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Subject: Re: [PATCH] [RESEND] floppy: fix harmless clang build warning
To:     Arnd Bergmann <arnd@arndb.de>, Jiri Kosina <jikos@kernel.org>
Cc:     Robert Elliott <elliott@hpe.com>, Keith Busch <kbusch@kernel.org>,
        Hannes Reinecke <hare@suse.de>, Omar Sandoval <osandov@fb.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Andy Whitcroft <apw@canonical.com>,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190619131959.2055400-1-arnd@arndb.de>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <649b433f-9a6b-a8a8-65ea-aa15a6296246@kernel.dk>
Date:   Thu, 20 Jun 2019 01:36:43 -0600
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On 6/19/19 7:19 AM, Arnd Bergmann wrote:
> clang warns about unusual code in floppy.c that looks like it
> was intended to be a bit mask operation, checking for a specific
> bit in the UDP->cmos variable (FLOPPY1_TYPE expands to '4' on
> ARM):
> 
> drivers/block/floppy.c:3902:17: error: use of logical '&&' with constant operand [-Werror,-Wconstant-logical-operand]
>          if (!UDP->cmos && FLOPPY1_TYPE)
>                         ^  ~~~~~~~~~~~~
> drivers/block/floppy.c:3902:17: note: use '&' for a bitwise operation
>          if (!UDP->cmos && FLOPPY1_TYPE)
> 
> The check here is redundant anyway, if FLOPPY1_TYPE is zero, then
> assigning it to a zero UDP->cmos field does not change anything,
> so removing the extra check here has no effect other than shutting
> up the warning.
> 
> On x86, this will no longer read a hardware register, as the
> FLOPPY1_TYPE macro is not expanded if UDP->cmos is already
> zero, but the result is the same.

Applied, thanks.

-- 
Jens Axboe