From 24f0d1c533a716db29ae1d1748464a86d170da45 Mon Sep 17 00:00:00 2001
From: Stathis Kamperis <ekamperi@gmail.com>
Date: Mon, 18 Feb 2008 02:14:22 +0200
Subject: [PATCH] Add some comments

---
 cdev/mydev.c | 24 +++++++++++++-----------
 cdev/mydev.h |  2 --
 cdev/test.c  | 41 +++++++++++++++++++++++++++++++----------
 3 files changed, 44 insertions(+), 23 deletions(-)

diff --git a/cdev/mydev.c b/cdev/mydev.c
index cfcb4ca..fc7395f 100644
--- a/cdev/mydev.c
+++ b/cdev/mydev.c
@@ -16,7 +16,7 @@ struct mydev_softc {
 void mydevattach(struct device *parent, struct device *self, void *aux);
 int mydevopen(dev_t dev, int flags, int fmt, struct lwp *process);
 int mydevclose(dev_t dev, int flags, int fmt, struct lwp *process);
-int mydevioctl(dev_t dev, u_long cmd, void *data,
+int mydevioctl(dev_t dev, u_long cmd, caddr_t data,
 		      int flags, struct lwp *process);
 
 /* Just define the character dev handlers because that is all we need */
@@ -69,11 +69,11 @@ mydevclose(dev_t dev, int flags, int fmt, struct lwp *process)
  * Handle the ioctl for the dev.
  */
 int
-mydevioctl(dev_t dev, u_long cmd, void *data, int flags,
+mydevioctl(dev_t dev, u_long cmd, caddr_t data, int flags,
            struct lwp *process)
 {
-    prop_dictionary_t dict, odict;
-    prop_object_t po;
+    prop_dictionary_t dict;
+    prop_string_t ps;
     struct mydev_params *params = (struct mydev_params *)data;
     const struct plistref *pref;
     int error;
@@ -92,15 +92,17 @@ mydevioctl(dev_t dev, u_long cmd, void *data, int flags,
         error = prop_dictionary_copyin_ioctl(pref, cmd, &dict);
         if (error)
             return error;
-        odict = mydevprops;
-        mydevprops = dict;
-        prop_object_release(odict);
 
-        po = prop_dictionary_get(mydevprops, "key");
-
-        val = prop_string_cstring(po);
-        printf("<key, val> = (%s, %s)\n", "key", val);
+        ps = prop_dictionary_get(dict, "key");
+        if (ps == NULL) {
+            printf("prop_dictionary_get()\n");
+            return -1;
+        }
 
+        val = prop_string_cstring(ps);
+        prop_object_release(ps);
+        printf("<key, val> = (%s, %s)\n", "key", val == NULL ? "null" : val);
+        prop_object_release(dict);
         break;
 
     default:
diff --git a/cdev/mydev.h b/cdev/mydev.h
index dec9a95..ea0dcbd 100644
--- a/cdev/mydev.h
+++ b/cdev/mydev.h
@@ -15,8 +15,6 @@ struct mydev_params
     char string[80];
 };
 
-prop_dictionary_t mydevprops;
-
 #define MYDEVTEST _IOW('S', 0x1, struct mydev_params)
 #define MYDEVSETPROPS _IOW('S', 0x2, struct mydev_params)
 
diff --git a/cdev/test.c b/cdev/test.c
index e28ac3a..0a42cea 100644
--- a/cdev/test.c
+++ b/cdev/test.c
@@ -11,31 +11,52 @@ int main()
     struct mydev_params params;
     prop_dictionary_t pd;
     prop_string_t ps;
-    int mydev_dev;
+    int devfd;
 
     params.number = 42;
     strcpy(params.string, "Hello World");
 
-    if ((mydev_dev = open("/dev/mydev", O_RDONLY, 0)) < 0) {
+    /* Open device */
+    if ((devfd = open("/dev/mydev", O_RDONLY, 0)) < 0) {
         fprintf(stderr, "Failed to open /dev/mydev\n");
-        exit(2);
+        exit(EXIT_FAILURE);
     }
 
-    if (ioctl(mydev_dev, MYDEVTEST, &params) < 0) {
-        perror("ioctl failed");
-        exit(2);
+    /* Send ioctl request in the traditional way */
+    if (ioctl(devfd, MYDEVTEST, &params) < 0) {
+        close(devfd);
+        err("ioctl()");
     }
 
+    /* Create dictionary and add a <key, value> pair in it */
     pd = prop_dictionary_create();
+    if (pd == NULL) {
+        close(devfd);
+        err("prop_dictionary_create()");
+    }
 
     ps = prop_string_create_cstring("key");
-    prop_dictionary_set(pd, "value", ps);
+    if (ps == NULL) {
+        close(devfd);
+        prop_object_release(pd);
+        err("prop_string_create_cstring()");
+    }
+
+    if (prop_dictionary_set(pd, "value", ps) == false) {
+        close(devfd);
+        prop_object_release(ps);
+        prop_object_release(pd);
+        err("prop_dictionary_set()");
+    }
+
     prop_object_release(ps);
 
-    prop_dictionary_send_ioctl(pd, mydev_dev, MYDEVSETPROPS);
+    /* Send dictionary to kernel space */
+    prop_dictionary_send_ioctl(pd, devfd, MYDEVSETPROPS);
 
     prop_object_release(pd);
-    close(mydev_dev);
+
+    close(devfd);
     
-    exit(0);
+    return EXIT_SUCCESS;
 }
-- 
2.11.4.GIT