This is the mail archive of the
ecos-patches@sourceware.org
mailing list for the eCos project.
[Bug 1001275] Cortex-M (armV7) architecture endian instructions / Applied on lwIP
- From: bugzilla-daemon at bugs dot ecos dot sourceware dot org
- To: ecos-patches at ecos dot sourceware dot org
- Date: Thu, 18 Aug 2011 22:14:25 +0100
- Subject: [Bug 1001275] Cortex-M (armV7) architecture endian instructions / Applied on lwIP
- Auto-submitted: auto-generated
- References: <bug-1001275-104@http.bugs.ecos.sourceware.org/>
Please do not reply to this email. Use the web interface provided at:
http://bugs.ecos.sourceware.org/show_bug.cgi?id=1001275
--- Comment #4 from Sergei Gavrikov <sergei.gavrikov@gmail.com> 2011-08-18 22:14:20 BST ---
(In reply to comment #3 from IK)
> (In reply to comment #2 from SG)
> > Instead hal_arch_instr.h I would create <arch>_regs.h header file to
> > define a few instructions in assembler. In your case it is
> > cortexm_regs.h.
> >
> > NOTE: There are the precendents of such definitions in other
> > architecture trees.
> >
>
> Right! Actually I was looking for such a header but obviously not hard
> enough. I would have been happier if file name was hal_regs.h, but
> let's not break the habit, and use cortexm_regs.h
>
> > I mean (snippets not tested!)
> >
> > #ifndef CYGONCE_HAL_CORTEXM_REGS_H
> > #define CYGONCE_HAL_CORTEXM_REGS_H
> > //==================================================== ...
> > //
> > // cortexm_regs.h
> > //
> > // Cortex-M CPU definitions
> > //
> > // ...
> >
> > #include <pkgconf/hal.h>
> >
> > #include <cyg/hal/var_regs.h>
> >
> > // Macro to embed rev instructions in C code
> > #define CYGARC_REV(_origin_, _swapped_) \
> > asm volatile( "rev %0, %1\n" \
> > : "=r" (_swapped_) \
> > : "r" (_origin_) \
> > );
> >
> > #define CYGARC_REV16(_origin_, _swapped_) \
> > asm volatile( "rev16 %0, %1\n" \
> > : "=r" (_swapped_) \
> > : "r" (_origin_) \
> > );
>
>
> // We could also define the functions, now using macros.
Then my question, Where did you plan to define and implement them?
> // In context with this please look at discussion
> // regarding lwIP below.
> // Regarding functions I have one dillema:
> // Could we rename cygarc_arm_rev*() functions into cygarc_byteswap*()?
IMHO, as hal_endian.h contains
#ifndef CYG_SWAP16
# define CYG_SWAP16(_x_)
...
#ifndef CYG_SWAP32
# define CYG_SWAP32(_x_)
...
And you would just define own versions (see below).
> #define CYGARC_HAL_INSTR_ATTR \
> __externC __attribute__(( always_inline )) inline
>
> // This is an optional name for cygarc_arm_rev()
> // CYGARC_HAL_INSTR_ATTR cyg_uint32 cygarc_byteswap(cyg_uint32 original){
>
> CYGARC_HAL_INSTR_ATTR cyg_uint32 cygarc_arm_rev(cyg_uint32 original){
> cyg_uint32 swapped;
> CYGARC_REV(swapped, original);
> return swapped;
> }
[snip]
Ilija, Do you really need in C90 inline attribute? Do you really need
extern inlines. AFAIK, extern + inline is almost macro and what is about
#ifndef CYGARC_SWAP16(_x_)
#define CYGARC_SWAP16(_x_) cygarc_swap16(_x_)
static __inline__ cygarc_swap16(_original_)
{
cyg_uint16 _swapped_;
CYGARC_REV16(_orginal_, _swapped_);
return _swapped_;
}
...
etc.
