From 482580565ffe4b161c2aa64d86c62ffe5a0857a9 Mon Sep 17 00:00:00 2001
From: Matthias Kruk <m@m10k.eu>
Date: Mon, 28 Oct 2019 18:35:32 +0900
Subject: [PATCH] Add an argument to process_create() so the caller may request
 the process to be created with a specific pid

---
 kernel/core/process.c    | 28 ++++++++++++++++++++++++++--
 kernel/include/process.h |  2 +-
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/kernel/core/process.c b/kernel/core/process.c
index 7b9b8ae..e4fb472 100644
--- a/kernel/core/process.c
+++ b/kernel/core/process.c
@@ -75,12 +75,30 @@ static inline int DQ(process_t *p)
 	return(ret_val);
 }
 
-int process_create(process_t **dst, u32_t ppl, void *entry)
+int process_create(process_t **dst, pid_t pid, u32_t ppl, void *entry)
 {
 	int ret_val;
 	process_t *proc;
 
 	ret_val = -ENOMEM;
+	proc = NULL;
+
+	/* was a specific pid requested? */
+	if(pid != PID_ANY) {
+		/* may only request pids in [2..100] */
+
+		if(pid < 2 || pid >= 100) {
+			ret_val = -EINVAL;
+			goto cleanup;
+		}
+
+		/* check if pid is already taken */
+		if(process_lookup(pid)) {
+			ret_val = -EALREADY;
+			goto cleanup;
+		}
+	}
+
 	proc = kmalloc(sizeof(*proc));
 
 	if(proc) {
@@ -106,7 +124,13 @@ int process_create(process_t **dst, u32_t ppl, void *entry)
 		}
 
 		proc->p_privl = ppl;
-		proc->p_id = _next_pid++;
+
+		if(pid == PID_ANY) {
+			/* no specific pid requested */
+			proc->p_id = _next_pid++;
+		} else {
+			proc->p_id = pid;
+		}
 
 		task_prepare(proc->p_tasks, (u32_t)pdbr, (u32_t)entry,
 					 (u32_t)kstack + CONFIG_KERNEL_STACK_SIZE,
diff --git a/kernel/include/process.h b/kernel/include/process.h
index 6ec4286..ca42c6e 100644
--- a/kernel/include/process.h
+++ b/kernel/include/process.h
@@ -24,7 +24,7 @@
 
 typedef struct process process_t;
 
-int process_create(process_t**, u32_t, void*);
+int process_create(process_t**, pid_t, u32_t, void*);
 int process_switch(process_t*);
 
 int process_falloc(process_t*, int);
-- 
2.47.3