Pipe's related arguments to pass to a function? - c

Question

I'm a beginner in C programming and I started learning about pipes today.
I need them because my program has to run up to 4 processes at the time, so to avoid creating more processes than those required, I have to use a shared variable between all of them to keep track how may can still be created.
I tried to simplify my program:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
void forking(int p, int pid);
int main(int argc, char *argv[])
{
int fd[2];
int p = 4; // Max number of processes that can run at the same time
int pid;
if(pipe(fd) == -1)
{
perror("pipe: ");
return 0;
}
//It will try the function forking 10 times to execute SOME CODE that
// changes everytime something operates on it
for(int i = 0; i < 10; i++)
{
forking(p, pid);
}
return 0;
}
void forking(int p, int pid)
{
if (p > 0) //We can create another process
{
p -= 1; // update the p before creating a child process
write(fd[1], &p, (sizeof(int)*3)); //Tell everyone about the update
pid = fork();
if (pid == 0)
{
//The child process turn to elaborate SOME CODE
// SOME CODE
// Then there will be a point where
// we will need to check if the p has been modified!
read(fd[0], &p, sizeof(int)*3);
//So that forking can decide whether we can create another process
// to operate on SOME OTHER CODE
forking(p, pid);
//Once we are done, we can terminate the child
//but first we'll need to update the process n° p
p += 1;
write(fd[1], &p, (sizeof(int)*3));
exit(0);
}
else if(pid > 1) //Father time
{
// check the updated value
//the father will do nothing
// since a process it's already on it (on the SOME CODE part)
return;
}
}
else
{
//else the father does SOME CODE itself
// SOME CODE
}
return;
}
My 2 doubts is whether I should pass something else to the function "forking" (which can be recursive), like "fd", or if it is okay to just leave the code like this, and whether this will have the desired result.
Hopefully I made myself clear enough.
EDIT 1:
void forking(int p, int pid, int *fd)
{
if (p > 0) //We can create another process
{
p -= 1; // update the p before creating a child process
write(fd[1], &p, (sizeof(int)*3)); //Tell everyone about the update
pid = fork();
if (pid == 0)
{
//The child process turn to elaborate SOME CODE
// SOME CODE
// Then there will be a point where
// we will need to check if the p has been modified!
read(fd[0], &p, sizeof(int)*3);
//So that forking can decide whether we can create another process
// to operate on SOME OTHER CODE
forking(p, pid, fd);
//Once we are done, we can terminate the child
//but first we'll need to update the process n° p
p += 1;
write(fd[1], &p, (sizeof(int)*3));
exit(0);
}
else if(pid > 1) //Father time
{
// check the updated value
//the father will do nothing
// since a process it's already on it (on the SOME CODE part)
return;
}
}
else
{
//else the father does SOME CODE itself
// SOME CODE
}
return;
}
Passing fd resulted as a success, now I'm wondering whether I should add pipe(fd) at the start of the forking program like so . . .
void forking(int p, int pid, int *fd)
{
if(pipe(fd) == -1)
{
perror("pipe: ");
return;
}
//Rest of the code
}