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+################################################
+
+Using GCC's code coverage tool, gcov, with udev
+
+Leann Ogasawara <ogasawara@osdl.org>, April 2004
+
+################################################
+
+For more information on using gcov please see:
+
+http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
+
+With that said, here is how to get code coverage analysis for udev files.
+Note that this was developed with udev version 024.
+
+- Make sure you've installed udev and that it is working properly.
+  If you are having problems, refer to the README and HOWTO-udev_for_dev
+  documents in udev tarball.
+
+- execute make_gcov.sh from udev top level directory
+
+    make gcov-all
+
+  This will compile udev with gcov support.  Basically make_gcov.sh will
+  run make but override the CFLAGS.  It strips any optimization from
+  CFLAGS in order for gcov to get correct code coverage analysis.  It will
+  also add the -fprofile-arcs and -ftest-coverage options which are the
+  necessary flags needed to use gcov.
+
+  If you look into your udev directory and see that it has been polluted with
+  a bunch of *.gcno, *.gcda and *.gcov files. gcov creates and uses these files
+  to extract the code coverage info.
+
+- After running make_gcov.sh you need to install udev again.  So basically,
+
+    su to root
+    make install
+
+- Then execute some udev tasks.  You can run some udev tests, reboot, or
+  do anything your little udev heart desires.  Once you are satisfied, you
+  can now see how much udev code was covered.  I personally recommend just
+  running test/udev-test.pl for starters.
+
+- To get the udev code coverage analysis, execute run_gcov.sh from udev top
+  level directory.  You need to be root to do this.
+
+    su to root
+    make udev_gcov.txt
+
+- This creates udev_gcov.txt in the udev top level directory which holds all
+  the code coverage information. To see an example of the code coverage info
+  after executing the udev-test.pl test, please see:
+
+  http://developer.osdl.org/ogasawara/gcov_for_udev/udev_gcov.txt
+
+- Also, after having executed gcov on udev (ie executing run_gcov.sh) a
+  *.gcov file is created for every file which contained code that was
+  used.  Looking at the *.gcov files, one will see what lines of code
+  were hit, and what lines were missed.  For, example if code in udev-add.c
+  were executed, gcov then created a file called udev-add.c.gcov.  And a
+  portion of udev-add.c.gov might look like:
+
+  static int get_major_minor(struct sysfs_class_device *class_dev, struct udevice *udev)
+          95    {
+          95    	struct sysfs_attribute *attr = NULL;
+		
+          95    	attr = sysfs_get_classdev_attr(class_dev, "dev");
+          95    	if (attr == NULL)
+      ######    		goto error;
+			dbg("dev='%s'", attr->value);
+		
+          95    	if (sscanf(attr->value, "%u:%u", &udev->major, &udev->minor) != 2)
+      ######    		goto error;
+			dbg("found major=%d, minor=%d", udev->major, udev->minor);
+		
+          95    	return 0;
+		error:
+      ######    	return -1;
+		}
+
+  Any line of code that is preceded by a "######" implies that the code
+  was never hit during execution.
+
+- Once you are done with using gcov for udev and want to return to your
+  normal use of udev, run a regular 'make clean' on your udev directory.
+  Then just run a regular make and make install and you are back to normal:
+
+    make clean all
+    su to root
+    make install