diff --git a/study/debug/trace/Makefile b/study/debug/trace/Makefile
new file mode 100644
index 0000000..49ea901
--- /dev/null
+++ b/study/debug/trace/Makefile
@@ -0,0 +1,79 @@
+# ------------------------------------------------------------------------------
+#
+# Makefile for the LDD-LinuxDeviceDrivers.
+#
+# Author: gatieme
+# Create: 2016-07-29 15:50:46
+# Last modified: 2016-07-29 16:10:29
+# Description:
+# 	This program is loaded as a kernel(v2.6.18 or later) module.
+# 	Use "make install" to load it into kernel.
+# 	Use "make remove" to remove the module out of kernel.
+#
+# ------------------------------------------------------------------------------
+
+
+#	my driver description
+DRIVER_VERSION := "1.0.0"
+DRIVER_AUTHOR  := "Gatieme @ AderStep Inc..."
+DRIVER_DESC    := "Linux input module for Elo MultiTouch(MT) devices"
+DRIVER_LICENSE := "Dual BSD/GPL"
+
+
+MODULE_NAME := trace-events-sample
+MODCFLAGS:=-O6 -Wall -DMODULE -D__KERNEL__ -DLINUX -std=c99
+CFG_FLAGS += -O2  -I./
+EXTRA_CFLAGS  += $(C_FLAGS) $(CFG_INC) $(CFG_INC)
+
+
+
+ifneq ($(KERNELRELEASE),)
+
+
+
+
+obj-m := $(MODULE_NAME).o #print_vmarea.o
+
+else
+
+KERNELDIR ?= /lib/modules/$(shell uname -r)/build
+
+PWD := $(shell pwd)
+
+modules:
+	make -C $(KERNELDIR) M=$(PWD) modules
+
+modules_install:
+	make -C $(KERNELDIR) M=$(PWD) modules_install
+
+
+
+insmod:
+	sudo insmod $(MODULE_NAME).ko
+
+reinsmod:
+	sudo rmmod $(MODULE_NAME)
+	sudo insmod $(MODULE_NAME).ko
+
+github:
+	cd $(ROOT) && make github
+
+rmmod:
+	sudo rmmod $(MODULE_NAME)
+
+test :
+	cat /sys/kernel/debug/mydebug/a
+	cat /sys/kernel/debug/mydebug/b
+	cat /sys/kernel/debug/mydebug/subdir/c
+
+clean:
+	make -C $(KERNELDIR) M=$(PWD) clean
+	rm -f modules.order Module.symvers Module.markers
+
+.PHNOY:
+	modules modules_install clean
+
+
+
+endif
+
diff --git a/study/debug/trace/trace-events-sample.c b/study/debug/trace/trace-events-sample.c
new file mode 100644
index 0000000..81d2d46
--- /dev/null
+++ b/study/debug/trace/trace-events-sample.c
@@ -0,0 +1,131 @@
+#include <linux/module.h>
+#include <linux/kthread.h>
+
+/*
+ * Any file that uses trace points, must include the header.
+ * But only one file, must include the header by defining
+ * CREATE_TRACE_POINTS first.  This will make the C code that
+ * creates the handles for the trace points.
