linux-kernel - Re: [PATCH 1/5] ARM: findbit: document ARMv5 bit offset calculation

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Message-ID: <CAHk-=wi5Ud30Od-=buKvrvinemR7uVuTUkbKqCGu_ySZPjLVfA@mail.gmail.com>
Date:   Fri, 28 Oct 2022 12:10:16 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Yury Norov <yury.norov@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/5] ARM: findbit: document ARMv5 bit offset calculation

On Fri, Oct 28, 2022 at 12:01 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> In contrast, the arm code doesn't do the "min()" at all, and if there
> are bits after the bitmap (in a partial byte), it will just return
> those bits.

No, I did misread the code. It returns 'size' for the no bits case,
and the 'movlo r0, r1'; does the right thing for the "bits past the
end" case too.

I guess I need to get better at reading arm asm.

                Linus