> // Platform supports endian operations.
> #define CYGARC_BYTESWAP 1
OK, or may be CYGARC_SWAPXX.
> #define CYGARC_BYTESWAP32(__val) cygarc_arm_rev(__val)
> #define CYGARC_BYTESWAP16(__val) ((cyg_uint16)cygarc_arm_rev16(__val))
I would prefer those short names or may be even CYG_SWAP16, CYG_SWAP32;
also I would not put the above definitions in cortexm_regs.h. In my
opinion CYGARC_SWAP16, CYGARC_SWAP32 can be placed in hal_arch.h.
> > And then I would add only needed inline functions and declarations
> > in some header file (again, not tested)
> >
> > #include <cyg/hal/cortexm_regs.h>
> >
> > #define LWIP_PLATFORM_HTONL( _hostlong_ ) hal_htol( _hostlong_ )
> > #define LWIP_PLATFORM_HTONS( _hostshort_ ) hal_htos( _hostshort_ )
>
> I think that it wouldn't be appropriate to use ARM-related mnemonics
> (CYGARC_REV) in lwIP subtree. Also we should avoid, putting lwIP -
> related names into HAL. For this reason I have defined
> CYGARC_BUTESWAPxx() - architecture neutral macro name that could be
> used in other architectures as appropriate.
Agreed. But, I told about some invented `hal_net.h' thought. Above and
below was for such a header. See below.
> > static inline cyg_uint32 hal_htonl(cyg_uint32 hostslong)
> > {
> > cyg_uint32 netlong;
> > CYGARC_REV(hostlong, netlong);
> > return netlong;
> > }
> >
> > static inline cyg_uint16 hal_htons(cyg_uint16 hostshort)
> > {
> > cyg_uint16 netshort;
> > CYGARC_REV16(hostshort, netshort);
> > return netshort;
> > }
> >
> >
> > But, I would resist to put them in hal_arch.h ... And it is mine
> > only. By other hand lwipopts.h includes that header only. I thought
> > it's pitty that we have hal_io.h, but not hal_net.h. Thus, we need
> > more expert views on code's arrangement.
Now you see. That was just thoughts.
> I think that hal_arch.h isn't bad, after all cortexm_regs.h belong to
> hal and is architecture specific.
Ilija, IMHO
1) <hal>_regs.h is for registers, opcodes, mnemonics, and asm inlines
definitions. So, let's put a few CYGARC_REV* defines there for now.
2) We can define CYGARC_SWAPxx or CYG_SWAPxx macros and put there static
inlines for them in hal_arch.h.
I would avoid C90 inline attributes (always_inline) in hal_arch.h as
it is GCC4-ish and I would quote here "one never knows what the next
annoying compiler will demand" :-)
Look, I configured/build eCos for stm3210e (default+lwip) and I've
got
% grep hal_arch.h --include=*.d -r . | wc -l
107
The hal_arch.h is a very important header and I would not risk to add
more compiler dependences there.
If it (always_inline) uses itself only for one module it is not big
deal I even know where is such an application in eCos. That is eCos
`framebuf' package. Look, please, at framebuf.inl. But only one C
source (linear.c) uses those "always inlined" functions and by the
way they declared as static.
3) If we will define SWAP16/32 in hal_arch.h then lwiopts.h can get
almost yours (just an example)
#ifdef CYGARC_SWAPXX
# define LWIP_PLATFORM_BYTESWAP 1
# define LWIP_PLATFORM_HTONS(__val) CYGARC_SWAP16(__val)
# define LWIP_PLATFORM_HTONL(__val) CYGARC_SWAP32(__val)
#endif
Well, it is my view only. I hope that I did not miss something.
> I am not able to run the code at present but it builds without
> warnings. Disassembly looks as expected.
>
> Ilija
It's good to know. Thank you for feedback.
Sergei
--
Configure bugmail: http://bugs.ecos.sourceware.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.