Re: [PATCH 01/17] bitfield: Add non-constant field_{prep,get}() helpers

From: Johannes Berg <johannes@sipsolutions.net>
To: Geert Uytterhoeven <geert@linux-m68k.org>,
	Jakub Kicinski <kuba@kernel.org>
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Subject: Re: [PATCH 01/17] bitfield: Add non-constant field_{prep,get}() helpers
Date: Tue, 23 Nov 2021 17:24:15 +0100	[thread overview]
Message-ID: <637a4183861a1f2cdab52b7652bfa7ed33fbcdd2.camel@sipsolutions.net> (raw)
In-Reply-To: <CAMuHMdWAAGrQUZN18cnDTDUUhuPNTZTFkRMe2Sbf+s7CedPSxA@mail.gmail.com>

On Tue, 2021-11-23 at 09:36 +0100, Geert Uytterhoeven wrote:

Ah, here's your comment wrt. which one is nicer :)

> > > We have the upper-case (constant) versions, and already
> > > {u32,...}_get_bits()/etc.
> 
> TBH, I don't like the *_get_bits() API: in general, u32_get_bits() does
> the same as FIELD_GET(), but the order of the parameters is different?

I don't really see how "the order of parameters is different" is a
downside? Yeah it means if you're used to FIELD_GET() then you'll
retrain, but ...?

> (*_replace_bits() seems to be useful, though)

Indeed.

Also as I said in my other mail, the le32/be32/... variants are
tremendously useful, and they fundamentally cannot be expressed with the
FIELD_GET() or field_get() macros. IMHO this is a clear advantage to the
typed versions, and if you ask me we should get rid of the FIELD_GETand
FIELD_PREP entirely - difficult now, but at least let's not propagate
that?

johannes