+ */
+#define CREATE_TRACE_POINTS
+#include "trace-events-sample.h"
+
+static const char *random_strings[] = {
+        "Mother Goose",
+        "Snoopy",
+        "Gandalf",
+        "Frodo",
+        "One ring to rule them all"
+};
+
+static void simple_thread_func(int cnt)
+{
+        int array[6];
+        int len = cnt % 5;
+        int i;
+
+        set_current_state(TASK_INTERRUPTIBLE);
+        schedule_timeout(HZ);
+
+        for (i = 0; i < len; i++)
+                array[i] = i + 1;
+        array[i] = 0;
+
+        /* Silly tracepoints */
+        trace_foo_bar("hello", cnt, array, random_strings[len],
+                      tsk_cpus_allowed(current));
+
+        trace_foo_with_template_simple("HELLO", cnt);
+
+        trace_foo_bar_with_cond("Some times print", cnt);
+
+        trace_foo_with_template_cond("prints other times", cnt);
+
+        trace_foo_with_template_print("I have to be different", cnt);
+}
+
+static int simple_thread(void *arg)
+{
+        int cnt = 0;
+
+        while (!kthread_should_stop())
+                simple_thread_func(cnt++);
+
+        return 0;
+}
+
+static struct task_struct *simple_tsk;
+static struct task_struct *simple_tsk_fn;
+
+static void simple_thread_func_fn(int cnt)
+{
+        set_current_state(TASK_INTERRUPTIBLE);
+        schedule_timeout(HZ);
+
+        /* More silly tracepoints */
+        trace_foo_bar_with_fn("Look at me", cnt);
+        trace_foo_with_template_fn("Look at me too", cnt);
+}
+
+static int simple_thread_fn(void *arg)
+{
+        int cnt = 0;
+
+        while (!kthread_should_stop())
+                simple_thread_func_fn(cnt++);
+
+        return 0;
+}
+
+static DEFINE_MUTEX(thread_mutex);
+
+int foo_bar_reg(void)
+{
+        pr_info("Starting thread for foo_bar_fn\n");
+        /*
+         * We shouldn't be able to start a trace when the module is
+         * unloading (there's other locks to prevent that). But
+         * for consistency sake, we still take the thread_mutex.
+         */
+        mutex_lock(&thread_mutex);
+        simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
+        mutex_unlock(&thread_mutex);
+        return 0;
+}
+
+void foo_bar_unreg(void)
+{
+        pr_info("Killing thread for foo_bar_fn\n");
+        /* protect against module unloading */
+        mutex_lock(&thread_mutex);
+        if (simple_tsk_fn)
+                kthread_stop(simple_tsk_fn);
+        simple_tsk_fn = NULL;
+        mutex_unlock(&thread_mutex);
+}
+
+static int __init trace_event_init(void)
+{
+        simple_tsk = kthread_run(simple_thread, NULL, "event-sample");
+        if (IS_ERR(simple_tsk))
+                return -1;
+
+        return 0;
+}
+
+static void __exit trace_event_exit(void)
+{
+        kthread_stop(simple_tsk);
+        mutex_lock(&thread_mutex);
+        if (simple_tsk_fn)
+                kthread_stop(simple_tsk_fn);
+        simple_tsk_fn = NULL;
+        mutex_unlock(&thread_mutex);
+}
+
+module_init(trace_event_init);
+module_exit(trace_event_exit);
+
+MODULE_AUTHOR("Steven Rostedt");
+MODULE_DESCRIPTION("trace-events-sample");
+MODULE_LICENSE("GPL");
diff --git a/study/debug/trace/trace-events-sample.h b/study/debug/trace/trace-events-sample.h
new file mode 100644
index 0000000..d1269f5
--- /dev/null
+++ b/study/debug/trace/trace-events-sample.h
@@ -0,0 +1,523 @@
+/*
+ * If TRACE_SYSTEM is defined, that will be the directory created
+ * in the ftrace directory under /sys/kernel/tracing/events/<system>
+ *
+ * The define_trace.h below will also look for a file name of
+ * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
+ * In this case, it would look for sample-trace.h
+ *
+ * If the header name will be different than the system name
+ * (as in this case), then you can override the header name that
+ * define_trace.h will look up by defining TRACE_INCLUDE_FILE
+ *
+ * This file is called trace-events-sample.h but we want the system
+ * to be called "sample-trace". Therefore we must define the name of this
+ * file:
+ *
+ * #define TRACE_INCLUDE_FILE trace-events-sample
+ *
+ * As we do an the bottom of this file.
+ *
+ * Notice that TRACE_SYSTEM should be defined outside of #if
+ * protection, just like TRACE_INCLUDE_FILE.
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM sample-trace
+
+/*
+ * TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric
+ * and underscore), although it may start with numbers. If for some
+ * reason it is not, you need to add the following lines:
+ */
+#undef TRACE_SYSTEM_VAR
+#define TRACE_SYSTEM_VAR sample_trace
+/*
+ * But the above is only needed if TRACE_SYSTEM is not alpha-numeric
+ * and underscored. By default, TRACE_SYSTEM_VAR will be equal to
+ * TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if
+ * TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with
+ * only alpha-numeric and underscores.
