On Mon, 2010-01-04 at 15:47 -0800, Greg KH wrote:
> On Mon, Jan 04, 2010 at 03:32:07PM -0800, Bruce Blinn wrote:
[...]
> > > On Sat, Jan 02, 2010 at 09:10:08PM +0800, Shawn wrote:
> > > > hello guys,
> > > > I got a newbie confused when I was looking into the source code of
> > > > s3c2440's RTC driver.I dont know what is __v excatly
> > > means.anyone can
> > > > tell?thanks anyway!
> > > >
> > > > #define readb(c) ({ __u8 __v = __raw_readb(__mem_pci(c)); __v; })
> > >
> > > __v is an variable that the macro creates and then returns
> > > the value of.
> > >
> > > Don't code like this, it's horrible :)
> >
> > Could you be more specific with what you find wrong with this. The reason I
> > ask is there is code like this all over the kernel.
>
> Like what specifically?
>
> Wrapping up a function call in a macro just because someone doesn't want
> to type the whole thing out? That's the horrible thing.
>
> Returning a temporary variable isn't a big deal, but an inline function
> is better to use as you will get the proper type safety.
So which is better (in the kernel and for this functions, macros or
whatever they really maybe!)?
a) #define readb(c) ((__u8)__raw_readb(__mem_pci(c)))
which is more a rephrase of the above
b) static inline __u8 readb(const void *c) { return __raw_readb(__mem_pci(c)); }
Caveat emptor: Not compile-tested.
Bernd
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