[BusyBox] Re: [BusyBox-cvs] busybox/util-linux hwclock.c,1.3,1.4

[Robert Griebl]

On Thursday 02 January 2003 08:33, Erik Andersen wrote:
> On Thu Jan 02, 2003 at 12:16:57AM -0700, Robert Griebl wrote:
> > Doing this wrong should be punished even harder :)
> >  - Robert
> >
> >
> > +#define RTC_SET_TIME   _IOW('p', 0x0a, struct linux_rtc_time) /* Set RTC
> > time    */ +#define RTC_RD_TIME    _IOR('p', 0x09, struct linux_rtc_time)
> > /* Read RTC time   */
>
> Interesting.  The structs are identical up to the sizeof(struct
> linux_rtc_time).  At least for x86, the kernel copy_from_user and
> copy_to_user simply ignore the surplus tm_gmtoff, tm_zone, etc
> fields.  I guess the powerpc version tries to worry about the
> extra fields and complains.  I had initially added that struct
> but decided it was unnecessary.  Guess I was wrong...
>

#define _IOR(type,nr,size)  _IOC(_IOC_READ,(type),(nr),sizeof(size))

I think the problem is that the size of the argument is coded into the ioctl 
number.

cu
Robert

-- 
_____________________________________________
Robert 'sandman' Griebl
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