Re: [PATCH] Corrections to Documentation/rbtree.txt

[Ian Abbott]

On 25/03/08 18:24, Rob Landley wrote:
> On Tuesday 25 March 2008 06:02:22 Ian Abbott wrote:
> > On 20/03/08 18:39, Rob Landley wrote:
> > > On Thursday 20 March 2008 10:29:57 Ian Abbott wrote:
> > > > From: Ian Abbott <abbotti@xxxxxxxxx>
> > > >
> > > > The description of the rb_entry() macro in Documentation/rbtree.txt
> > > > seems incorrect. This patch improves it (hopefully).  Also I changed the
> > > > example code to call the previous 'my_search()' example instead of an
> > > > undefined 'mysearch()'.
> > > I have no objection to the patch (and the my_search thing seems like an
> > > obvious typo), but is there a reason to prefer rb_entry() rather than
> > > container_of()?  If so, the rationale might be a good thing to add to the
> > > documentation...
> > I don't know the rationale, but all the code I can see uses rb_entry()
> > and not container_of().
>
> Except container_of() works, which is a nice thing to know, and it already 
> mentions rb_entry() as another way to do it.  If someone could explain _why_ 
> to use one over the other, that would be a good thing to add.

Let's see if Andrea Arcangeli can still remember the rationale from 9 
years ago! :-)

container_of() works just as well, but _none_ of the existing code in 
the kernel uses it to access the container of the struct rb_node; they 
all use rb_entry(), including the example code in include/linux/rbtree.h.

> Again, I don't care much either way, I just want to know what the point is of 
> choosing one over the other that makes changing what's there worth bothering 
> with.  You're changing the documentation to hide the fact that rb_entry() is 
> basically another name for container_of(), and this is supposed to be an 
> improvement?

Personally I have no preference for rb_entry() over container_of(), but 
as all the code in the kernel uses rb_entry() it seems better if the 
examples in the documentation use it too.

--
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@xxxxxxxxx>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/