+ *
+ * The TRACE_SYSTEM_VAR is only used internally and not visible to
+ * user space.
+ */
+
+/*
+ * Notice that this file is not protected like a normal header.
+ * We also must allow for rereading of this file. The
+ *
+ *  || defined(TRACE_HEADER_MULTI_READ)
+ *
+ * serves this purpose.
+ */
+#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_EVENT_SAMPLE_H
+
+/*
+ * All trace headers should include tracepoint.h, until we finally
+ * make it into a standard header.
+ */
+#include <linux/tracepoint.h>
+
+/*
+ * The TRACE_EVENT macro is broken up into 5 parts.
+ *
+ * name: name of the trace point. This is also how to enable the tracepoint.
+ *   A function called trace_foo_bar() will be created.
+ *
+ * proto: the prototype of the function trace_foo_bar()
+ *   Here it is trace_foo_bar(char *foo, int bar).
+ *
+ * args:  must match the arguments in the prototype.
+ *    Here it is simply "foo, bar".
+ *
+ * struct:  This defines the way the data will be stored in the ring buffer.
+ *          The items declared here become part of a special structure
+ *          called "__entry", which can be used in the fast_assign part of the
+ *          TRACE_EVENT macro.
+ *
+ *      Here are the currently defined types you can use:
+ *
+ *   __field : Is broken up into type and name. Where type can be any
+ *         primitive type (integer, long or pointer).
+ *
+ *        __field(int, foo)
+ *
+ *        __entry->foo = 5;
+ *
+ *   __field_struct : This can be any static complex data type (struct, union
+ *         but not an array). Be careful using complex types, as each
+ *         event is limited in size, and copying large amounts of data
+ *         into the ring buffer can slow things down.
+ *
+ *         __field_struct(struct bar, foo)
+ *
+ *         __entry->bar.x = y;
+
+ *   __array: There are three fields (type, name, size). The type is the
+ *         type of elements in teh array, the name is the name of the array.
+ *         size is the number of items in the array (not the total size).
+ *
+ *         __array( char, foo, 10) is the same as saying: char foo[10];
+ *
+ *         Assigning arrays can be done like any array:
+ *
+ *         __entry->foo[0] = 'a';
+ *
+ *         memcpy(__entry->foo, bar, 10);
+ *
+ *   __dynamic_array: This is similar to array, but can vary its size from
+ *         instance to instance of the tracepoint being called.
+ *         Like __array, this too has three elements (type, name, size);
+ *         type is the type of the element, name is the name of the array.
+ *         The size is different than __array. It is not a static number,
+ *         but the algorithm to figure out the length of the array for the
+ *         specific instance of tracepoint. Again, size is the numebr of
+ *         items in the array, not the total length in bytes.
+ *
+ *         __dynamic_array( int, foo, bar) is similar to: int foo[bar];
+ *
+ *         Note, unlike arrays, you must use the __get_dynamic_array() macro
+ *         to access the array.
+ *
+ *         memcpy(__get_dynamic_array(foo), bar, 10);
+ *
+ *         Notice, that "__entry" is not needed here.
+ *
+ *   __string: This is a special kind of __dynamic_array. It expects to
+ *         have a nul terminated character array passed to it (it allows
+ *         for NULL too, which would be converted into "(null)"). __string
+ *         takes two paramenter (name, src), where name is the name of
+ *         the string saved, and src is the string to copy into the
+ *         ring buffer.
+ *
+ *         __string(foo, bar)  is similar to:  strcpy(foo, bar)
+ *
+ *         To assign a string, use the helper macro __assign_str().
+ *
+ *         __assign_str(foo, bar);
+ *
+ *         In most cases, the __assign_str() macro will take the same
+ *         parameters as the __string() macro had to declare the string.
+ *
+ *   __bitmask: This is another kind of __dynamic_array, but it expects
+ *         an array of longs, and the number of bits to parse. It takes
+ *         two parameters (name, nr_bits), where name is the name of the
+ *         bitmask to save, and the nr_bits is the number of bits to record.
+ *
+ *         __bitmask(target_cpu, nr_cpumask_bits)
+ *
+ *         To assign a bitmask, use the __assign_bitmask() helper macro.
