Hi Sudheer, On Thu, Apr 28, 2011 at 3:16 AM, Sudheer Divakaran <inbox1.sudheer@xxxxxxxxx> wrote: > Hi, > I was going through the file kernel/time.c and found the definition > of 'gettimeofday' system call as follows. > > SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv, > struct timezone __user *, tz) <--- NOTE THE COMMA between variable > types and names. > > In syscalls.h I could find the needed macros for expanding the > definition to its final form i.e., > > asmlinkage long sys_gettimeofday(struct timeval __user * tv, struct > timezone __user *tz) > > > [syscalls.h macros] > > #define SYSCALL_DEFINE2(name, ...) SYSCALL_DEFINEx(2, _##name, __VA_ARGS__) > > > #define SYSCALL_DEFINEx(x, sname, ...) \ > __SYSCALL_DEFINEx(x, sname, __VA_ARGS__) > > > #define __SYSCALL_DEFINEx(x, name, ...) \ > asmlinkage long sys##name(__SC_DECL##x(__VA_ARGS__)) > > > #define __SC_DECL1(t1, a1) t1 a1 > #define __SC_DECL2(t2, a2, ...) t2 a2, __SC_DECL1(__VA_ARGS__) > > > [Question] > Note the comma between the variable types and names in the original > definition (e.g., "struct timeval __user *, tv" instead of "struct > timeval __user *tv"). > > What is is the reason behind separating variable types and variable > names using 'comma' and latter removing the comma character using > _SC_DECLx macros? Some of the other macros, like SC_CAST1 #define __SC_CAST1(t1, a1) (t1) a1 need the type to be separated from the argument. -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
