[libcamera-devel] [PATCH v3 1/8] libcamera: utils: Define BIT() macro

[Jacopo Mondi]

Hi Laurent,

On Fri, Apr 05, 2019 at 02:31:13PM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Wed, Apr 03, 2019 at 05:07:28PM +0200, Jacopo Mondi wrote:
> > Define BIT(b_) macro which expands to a left bit shift.
> >
> > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > ---
> >  src/libcamera/include/utils.h | 1 +
> >  src/libcamera/utils.cpp       | 5 +++++
> >  2 files changed, 6 insertions(+)
> >
> > diff --git a/src/libcamera/include/utils.h b/src/libcamera/include/utils.h
> > index 79038a96feab..1a6cf7f7b9dc 100644
> > --- a/src/libcamera/include/utils.h
> > +++ b/src/libcamera/include/utils.h
> > @@ -10,6 +10,7 @@
> >  #include <memory>
> >
> >  #define ARRAY_SIZE(a)	(sizeof(a) / sizeof(a[0]))
> > +#define BIT(b_)		(1 << (b_))
>
> I'm curious, why the _ ? I'm also curious, why do you think we need this

To avoid (unlikely) name clashes with other 'b' variables?

> macro ? :-) Usage of BIT() in the Linux kernel is partly to fix problems
> with (1 << 31) on 32-bit platforms, with BIT() defined as (1UL << (nr)).

I just wanted something to avoid typing (1 << x) all the times, and
we're all used to the BIT() macro, so...

I could drop this if it feels not necessary...

Thanks
   j

>
> >
> >  namespace libcamera {
> >
> > diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> > index cd0fd7614cc7..1a5a2a03b1ca 100644
> > --- a/src/libcamera/utils.cpp
> > +++ b/src/libcamera/utils.cpp
> > @@ -24,6 +24,11 @@ namespace utils {
> >   * \brief Determine the number of elements in the static array.
> >   */
> >
> > +/**
> > + * \def BIT(b)
> > + * \brief Bitwise left shift by \a b bits
>
> Bitwise left shift of what ? :-)
>
> > + */
> > +
> >  /**
> >   * \brief Strip the directory prefix from the path
> >   * \param[in] path The path to process
>
> --
> Regards,
>
> Laurent Pinchart
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