+ *
+ *         __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits);
+ *
+ *
+ * fast_assign: This is a C like function that is used to store the items
+ *    into the ring buffer. A special variable called "__entry" will be the
+ *    structure that points into the ring buffer and has the same fields as
+ *    described by the struct part of TRACE_EVENT above.
+ *
+ * printk: This is a way to print out the data in pretty print. This is
+ *    useful if the system crashes and you are logging via a serial line,
+ *    the data can be printed to the console using this "printk" method.
+ *    This is also used to print out the data from the trace files.
+ *    Again, the __entry macro is used to access the data from the ring buffer.
+ *
+ *    Note, __dynamic_array, __string, and __bitmask require special helpers
+ *       to access the data.
+ *
+ *      For __dynamic_array(int, foo, bar) use __get_dynamic_array(foo)
+ *            Use __get_dynamic_array_len(foo) to get the length of the array
+ *            saved. Note, __get_dynamic_array_len() returns the total allocated
+ *            length of the dynamic array; __print_array() expects the second
+ *            parameter to be the number of elements. To get that, the array length
+ *            needs to be divided by the element size.
+ *
+ *      For __string(foo, bar) use __get_str(foo)
+ *
+ *      For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus)
+ *
+ *
+ * Note, that for both the assign and the printk, __entry is the handler
+ * to the data structure in the ring buffer, and is defined by the
+ * TP_STRUCT__entry.
+ */
+
+/*
+ * It is OK to have helper functions in the file, but they need to be protected
+ * from being defined more than once. Remember, this file gets included more
+ * than once.
+ */
+#ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS
+#define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS
+static inline int __length_of(const int *list)
+{
+        int i;
+
+        if (!list)
+                return 0;
+
+        for (i = 0; list[i]; i++)
+                ;
+        return i;
+}
+
+enum {
+        TRACE_SAMPLE_FOO = 2,
+        TRACE_SAMPLE_BAR = 4,
+        TRACE_SAMPLE_ZOO = 8,
+};
+#endif
+
+/*
+ * If enums are used in the TP_printk(), their names will be shown in
+ * format files and not their values. This can cause problems with user
+ * space programs that parse the format files to know how to translate
+ * the raw binary trace output into human readable text.
+ *
+ * To help out user space programs, any enum that is used in the TP_printk()
+ * should be defined by TRACE_DEFINE_ENUM() macro. All that is needed to
+ * be done is to add this macro with the enum within it in the trace
+ * header file, and it will be converted in the output.
+ */
+
+TRACE_DEFINE_ENUM(TRACE_SAMPLE_FOO);
+TRACE_DEFINE_ENUM(TRACE_SAMPLE_BAR);
+TRACE_DEFINE_ENUM(TRACE_SAMPLE_ZOO);
+
+TRACE_EVENT(foo_bar,
+
+        TP_PROTO(const char *foo, int bar, const int *lst,
+                 const char *string, const struct cpumask *mask),
+
+        TP_ARGS(foo, bar, lst, string, mask),
+
+        TP_STRUCT__entry(
+                __array(        char,   foo,    10              )
+                __field(        int,    bar                     )
+                __dynamic_array(int,    list,   __length_of(lst))
+                __string(       str,    string                  )
+                __bitmask(      cpus,   num_possible_cpus()     )
+        ),
+
+        TP_fast_assign(
+                strlcpy(__entry->foo, foo, 10);
+                __entry->bar    = bar;
+                memcpy(__get_dynamic_array(list), lst,
+                       __length_of(lst) * sizeof(int));
+                __assign_str(str, string);
+                __assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus());
+        ),
+
+        TP_printk("foo %s %d %s %s %s %s (%s)", __entry->foo, __entry->bar,
+
+/*
+ * Notice here the use of some helper functions. This includes:
+ *
+ *  __print_symbolic( variable, { value, "string" }, ... ),
+ *
+ *    The variable is tested against each value of the { } pair. If
+ *    the variable matches one of the values, then it will print the
+ *    string in that pair. If non are matched, it returns a string
+ *    version of the number (if __entry->bar == 7 then "7" is returned).
