Re: [Xen-devel] [PATCH v5 05/14] tools/libxc: unused attribute in DECLARE_HYPERCALL_BUFFER_SHADOW

[Yang Hongyang <yanghy@xxxxxxxxxxxxxx>]

On 05/13/2015 11:57 PM, Ian Campbell wrote:
> On Wed, 2015-05-13 at 09:53 +0800, Yang Hongyang wrote:
> > There are cases that we only need to use the hypercall buffer data,
> "cases where"
> > and do not use the xc_hypercall_buffer_t struct.
> > DECLARE_HYPERCALL_BUFFER_SHADOW define a user pointer that can allow
> "defines a user pointer"
>
> > us to access the hypercall buffer data but it also define a
> "defines"
>
> > xc_hypercall_buffer_t that we don't use, the compiler will report arg
> > unused error.
> > add __attribute__((unused)) before xc_hypercall_buffer_t to avoid
> > the compiler error.
> >
> > The cases for example:
> "Example cases:"
>
> > In send_all_pages(), we only need to use the haypercall buffer data
> "hypercall"
>
> > which is a dirty bitmap, we set the dirty bitmap to all dirty and call
> > send_dirty_pages, we will not use the xc_hypercall_buffer_t and hypercall
> > to retrive the dirty bitmap.
> "retrieve"
>
> > In send_some_pages(), we will also only need to use the dirty_bitmap.
> > the retrive dirty bitmap hypercall are done by the caller.
> and again.
>
> > Signed-off-by: Yang Hongyang <yanghy@xxxxxxxxxxxxxx>
> > CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> > CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> > CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> > CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > ---
> >   tools/libxc/include/xenctrl.h | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> > index a689caf..0804257 100644
> > --- a/tools/libxc/include/xenctrl.h
> > +++ b/tools/libxc/include/xenctrl.h
> > @@ -284,11 +284,15 @@ typedef struct xc_hypercall_buffer xc_hypercall_buffer_t;
> >    * Useful when a hypercall buffer is passed to a function and access
> >    * via the user pointer is required.
> >    *
> > + * The shadow xc_hypercall_buffer_t may be unused, add
> > + * __attribute__((unused)) to avoid compiler error.
> No need for this comment IMHO.
>
> >    * See DECLARE_HYPERCALL_BUFFER_ARGUMENT() if the user pointer is not
> >    * required.
> >    */
> >   #define DECLARE_HYPERCALL_BUFFER_SHADOW(_type, _name, _hbuf)   \
> >       _type *(_name) = (_hbuf)->hbuf;                            \
> > +    __attribute__((unused))                                    \
> This is a somewhat unconventional location for such a tagm but putting
> it elsewhere would involve faff-some rewrapping.
>
> So apart from the typos looks good.
Will fix those typos, thank you!

> >       xc_hypercall_buffer_t XC__HYPERCALL_BUFFER_NAME(_name) = { \
> >           .hbuf = (void *)-1,                                    \
> >           .param_shadow = (_hbuf),                               \
>
> .
--
Thanks,
Yang.

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