From: Arnd Bergmann <arnd@arndb.de>
To: "Michał Mirosław" <mirqus@gmail.com>
Cc: John Calixto <john.calixto@modsystems.com>,
linux-mmc@vger.kernel.org, Chris Ball <cjb@laptop.org>,
Andrei Warkentin <andreiw@motorola.com>
Subject: Re: [PATCH v4] mmc: Add ioctl to let userspace apps send ACMDs
Date: Wed, 13 Apr 2011 01:00:39 +0200 [thread overview]
Message-ID: <201104130100.39810.arnd@arndb.de> (raw)
In-Reply-To: <BANLkTimn3vB1JaBfboOL0ayG2FpXsUMe7w@mail.gmail.com>
On Tuesday 12 April 2011, Michał Mirosław wrote:
> > + unsigned int cmd_timeout_ms;
> > + __u64 data_ptr; /* DAT buffer */
>
> This will be more natural if you have an anonymous union here:
> union {
> __u64 data_ptr_
> void *data_ptr;
> };
No, that really does not work. It's important for all members of the ioctl data
structure to have a fixed size, independent of the size of long or pointer.
If you do a union, the pointer ends up in the first 32 bits of the 64 bit member,
which does not work on big-endian architectures. It also doesn't work on 31
bit architectures, although that is a minor worry here.
Arnd
next prev parent reply other threads:[~2011-04-12 23:00 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-11 21:47 mmc: Add ioctl to let userspace apps send ACMDs John Calixto
2011-04-11 21:55 ` [PATCH v4] " John Calixto
2011-04-12 14:21 ` Michał Mirosław
2011-04-12 21:51 ` John Calixto
2011-04-12 23:00 ` Arnd Bergmann [this message]
2011-04-12 23:08 ` John Calixto
2011-04-18 14:39 ` Arnd Bergmann
2011-04-18 16:30 ` John Calixto
2011-04-12 23:10 ` Arnd Bergmann
2011-04-12 23:40 ` John Calixto
2011-04-18 14:42 ` Arnd Bergmann
2011-04-18 16:37 ` John Calixto
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