[Bug 1001275] Cortex-M (armV7) architecture endian instructions / Applied on lwIP
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Mon Aug 15 20:17:00 GMT 2011
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--- Comment #2 from Sergei Gavrikov <sergei.gavrikov@gmail.com> 2011-08-15 21:17:36 BST ---
Hi Ijlija,
Thank you for your attention to low-memory footprint eCos targets and your
ideas around, i.e. how to utilize every bit on such CPUs :-)
My $.02.
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.
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_) \
);
// ---------------------------------------------------- ...
// End of cortexm_regs.h
#endif // ifdef CYGONCE_HAL_CORTEXM_REGS_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_ )
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.
Sergei
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