+ */
+                  __print_symbolic(__entry->bar,
+                                   { 0, "zero" },
+                                   { TRACE_SAMPLE_FOO, "TWO" },
+                                   { TRACE_SAMPLE_BAR, "FOUR" },
+                                   { TRACE_SAMPLE_ZOO, "EIGHT" },
+                                   { 10, "TEN" }
+                          ),
+
+/*
+ *  __print_flags( variable, "delim", { value, "flag" }, ... ),
+ *
+ *    This is similar to __print_symbolic, except that it tests the bits
+ *    of the value. If ((FLAG & variable) == FLAG) then the string is
+ *    printed. If more than one flag matches, then each one that does is
+ *    also printed with delim in between them.
+ *    If not all bits are accounted for, then the not found bits will be
+ *    added in hex format: 0x506 will show BIT2|BIT4|0x500
+ */
+                  __print_flags(__entry->bar, "|",
+                                { 1, "BIT1" },
+                                { 2, "BIT2" },
+                                { 4, "BIT3" },
+                                { 8, "BIT4" }
+                          ),
+/*
+ *  __print_array( array, len, element_size )
+ *
+ *    This prints out the array that is defined by __array in a nice format.
+ */
+                  __print_array(__get_dynamic_array(list),
+                                __get_dynamic_array_len(list) / sizeof(int),
+                                sizeof(int)),
+                  __get_str(str), __get_bitmask(cpus))
+);
+
+/*
+ * There may be a case where a tracepoint should only be called if
+ * some condition is set. Otherwise the tracepoint should not be called.
+ * But to do something like:
+ *
+ *  if (cond)
+ *     trace_foo();
+ *
+ * Would cause a little overhead when tracing is not enabled, and that
+ * overhead, even if small, is not something we want. As tracepoints
+ * use static branch (aka jump_labels), where no branch is taken to
+ * skip the tracepoint when not enabled, and a jmp is placed to jump
+ * to the tracepoint code when it is enabled, having a if statement
+ * nullifies that optimization. It would be nice to place that
+ * condition within the static branch. This is where TRACE_EVENT_CONDITION
+ * comes in.
+ *
+ * TRACE_EVENT_CONDITION() is just like TRACE_EVENT, except it adds another
+ * parameter just after args. Where TRACE_EVENT has:
+ *
+ * TRACE_EVENT(name, proto, args, struct, assign, printk)
+ *
+ * the CONDITION version has:
+ *
+ * TRACE_EVENT_CONDITION(name, proto, args, cond, struct, assign, printk)
+ *
+ * Everything is the same as TRACE_EVENT except for the new cond. Think
+ * of the cond variable as:
+ *
+ *   if (cond)
+ *      trace_foo_bar_with_cond();
+ *
+ * Except that the logic for the if branch is placed after the static branch.
+ * That is, the if statement that processes the condition will not be
+ * executed unless that traecpoint is enabled. Otherwise it still remains
+ * a nop.
+ */
+TRACE_EVENT_CONDITION(foo_bar_with_cond,
+
+        TP_PROTO(const char *foo, int bar),
+
+        TP_ARGS(foo, bar),
+
+        TP_CONDITION(!(bar % 10)),
+
+        TP_STRUCT__entry(
+                __string(       foo,    foo             )
+                __field(        int,    bar                     )
+        ),
+
+        TP_fast_assign(
+                __assign_str(foo, foo);
+                __entry->bar    = bar;
+        ),
+
+        TP_printk("foo %s %d", __get_str(foo), __entry->bar)
+);
+
+int foo_bar_reg(void);
+void foo_bar_unreg(void);
+
+/*
+ * Now in the case that some function needs to be called when the
+ * tracepoint is enabled and/or when it is disabled, the
+ * TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT()
+ * but adds two more parameters at the end:
+ *
+ * TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg)
+ *
+ * reg and unreg are functions with the prototype of:
+ *
+ *    void reg(void)
+ *
+ * The reg function gets called before the tracepoint is enabled, and
+ * the unreg function gets called after the tracepoint is disabled.
+ *
+ * Note, reg and unreg are allowed to be NULL. If you only need to
+ * call a function before enabling, or after disabling, just set one
+ * function and pass in NULL for the other parameter.
