[PATCH 4/9] linux/const.h: Upgrade & Merge vDSO and uAPI

[Simon Glass]

Hi Pierre-Clément,

On Thu, 17 Mar 2022 at 05:00, Pierre-Clément Tosi <ptosi at google.com> wrote:
>
> On Wed, Mar 16, 2022 at 01:23:44PM -0600, Simon Glass wrote:
> > Hi Pierre-Clément,
> >
> > On Wed, 16 Mar 2022 at 09:40, Pierre-Clément Tosi <ptosi at google.com> wrote:
> > >
> > > Import the header from version 5.16 of the kernel:
> > >
> > >     commit df0cc57e057f18e44dac8e6c18aba47ab53202f9
> > >
> > > Inline <vdso/const.h> and <uapi/linux/const.h>. This is wrapped in
> > > "#ifndef __UBOOT__/#include/#else/{inline}" to better document the
> > > origin of the code being added to the U-Boot header (but not present in
> > > the original header) and make diff tools happier when comparing the file
> > > with its reference, which should be useful when porting future changes
> > > from the Linux header and/or if we decide to also import those included
> > > headers into the U-Boot codebase.
> > >
> > > Signed-off-by: Pierre-Clément Tosi <ptosi at google.com>
> > > Cc: Simon Glass <sjg at chromium.org>
> > > Cc: Tom Rini <trini at konsulko.com>
> > > ---
> > >  include/linux/const.h | 22 +++++++++++++++++++++-
> > >  1 file changed, 21 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/const.h b/include/linux/const.h
> > > index 379c889232..3e3803d767 100644
> > > --- a/include/linux/const.h
> > > +++ b/include/linux/const.h
> > > @@ -2,8 +2,13 @@
> > >  #ifndef _LINUX_CONST_H
> > >  #define _LINUX_CONST_H
> > >
> > > -/* const.h: Macros for dealing with constants.  */
> > > +#ifndef __UBOOT__
> > > +#include <vdso/const.h>
> > > +#else
> > >
> > > +#ifndef __UBOOT__
> > > +#include <uapi/linux/const.h>
> > > +#else
> > >  /* Some constant macros are used in both assembler and
> > >   * C code.  Therefore we cannot annotate them always with
> > >   * 'UL' and other type specifiers unilaterally.  We
> > > @@ -28,7 +33,22 @@
> > >  #define _BITUL(x)      (_UL(1) << (x))
> > >  #define _BITULL(x)     (_ULL(1) << (x))
> > >
> > > +#define __ALIGN_KERNEL(x, a)           __ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1)
> > > +#define __ALIGN_KERNEL_MASK(x, mask)   (((x) + (mask)) & ~(mask))
> >
> > How does this compare to the existing ALIGN()? It looks the same to me.
> >
>
> __ALIGN_KERNEL() is the uAPI counterpart to the ALIGN() kernel macro (or is it
> the other way around?) so they're intended to be similar in implementation; the
> key difference being the double-leading-underscore notation, which bears a
> special meaning as per the C Standard, and allows __ALIGN_KERNEL() to be
> considerably easier to export. In fact, the kernel currently defines
>
>     #define ALIGN(x, a)        __ALIGN_KERNEL((x), (a))
>
> For the reason why this patch introduces it here, I've taken the conservative
> approach of meticulously copying the original headers over, in their entirety
> (as far as feasible), in order to make future upgrades as smooth as possible.
>
> This patch inlines those vDSO and uAPI headers instead of bringing them as the
> stand-alone files they are in the kernel as it looks like no other kernel header
> of that kind has been imported but IMO, it would make more sense to do the
> later. What do you think?

OK I see. Using stand-alone files makes it easier to keep things in
sync in the future, but I don't have a strong opinion on it.

Reviewed-by: Simon Glass <sjg at chromium.org>

>
> > > +
> > > +#define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
> > > +#endif
> > > +
> > >  #define UL(x)          (_UL(x))
> > >  #define ULL(x)         (_ULL(x))
> > > +#endif
> > > +
> > > +/*
> > > + * This returns a constant expression while determining if an argument is
> > > + * a constant expression, most importantly without evaluating the argument.
> > > + * Glory to Martin Uecker <Martin.Uecker at med.uni-goettingen.de>
> > > + */
> > > +#define __is_constexpr(x) \
> > > +       (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
> > >
> > >  #endif /* _LINUX_CONST_H */
> > > --
> > > 2.35.1.723.g4982287a31-goog

Regards,
Simon