* Ross Zwisler <ross.zwis...@linux.intel.com> wrote:
> > > > + * void flush_and_commit_buffer(void *vaddr, unsigned int size)
> > > > + * {
> > > > + * unsigned long clflush_mask = boot_cpu_data.x86_clflush_size
> > > > - 1;
> > > > + * char *vend = (char *)vaddr + size;
> >
> > So here we cast vaddr to (char *) - which is unnecessary, as 'void *'
> > has byte granular pointer arithmetics.
> >
> > And 'vend' should be void *' to begin with, to match the type
> > of 'vaddr'.
>
> The original version, copied in part from clflush_cache_range, did do
> everything with void* pointers. I changed it to use char* pointers based on
> feedback from hpa. :)
:-/
Not sure what hpa's problem with 'void *' was: especially in MM code
we are using 'void *' rather widely.
All compilers that aim for being able to build the Linux kernel
implement 'void *' as well, so that 'standard C' argument is pretty
weak IMHO - unlike some of the more esoteric GCC extensions, this one
is actually pretty well done and widely used in and outside of the
kernel.
> It seems like both have arguments for them. Char pointer arithmetic
> has the advantage that its behavior is standard in C, so it's not
> specific to gcc. I agree that void* has the advantage that it fits
> more naturally with the types of the parameters passed in, requiring
> no casting.
It's also a bonus property of 'void *' that unlike 'char *' it cannot
be dereferenced. So we use it for opaque buffers wherever we can.
> > > > + * for (p = (char *)((unsigned long)vaddr & ~clflush_mask);
> > > > + * p < vend; p += boot_cpu_data.x86_clflush_size)
> > > > + * clwb(p);
> > > > + *
> > > > + * // sfence to order clwb/clflushopt/clflush cache flushes
> > > > + * // mfence via mb() also works
> >
> > Yeah so this isn't a C++ kernel, thank all the 3000+ gods and other
> > supreme beings worshipped on this planet!
>
> Yep. C++ style // comments are happily accepted by gcc in C code, though, and
GCC accepts other C++ braindamage as well, it doesn't mean we should
use them. But:
> this was my attempt to get around the fact that /* */ style comments can't be
> nested. I couldn't think of a more elegant way of having code + comments in a
> kerneldoc comment. I agree that if this code were ever to be pulled out and
> used, the comment style would need to be corrected to be the standard kernel
> style.
I see, I didn't realize the recursion complication with DocBook - so
this bit is fine.
Thanks,
Ingo
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