Re: [PATCH v6] libxl: provide libxl_bitmap_{or,and}

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2015-04-15 at 14:15 +0100, Wei Liu wrote:
> On Wed, Apr 15, 2015 at 01:45:14PM +0100, Ian Campbell wrote:
> > On Wed, 2015-04-15 at 05:45 -0600, Linda Jacobson wrote:
> > > There are new functions to provide logical and and or of two bitmaps.
> > 
> > Please could you add a sentence or two on the intended use of these
> > functions, since there are no callers being added here.
> > 
> 
> Linda is our Outreachy applicant. This is a small task that Julien and I
> assigned to her.

Sure, but that doesn't remove the need for the commit log to be a
standalone justification for the patch in its own right.

> One user I can think of is in some of the vNUMA validation functions
> that operate on bitmaps. But to keep this task small and simple I didn't
> ask her to actually use the functions she introduce.
> 
> > In particular without that I can't tell if these need to be part of the
> > public API or if they are going to be used by something internal.
> > 
> 
> I think these functions should be public functions.

Sure, but the reasoning for why you^WLinda thinks that needs to be in
the commit log. In particular because there are no users being added.

I could probably guess why you think these should be public, but I
shouldn't have to guess and in any case that doesn't help in 6 months
when someone asks "why do we have these functions".

> > If the former then I think a LIBXL_HAVE_... #define is needed in libxl.h
> > (as described by the comments in there, and there are many examples).
> > 
> 
> We're a bit lax on these functions (there is no LIBXL_HAVE_BITMAP...) 

Weren't they always there and hence don't need it?

Ian.

> so
> I didn't ask her to add one. We can add LIBXL_HAVE_BITMAP_AND_OR in
> libxl.h if you think it is necessary.
> 
> Wei.
> 
> > If the latter then the prototype should differ. (I'll explain that
> > if/when this turns out to be the case).
> > 
> > > diff --git a/tools/libxl/libxl_utils.h b/tools/libxl/libxl_utils.h
> > > index acacdd9..a128a7c 100644
> > > --- a/tools/libxl/libxl_utils.h
> > > +++ b/tools/libxl/libxl_utils.h
> > > @@ -90,6 +90,13 @@ int libxl_bitmap_test(const libxl_bitmap *bitmap, int bit);
> > >  void libxl_bitmap_set(libxl_bitmap *bitmap, int bit);
> > >  void libxl_bitmap_reset(libxl_bitmap *bitmap, int bit);
> > >  int libxl_bitmap_count_set(const libxl_bitmap *cpumap);
> > > +/* Or and and functions for two bitmaps */
> > 
> > This comment doesn't say anything which isn't already apparent from the
> > names and prototypes of the functions in question. Just leave it out.
> > 
> > 
> > > +int libxl_bitmap_or(libxl_ctx *ctx, libxl_bitmap *or_map,
> > > +                    const libxl_bitmap *map1, 
> > > +                    const libxl_bitmap *map2); 
> > > +int libxl_bitmap_and(libxl_ctx *ctx, libxl_bitmap *and_map,
> > > +                     const libxl_bitmap *map1, 
> > > +                     const libxl_bitmap *map2);
> > >  char *libxl_bitmap_to_hex_string(libxl_ctx *ctx, const libxl_bitmap *cpumap);
> > >  static inline void libxl_bitmap_set_any(libxl_bitmap *bitmap)
> > >  {
> >