Re: [PATCH 6/8] qemu/bswap: Add const_le64()

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Wed, 11 Jan 2023 17:40:46 +0100
Philippe Mathieu-Daudé <philmd@linaro.org> wrote:

> On 11/1/23 15:24, Jonathan Cameron via wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> > 
> > Gcc requires constant versions of cpu_to_le* calls.
> > 
> > Add a 64 bit version.
> > 
> > Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > ---
> >   include/qemu/bswap.h | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> > 
> > diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
> > index 346d05f2aa..e1eca22f25 100644
> > --- a/include/qemu/bswap.h
> > +++ b/include/qemu/bswap.h
> > @@ -187,6 +187,15 @@ CPU_CONVERT(le, 64, uint64_t)
> >    * used to initialize static variables.
> >    */
> >   #if HOST_BIG_ENDIAN
> > +# define const_le64(_x)                          \
> > +    ((((_x) & 0x00000000000000ffU) << 56) |      \
> > +     (((_x) & 0x000000000000ff00U) << 40) |      \
> > +     (((_x) & 0x0000000000ff0000U) << 24) |      \
> > +     (((_x) & 0x00000000ff000000U) <<  8) |      \
> > +     (((_x) & 0x000000ff00000000U) >>  8) |      \
> > +     (((_x) & 0x0000ff0000000000U) >> 24) |      \
> > +     (((_x) & 0x00ff000000000000U) >> 40) |      \
> > +     (((_x) & 0xff00000000000000U) >> 56))  
> 
> So looking back at 
> https://lore.kernel.org/qemu-devel/20200917163106.49351-4-philmd@redhat.com/
> this patch missed to update the function description:
> 
>   /*
> - * Same as cpu_to_{be,le}{16,32} described below, except that gcc will
> + * Same as cpu_to_{be,le}{16,32,64} described below, except that gcc will
>    * figure the result is a compile-time constant if you pass in a constant.
>    * So this can be used to initialize static variables.
>    */

Good point.  The context is a little difference as your series had combined
several comments into one, but I've put in a similar update.

Obviously if your series lands first we can drop this one, but I'll carry
it forwards for now.

Thanks,

Jonathan

> 
>