linux-kernel - Re: [PATCH RFC v2] mac80211: debugfs option to force TX status frames

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Message-ID: <20190320121320.myrxmtfccaoybyih@azazel.net>
Date:   Wed, 20 Mar 2019 12:13:20 +0000
From:   Jeremy Sowden <jeremy@...zel.net>
To:     Julius Niedworok <julius.n@....net>
Cc:     Kalle Valo <kvalo@...eaurora.org>, ga58taw@...um.de,
        linux-wireless@...r.kernel.org, david@...hat.com, nc@....in.tum.de,
        Johannes Berg <johannes@...solutions.net>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2] mac80211: debugfs option to force TX status frames

On 2019-03-19, at 16:07:32 +0100, Julius Niedworok wrote:
> On 11.03.2019 15:52, Jeremy Sowden wrote:
> > It's the value that matters, not the type.  It will only be too big
> > for the buffer if the result of casting local->force_tx_status to
> > int is less than -9 or greeater than 99.
> >
> >  scnprintf(buf, size(buf), "%lld\n",
> >            (long long)local->force_tx_status)
> >
> > would also be fine if the value were in range.  Note also that
> > scnprintf will not overrun the buffer: it will truncate the string.
>
> Thanks for the clarification :)

You're welcome. :)

> > As it happens, arguments to variadic functions are subject to the
> > "default argument promotions," so if local->force_tx_status is in
> > fact a bool (I can't find the definition), it would be promoted to
> > int and the cast is superfluous.
>
> Yes - the cast is superfluous. We still think it might be useful to
> keep it there to make the point that the value will be casted.
> However, if you prefer to omit the cast, we are happy to take it out.

If I were maintaining this code, I'd probably take it out.  However, I
did have to check the documentation to verify that the cast wasn't
required, and I know the more obscure corners of the C standard pretty
well, so it may cause less confusion to keep it.

J.

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