dm: mevent: implement enable/disable functions

Current mevent mevent_del/add() implementations are incomplete and buggy.
It's easier to implement  mevent_enable/disable() required for mei
virtualization. Other user of these functions, which were previously
empty stubs is the uart mediator, so far it looks working well.

Add few style issues fix on the way.

Tracked-On: #1416
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>

Author: Tomas Winkler

devicemodel/core/mevent.c

@@ -30,7 +30,6 @@
  * Micro event library for FreeBSD, designed for a single i/o thread
  * using EPOLL, and having events be persistent by default.
  */
-
 #include <assert.h>
 #include <errno.h>
 #include <stdlib.h>
@@ -59,8 +58,8 @@ static pthread_mutex_t mevent_lmutex = PTHREAD_MUTEX_INITIALIZER;
 struct mevent {
 	void	(*me_func)(int, enum ev_type, void *);
 	int	me_fd;
-	enum ev_type me_type;
-	void *me_param;
+	enum	ev_type me_type;
+	void	*me_param;
 	int	me_cq;
 	int	me_state;
 	int	me_closefd;
@@ -125,11 +124,12 @@ mevent_kq_filter(struct mevent *mevp)
 
 	if (mevp->me_type == EVF_WRITE)
 		retval = EPOLLOUT;
+
 	return retval;
 }
 
 static void
-mevent_destroy()
+mevent_destroy(void)
 {
 	struct mevent *mevp, *tmpp;
 	struct epoll_event ee;
@@ -142,9 +142,8 @@ mevent_destroy()
 		ee.data.ptr = mevp;
 		epoll_ctl(epoll_fd, EPOLL_CTL_DEL, mevp->me_fd, &ee);
 
-		if ((mevp->me_type == EVF_READ ||
-			mevp->me_type == EVF_WRITE)
-			&& mevp->me_fd != STDIN_FILENO)
+		if ((mevp->me_type == EVF_READ || mevp->me_type == EVF_WRITE) &&
+		    mevp->me_fd != STDIN_FILENO)
 			close(mevp->me_fd);
 
 		free(mevp);
@@ -221,13 +220,42 @@ mevent_add(int tfd, enum ev_type type,
 int
 mevent_enable(struct mevent *evp)
 {
-	return 0;
+	int ret;
+	struct epoll_event ee;
+	struct mevent *lp, *mevp = NULL;
+
+	mevent_qlock();
+	/* Verify that the fd/type tuple is not present in the list */
+	LIST_FOREACH(lp, &global_head, me_list) {
+		if (lp == evp) {
+			mevp = lp;
+			break;
+		}
+	}
+	mevent_qunlock();
+
+	if (!mevp)
+		return -1;
+
+	ee.events = mevent_kq_filter(mevp);
+	ee.data.ptr = mevp;
+	ret = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, mevp->me_fd, &ee);
+	if (ret < 0 && errno == EEXIST)
+		ret = 0;
+
+	return ret;
 }
 
 int
 mevent_disable(struct mevent *evp)
 {
-	return 0;
+	int ret;
+
+	ret = epoll_ctl(epoll_fd, EPOLL_CTL_DEL, evp->me_fd, NULL);
+	if (ret < 0 && errno == ENOENT)
+		ret = 0;
+
+	return ret;
 }
 
 static int
@@ -333,8 +361,8 @@ mevent_dispatch(void)
 		suspend_mode = vm_get_suspend_mode();
 
 		if ((suspend_mode != VM_SUSPEND_NONE) &&
-			(suspend_mode != VM_SUSPEND_SYSTEM_RESET) &&
-			(suspend_mode != VM_SUSPEND_SUSPEND))
+		    (suspend_mode != VM_SUSPEND_SYSTEM_RESET) &&
+		    (suspend_mode != VM_SUSPEND_SUSPEND))
 			break;
 	}
 }