Re: [RFC v3 1/2] v4l: Do not use enums in IOCTL structs

[Andy Walls <awalls@xxxxxxxxxxxxxxxx>]

On Wed, 2012-05-02 at 19:17 -0300, Mauro Carvalho Chehab wrote:

> We can speed-up the conversions, with something like:
> 
> enum foo {
> 	BAR
> };
> 
> if (sizeof(foo) != sizeof(u32))
> 	call_compat_logic().
> 
> I suspect that sizeof() won't work inside a macro. 

sizeof() is evaluated at compile time, after preprocessing. 
It should work inside of a macro.

See the ARRAY_SIZE() macro in include/linux/kernel.h for a well tested
example.

Regards,
Andy



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