Gilles Chanteperdrix wrote: > Wolfgang Mauerer wrote: >> Gilles Chanteperdrix wrote: >> >>> the hostrt stuff did not compile on ARM, at this chance, I had a look >>> and found a few things which I did not like: >>> - the kernel-space and user-space did not use seqcount implementations >>> from the same header, and what is more, seqcount is not available on 2.4 >>> kernels. Since we provide an implementation anyway, I changed the code >>> so that only this implementation is used both in kernel-space and >>> user-space. Prefixing everything with xn to avoid namespace clashes. >> that makes sense, good point! >> >>> - the xnarch_hostrt_data also had two different definitions, one for >>> user-space, one for kernel-space, since this definition is supposed to >>> come from newer I-pipe in kernel-space, the code did not compile with >>> older I-pipe patches. I separated xnarch_hostrt_data, the structure >>> passed by the I-pipe to do_hostrt_event, from xnvdso_hostrt_data, the >>> structure, part of the vdso used for exchanges between user-space and >>> kernel-space. We can now get xnvdso_hostrt_data defined all the time. We >>> can probably even move xnvdso_hostrt_data definition to vdso.h >> I assume your main intention is to fix the Xenomai compile when the >> underlying ipipe does not support hostrt? But when the ipipe layer is >> too old for hostrt, it does not really make sense to include hostrt >> support in the vdso -- it may be cleaner to define an empty >> stub for struct xnarch_hostrt when ipipe does not provide hostrt info. > > No. The point is to avoid the comment: "hell will break loose if this > struct is not keep in sync with one defined by the I-pipe". Having two > pieces of code relying on different headers to get the same structure > defined is really shooting ourself in the foot and asking for more. The > only case where we can admit that is when one piece of code is assembly. > And even then, it is dangerous (look at the linux kernel code, the > developers devised asm-offsets.h to solve exactly this issue). > > Besides, having two structures defined for the two different layers > allows us to modify one structure without any impact on the other. > > Keeping the structure defined even if the I-pipe does not define it is > just a side effect which avoids #ifdefery. The vdso is part of a heap > mapped in user-space, so the granularity is 4 Kbi, we do not really care > about a structure we do not use. But this is debatable, I agree. It'd be nicer to eliminate it when there's no support for it, but no religious issue here. > >>> - avoided cycle_t and u32 in order to avoid user-space namespace >>> pollution and need for many typedefs with 2.4 kernels. Using unsigned >>> long long directly instead of cycle_t revealed a bug in clocktest.c. >> While typedefs are generally debatable, the intention here was to >> create as much symmetry with the Linux kernel implementation as >> possible since this code is fairly well tested. I cannot >> point to any particular problem with the non-fixed-width definitions, >> but with them, we do at least avoid the possibility of introducing >> any scaled math issues. > > unsigned long long is 64 bits > unsigned is 32 bits > unsigned long has the natural processor word size. > So, in reality, they are fixed width definitions. Portable accross all > architectures supported by Linux. No typedefs needed.
that's correct for almost all programming models (and all reasonable ones, and certainly for everything the kernel runs on AFIK), but I still don't see a benefit in removing analogies to the kernel for no particular gain. A few lines before, you argued that things should resemble the kernel approach. Best regards, Wolfgang > >>> Here is the patch. >>> >>> diff --git a/include/nucleus/Makefile.am b/include/nucleus/Makefile.am >>> index 9a72b24..5fc1c21 100644 >>> diff --git a/include/nucleus/Makefile.in b/include/nucleus/Makefile.in >>> index 5e93dc9..a6fa801 100644 >>> diff --git a/include/nucleus/hostrt.h b/include/nucleus/hostrt.h >>> index 70ffbfe..85b8e88 100644 >>> --- a/include/nucleus/hostrt.h >>> +++ b/include/nucleus/hostrt.h >>> @@ -23,32 +23,24 @@ >>> * 02111-1307, USA. >>> */ >>> >>> -#include <nucleus/types.h> >>> -#ifdef __KERNEL__ >>> -#include <asm-generic/xenomai/system.h> >>> -#else /* !__KERNEL__ */ >>> +#ifndef __KERNEL__ >>> #include <time.h> >>> #include <sys/types.h> >>> -#include <nucleus/seqlock_user.h> >>> -typedef u_int32_t u32; >>> -typedef u_int64_t cycle_t; >>> +#else /* __KERNEL__ */ >>> +#include <asm-generic/xenomai/system.h> >>> +#endif /* __KERNEL__ */ >>> +#include <nucleus/seqlock.h> >>> >>> -/* >>> - * xnarch_hostrt_data must be kept in sync with the corresponding ipipe >>> - * definitions in ipipe_tickdev.h We cannot directly include the file >>> - * here because the definitions are also required in Xenomai userland. >>> - */ >> I think this comment may have its value. > > No. For the reason explained above. > _______________________________________________ Xenomai-core mailing list Xenomaiemail@example.com https://mail.gna.org/listinfo/xenomai-core