Hi, I want to write a Linux driver that will be generic for ARM and Intel. It will use some structures. The driver will exchange struct with hardware, so data must always have the same alignment. On ARM920, I think that we can't have a pointer on an address that is not multiple of 4. So what is the good pratice ? Only use int in structure ? To use pragma pack ? To use bit field ? Does it make a slower code ? Do you have some pointers on that subject ? In Linux source code, there are a lot of different use of pragma for aix, macintosh...: #pragma pack(1) #pragma pack() or #ifdef macintosh #pragma options align=power #endif or #ifdef macintosh #pragma options align=reset #endif or the most complicated : #ifndef NO_PACK #if defined (_DPT_AIX) #pragma options align=packed #else #pragma pack(1) #endif /* aix */ #endif // no unpack ... #ifndef NO_UNPACK #if defined (_DPT_AIX) #pragma options align=reset #elif defined (UNPACK_FOUR) #pragma pack(4) #else #pragma pack() #endif /* aix */ #endif // no unpack Why not to define something like a global macro called PRAGMA or ... instead of all this kind of hack ? Thanks for your response. -- Stephane List http://slist.lilotux.net -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
