Add Task 12 description

Task12/task12.txt

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+This is Task 12 of the Eudyptula Challenge
+------------------------------------------
+
+Nice job with the driver patch.  That took some work in finding the
+proper place to modify, and demonstrates a great skill in tracking down
+issues when you can't get a specific piece of hardware working.
+
+Now let's step back from drivers (they are boring things), and focus on
+the kernel core.  To do that, we need to go way back to the basics --
+stuff you would learn in your "intro to data structures" class, if you
+happened to take one.
+
+Yes, I'm talking about linked lists.
+
+The kernel has a unique way of creating and handling linked lists, that
+is quite different than the "textbook" way of doing so.  But, it turns
+out to be faster, and simpler, than a "textbook" would describe, so
+that's a good thing.
+
+For this task, write a kernel module, based on your cleaned up one from
+task 04, that does the following:
+  - You have a structure that has 3 fields:
+        char  name[20];
+        int   id;
+        bool  busy;
+    name this structure "identity".
+  - Your module has a static variable that points to a list of these
+    "identity" structures.
+  - Write a function that looks like:
+        int identity_create(char *name, int id)
+    that creates the structure "identity", copies in the 'name' and 'id'
+    fields and sets 'busy' to false.  Proper error checking for out of
+    memory issues is required.  Return 0 if everything went ok; an error
+    value if something went wrong.
+  - Write a function that looks like:
+        struct identity *identity_find(int id);
+    that takes a given id, iterates over the list of all ids, and
+    returns the proper 'struct identity' associated with it.  If the
+    identity is not found, return NULL.
+  - Write a function that looks like:
+        void identity_destroy(int id);
+    that given an id, finds the proper 'struct identity' and removes it
+    from the system.
+  - Your module_init() function will look much like the following:
+
+        struct identity *temp;
+
+        identity_create("Alice", 1);
+        identity_create("Bob", 2);
+        identity_create("Dave", 3);
+        identity_create("Gena", 10);
+
+        temp = identity_find(3);
+        pr_debug("id 3 = %s\n", temp->name);
+
+        temp = identity_find(42);
+        if (temp == NULL)
+                pr_debug("id 42 not found\n");
+
+        identity_destroy(2);
+        identity_destroy(1);
+        identity_destroy(10);
+        identity_destroy(42);
+        identity_destroy(3);
+
+   Bonus points for properly checking return values of the above
+   functions.
+
+As always, please send the full module (following the proper kernel
+coding style rules), and "proof" of it working properly.  And remember
+to use your id of "[redacted]" in the Subject line properly.