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Date:   Tue, 6 Aug 2019 23:38:56 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Thomas =?iso-8859-1?Q?Hellstr=F6m_=28VMware=29?= 
        <thomas@shipmail.org>, Dave Airlie <airlied@gmail.com>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        LKML <linux-kernel@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Jerome Glisse <jglisse@redhat.com>,
        Jason Gunthorpe <jgg@mellanox.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Steven Price <steven.price@arm.com>,
        Linux-MM <linux-mm@kvack.org>
Subject: Re: drm pull for v5.3-rc1
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On Tue, Aug 06, 2019 at 11:50:42AM -0700, Linus Torvalds wrote:
> 
> In fact, I do note that a lot of the users don't actually use the
> "void *private" argument at all - they just want the walker - and just
> pass in a NULL private pointer. So we have things like this:
> 
> > +       if (walk_page_range(&init_mm, va, va + size, &set_nocache_walk_ops,
> > +                       NULL)) {
> 
> and in a perfect world we'd have arguments with default values so that
> we could skip those entirely for when people just don't need it.
> 
> I'm not a huge fan of C++ because of a lot of the complexity (and some
> really bad decisions), but many of the _syntactic_ things in C++ would
> be nice to use. This one doesn't seem to be one that the gcc people
> have picked up as an extension ;(
> 
> Yes, yes, we could do it with a macro, I guess.
> 
>    #define walk_page_range(mm, start,end, ops, ...) \
>        __walk_page_range(mm, start, end, (NULL , ## __VA_ARGS__))
> 
> but I'm not sure it's worthwhile.

Given that is is just a single argument I'm not to worried.  A simpler
and a more complex variant seems more useful if we can skip a few
arguments IMHO.