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Message-ID: <546e2ab5-f520-c85e-d6f4-ca7b02457d4c@rasmusvillemoes.dk>
Date:   Mon, 12 Jun 2023 13:08:04 +0200
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Subject: Re: [PATCH v3 3/4] vsscanf(): do not skip spaces
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To:     Demi Marie Obenour <demi@invisiblethingslab.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
        Lee Jones <lee@kernel.org>, Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     linux-media@vger.kernel.org, linux-staging@lists.linux.dev,
        linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org,
        Christoph Hellwig <hch@lst.de>
References: <20230610204044.3653-1-demi@invisiblethingslab.com>
 <20230610204044.3653-4-demi@invisiblethingslab.com>
From:   Rasmus Villemoes <linux@rasmusvillemoes.dk>
In-Reply-To: <20230610204044.3653-4-demi@invisiblethingslab.com>
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On 10/06/2023 22.40, Demi Marie Obenour wrote:
> Passing spaces before e.g. an integer is usually
> not intended. 

Maybe, maybe not. But it's mandated by POSIX/C99.

And of course we are free to ignore that and implement our own semantics
(though within the constraints that we really want -Wformat to help us),
but there seems to be existing code in-tree that relies on this
behavior. For example I think this will break
fsl_sata_intr_coalescing_store() which uses a scanf format of "%u%u".

Sure, that could just say "%u %u" instead, but the point is that
currently it doesn't. So without some reasonably thorough analysis
across the tree, and updates of affected callers, NAK.

Rasmus