first two patches are slightly problematic.
> > 
> > drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c manages to use
> > a #define that should be an internal to bitfield.h, the changed file
> > is actually more similar to the previous version.
> > 
> > drivers/thunderbolt/tb.h passes a bifield to FIELD_GET(), these can't
> > be used with sizeof or __auto_type. The usual solution is to add zero,
> > but that can't be done in FIELD_GET() because it doesn't want the value
> > promoted to 'int' (no idea how _Generic() treated it.)
> > The fix is just to add zero at the call site.
> > (The bitfield seems to be in a structure rad from hardware - no idea
> > how that works on BE (or any LE that uses an unusual order for bitfields.)  
> 
> Okay but can you CC me the actual patch too? I only got the cover letter
> ;-)

Ah, sorry I'd changed the git settings..
I'll resend it all.

	David