Re: [PATCH -mm 1/3] swsusp: Add ioctl for swap files support

From: Arnd Bergmann
Date: Sat Sep 30 2006 - 16:37:40 EST

Am Saturday 30 September 2006 21:58 schrieb Rafael J. Wysocki:
> > Your definition looks wrong, '_IOW(SNAPSHOT_IOC_MAGIC, 13, void *)' means
> > your ioctl passes a pointer to a 'void *'.
> >
> > You probably mean
> >
> >                                               struct resume_swap_area)
> No.  I mean the ioctl passes a pointer, the size of which is sizeof(void *).

That's a very bad thing to do. It means that the ioctl number is different
between 32 and 64 bit and you need to write a conversion handler that
first reads your pointer and then then writes the real data.

Also, it needs to be at least _IOR() in the case you're describing,
because the pointer is read, not written (I hope).

Arnd <><
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