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References: <20210603125841.27436-1-wsa+renesas@sang-engineering.com>
In-Reply-To: <20210603125841.27436-1-wsa+renesas@sang-engineering.com>
From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 3 Jun 2021 15:27:04 +0200
Message-ID: <CAMuHMdVLzzK-hsaEO4mEkOeCnzKuXgORanB+GGnHZjonwQAD9w@mail.gmail.com>
Subject: Re: [PATCH] docs: fault-injection: fix non-working usage of negative values
To:     Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        Akinobu Mita <akinobu.mita@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
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Hi Wolfram,

On Thu, Jun 3, 2021 at 2:59 PM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
> Fault injection uses debugfs in a way that the provided values via sysfs
> are interpreted as u64. Providing negative numbers results in an error:
>
> /sys/kernel/debug/fail_function# echo -1 > times
> sh: write error: Invalid argument

Interesting...

> Update the docs and examples to use "printf %#x <val>" in these cases.
> For "retval", reword the paragraph a little and fix a typo.

Presumably this is something that used to work, but was broken (not
so) recently.  Perhaps the code should be fixed instead?

The code uses debugfs_create_atomic_t(), and atomic_t is signed, so
I'd expect negative numbers to work.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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