+ */
+TRACE_EVENT_FN(foo_bar_with_fn,
+
+        TP_PROTO(const char *foo, int bar),
+
+        TP_ARGS(foo, bar),
+
+        TP_STRUCT__entry(
+                __string(       foo,    foo             )
+                __field(        int,    bar             )
+        ),
+
+        TP_fast_assign(
+                __assign_str(foo, foo);
+                __entry->bar    = bar;
+        ),
+
+        TP_printk("foo %s %d", __get_str(foo), __entry->bar),
+
+        foo_bar_reg, foo_bar_unreg
+);
+
+/*
+ * Each TRACE_EVENT macro creates several helper functions to produce
+ * the code to add the tracepoint, create the files in the trace
+ * directory, hook it to perf, assign the values and to print out
+ * the raw data from the ring buffer. To prevent too much bloat,
+ * if there are more than one tracepoint that uses the same format
+ * for the proto, args, struct, assign and printk, and only the name
+ * is different, it is highly recommended to use the DECLARE_EVENT_CLASS
+ *
+ * DECLARE_EVENT_CLASS() macro creates most of the functions for the
+ * tracepoint. Then DEFINE_EVENT() is use to hook a tracepoint to those
+ * functions. This DEFINE_EVENT() is an instance of the class and can
+ * be enabled and disabled separately from other events (either TRACE_EVENT
+ * or other DEFINE_EVENT()s).
+ *
+ * Note, TRACE_EVENT() itself is simply defined as:
+ *
+ * #define TRACE_EVENT(name, proto, args, tstruct, assign, printk)  \
+ *  DEFINE_EVENT_CLASS(name, proto, args, tstruct, assign, printk); \
+ *  DEFINE_EVENT(name, name, proto, args)
+ *
+ * The DEFINE_EVENT() also can be declared with conditions and reg functions:
+ *
+ * DEFINE_EVENT_CONDITION(template, name, proto, args, cond);
+ * DEFINE_EVENT_FN(template, name, proto, args, reg, unreg);
+ */
+DECLARE_EVENT_CLASS(foo_template,
+
+        TP_PROTO(const char *foo, int bar),
+
+        TP_ARGS(foo, bar),
+
+        TP_STRUCT__entry(
+                __string(       foo,    foo             )
+                __field(        int,    bar             )
+        ),
+
+        TP_fast_assign(
+                __assign_str(foo, foo);
+                __entry->bar    = bar;
+        ),
+
+        TP_printk("foo %s %d", __get_str(foo), __entry->bar)
+);
+
+/*
+ * Here's a better way for the previous samples (except, the first
+ * exmaple had more fields and could not be used here).
+ */
+DEFINE_EVENT(foo_template, foo_with_template_simple,
+        TP_PROTO(const char *foo, int bar),
+        TP_ARGS(foo, bar));
+
+DEFINE_EVENT_CONDITION(foo_template, foo_with_template_cond,
+        TP_PROTO(const char *foo, int bar),
+        TP_ARGS(foo, bar),
+        TP_CONDITION(!(bar % 8)));
+
+
+DEFINE_EVENT_FN(foo_template, foo_with_template_fn,
+        TP_PROTO(const char *foo, int bar),
+        TP_ARGS(foo, bar),
+        foo_bar_reg, foo_bar_unreg);
+
+/*
+ * Anytime two events share basically the same values and have
+ * the same output, use the DECLARE_EVENT_CLASS() and DEFINE_EVENT()
+ * when ever possible.
+ */
+
+/*
+ * If the event is similar to the DECLARE_EVENT_CLASS, but you need
+ * to have a different output, then use DEFINE_EVENT_PRINT() which
+ * lets you override the TP_printk() of the class.
+ */
+
+DEFINE_EVENT_PRINT(foo_template, foo_with_template_print,
+        TP_PROTO(const char *foo, int bar),
+        TP_ARGS(foo, bar),
+        TP_printk("bar %s %d", __get_str(foo), __entry->bar));
+
+#endif
+
+/***** NOTICE! The #if protection ends here. *****/
+
+
+/*
+ * There are several ways I could have done this. If I left out the
+ * TRACE_INCLUDE_PATH, then it would default to the kernel source
+ * include/trace/events directory.
