On Friday 17 July 2015 14:37:41 Mark Brown wrote:
> On Fri, Jul 17, 2015 at 03:26:38PM +0200, Arnd Bergmann wrote:
>
> > I think we will have to provide a macro from user space that tells
> > the UAPI headers what the size of time_t is. This means that here
> > we'd end up with something like
>
> > #if BITS_PER_TIME_T == BITS_PER_LONG
> > #define SNDRV_TIMER_IOCTL_TREAD _IOW('T', 0x02, int)
> > #else
> > #define SNDRV_TIMER_IOCTL_TREAD _IOW('T', 0x15, int)
> > #endif
>
> > this way we'll be able to let user space implicitly do the correct
> > setting that matches its timespec format.
>
> Yeah, that was where my thinking was going. You should then be able to
> make the else case expose a 32 bit version under a different name so
> applications that really wanted to be able to do fallback on old kernels
> could do so but the default would DTRT.
I'm unsure if that would actually help anybody: The new version would
only be seen for applications that are built with a 64-bit time_t,
and that requires a new kernel for a number of reasons. It might
help bridge the window between kernels that have support for basic
syscalls but not a particular ioctl like this one, but approach so
far was that I'd just treat that case as a bug and tell people to
not expect 64-bit time_t in user space to work in all cases until
we have a kernel that has all drivers converted.
Arnd
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