linux-kernel - Re: [PATCH 01/17] bitfield: Add non-constant field

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMuHMdXwhO30gy42tfGSsEgJAjDOAkQ_cUXMMiSBjMsUj0nqaA@mail.gmail.com>
Date:   Tue, 23 Nov 2021 17:31:54 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Tony Lindgren <tony@...mide.com>,
        Russell King <linux@...linux.org.uk>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Paul Walmsley <paul@...an.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Tero Kristo <kristo@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Lorenzo Bianconi <lorenzo.bianconi83@...il.com>,
        Benoit Parrot <bparrot@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andrew Jeffery <andrew@...id.au>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Joel Stanley <joel@....id.au>,
        Ping-Ke Shih <pkshih@...ltek.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Magnus Damm <magnus.damm@...il.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Keerthy <j-keerthy@...com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:TI ETHERNET SWITCH DRIVER (CPSW)" 
        <linux-omap@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-iio@...r.kernel.org,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux MMC List <linux-mmc@...r.kernel.org>,
        linux-aspeed@...ts.ozlabs.org, openbmc@...ts.ozlabs.org,
        linux-wireless <linux-wireless@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        ALSA Development Mailing List <alsa-devel@...a-project.org>
Subject: Re: [PATCH 01/17] bitfield: Add non-constant field_{prep,get}() helpers

Hi Johannes,

On Tue, Nov 23, 2021 at 5:21 PM Johannes Berg <johannes@...solutions.net> wrote:
> On Tue, 2021-11-23 at 09:30 +0100, Geert Uytterhoeven wrote:
> > > We have the upper-case (constant) versions, and already
> > > {u32,...}_get_bits()/etc.
> >
> > These don't work for non-const masks.
>
> Obviously, I know that. Still, just saying.
>
> I'm actually in the opposite camp to you I guess - I much prefer the
> typed versions (u32_get_bits() and friends) over the FIELD_GET() macros
> that are more magic.
>
> Mostly though that's because the typed ones also have le32_/be32_/...
> variants, which are tremendously useful, and so I prefer to use them all
> across. In fact, I have considered in the past to just remove the upper-
> case macros entirely but ... no time I guess.

OK, I have to think a bit about this.
FTR, initially I didn't like the FIELD_{GET,PREP}() macros neither ;-)

> In fact, you have e.g. code in drivers/usb/chipidea/udc.c that does
> things like cpu_to_le32(mul << __ffs(...)) - though in those cases it's
> actually constant today, so you could already write it as
> le32_encode_bits(...).

Yeah, there are lots of opportunities for improvement for
drivers/usb/chipidea/.  I didn't include a conversion patch for that
driver, as it led me too deep into the rabbit hole, and I wanted to
get something posted rather sooner than later...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds