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From: Rasmus Villemoes <>
To: "" <>
Subject: watchdog ioctl inconsistencies
Date: Mon, 26 Aug 2019 14:54:31 +0200
Message-ID: <> (raw)


uapi/linux/watchdog.h has these


This is a write from userspace perspective, so should have been _IOW.


This one doesn't actually take an argument, so should just have been an
_IO - or if anything, an _IOW. One could be misled to think that if the
int argument has 'V' somewhere (perhaps first or last byte, depending on
endianness) that would count as a magic close.


The SETTIMEOUT handling does fall through to the GETTIMEOUT case, so
that one is indeed a "write this, but tell me what value actually took
effect". The SETPRETIMEOUT case ends with a break, so that one is really

There's not much to do about these, I think, but perhaps one could add a
comment to the uapi header containing the magic explains-all phrase
"historical reasons".

Does any static checker actually know about these conventions and peek
inside the _IO*() macros when used as an argument to ioctl(), comparing
the type and constness of the third argument to the direction/type
implied by the macro?


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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-26 12:54 Rasmus Villemoes [this message]
2019-08-27  0:19 ` Guenter Roeck

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