Hi Andreas, On Thu, Sep 9, 2010 at 1:28 AM, Andreas Leppert <wudmx@xxxxxx> wrote: > Hi Dave, > > On Wed, Sep 08, 2010 at 11:14:30PM -0700, Dave Hylands wrote: >> Replying to the list this time... > > finally an answer to *my* problem, thanks :-D > >> Another general rule, is that on 32-bit CPUs you can only do 32-bit >> arithmetic, with 64-bit addition, subtraction, and multiplications. >> 64-bit divides must be done using do_div or do_div64. >> > > I've understood so far your explanations. But one thing I am missing: I > claim that I do not do an 64-bit division, but an 32-bit division. > > Why? I have run make tags to create an architecture dependent tags file. > When I go to s64 and jump to the definition I land in > include/asm-generic/int-l64.h . There is the typedef: > > typedef signed long s64; I think you're looking in the wrong file. include/linux/types.h includes asm/types.h arch/x86/include/asm/types.h includes asm-generic/types.h include/asm-generic/types.h includes asm-generic/int-ll64.h include/asm-generic/int-ll64.h has the following typedef for s64: typedef signed long long s64; which is in fact a 64-bit type. > On my system, the size of long int is the same as int (I've wrote a > simple C program to get this information). I.e. there should be no > difference between an 'signed int division' and an 'signed long > division'. What am I missing? > > Another question: I've encountered several #ifdef __ASSEMBLY__ and > __KERNEL__ in the header files. What do these two preprocessor > definitions stand for? I normally use __KERNEL__ in my header/source files to tell if the code is being compiled as part of the kernel, versus say being compiled as part of a boot-loader or part of a user-mode application. __ASSEMBLY__ is defined when assembling source files that include .h files. Since the preprocessor is used on .S files, the #defines are good, but the assembler doesn't understand typedefs structs, function prototypes, etc. -- Dave Hylands Shuswap, BC, Canada http://www.DaveHylands.com/ -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