+ *
+ * I could specify a path from the define_trace.h file back to this
+ * file.
+ *
+ * #define TRACE_INCLUDE_PATH ../../samples/trace_events
+ *
+ * But the safest and easiest way to simply make it use the directory
+ * that the file is in is to add in the Makefile:
+ *
+ * CFLAGS_trace-events-sample.o := -I$(src)
+ *
+ * This will make sure the current path is part of the include
+ * structure for our file so that define_trace.h can find it.
+ *
+ * I could have made only the top level directory the include:
+ *
+ * CFLAGS_trace-events-sample.o := -I$(PWD)
+ *
+ * And then let the path to this directory be the TRACE_INCLUDE_PATH:
+ *
+ * #define TRACE_INCLUDE_PATH samples/trace_events
+ *
+ * But then if something defines "samples" or "trace_events" as a macro
+ * then we could risk that being converted too, and give us an unexpected
+ * result.
+ */
+#undef TRACE_INCLUDE_PATH
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_PATH .
+/*
+ * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal
+ */
+#define TRACE_INCLUDE_FILE trace-events-sample
+#include <trace/define_trace.h>
diff --git a/study/kernel/head.h b/study/kernel/head.h
new file mode 100644
index 0000000..f609700
--- /dev/null
+++ b/study/kernel/head.h
@@ -0,0 +1,95 @@
+//  http://www.cnblogs.com/chen-farsight/p/6146168.html
+
+Linux驱动开发常用头文件
+
+头文件目录中总共有32个.h头文件。其中主目录下有13个，asm子目录中有4个，linux子目录中有10个，sys子目录中有5个。这些头文件各自的功能如下：
+
+1、主目录
+
+<a.out.h>：a.out头文件，定义了a.out执行文件格式和一些宏。
+<const.h>：常数符号头文件，目前仅定义了i节点中i_mode字段的各标志位。
+<ctype.h>：字符类型头文件，定义了一些有关字符类型判断和转换的宏。
+<errno.h>：错误号头文件，包含系统中各种出错号。(Linus从minix中引进的)。
+<fcntl.h>：文件控制头文件，用于文件及其描述符的操作控制常数符号的定义。
+<signal.h>：信号头文件，定义信号符号常量，信号结构以及信号操作函数原型。
+<stdarg.h>：标准参数头文件，以宏的形式定义变量参数列表。主要说明了一个类型（va_list）和3个宏（va_start, va_arg和va_end），用于vsprintf、vprintf、vfprintf函数。
+<stddef.h>：标准定义头文件，定义了NULL, offsetof(TYPE, MEMBER)。
+<string.h>：字符串头文件，主要定义了一些有关字符串操作的嵌入函数。
+<termios.h>：终端输入输出函数头文件，主要定义控制异步通信口的终端接口。
+<time.h>：时间类型头文件，主要定义了tm结构和一些有关时间的函数原形。
+<unistd.h>：Linux标准头文件，定义了各种符号常数和类型，并声明了各种函数。如，定义了__LIBRARY__，则还包括系统调用号和内嵌汇编_syscall0()等。
+<utime.h>：用户时间头文件，定义了访问和修改时间结构以及utime()原型。
+
+2、体系结构相关头文件子目录include/asm
+
+这些头文件主要定义了一些与CPU体系结构密切相关的数据结构、宏函数和变量。共4个文件。
+<asm/io.h>：I/O头文件，以宏的嵌入汇编程序形式定义对I/O端口操作的函数。
+<asm/memory.h>：内存拷贝头文件，含有memcpy()嵌入式汇编宏函数。
+<asm/segment.h>：段操作头文件，定义了有关段寄存器操作的嵌入式汇编函数。
+<asm/system.h>：系统头文件，定义了设置或修改描述符/中断门等的嵌入式汇编宏。
+
+3、Linux内核专用头文件子目录include/linux
+
+<linux/config.h>：内核配置头文件，定义键盘语言和硬盘类型（HD_TYPE）可选项。
+<linux/fdreg.h>：软驱头文件，含有软盘控制器参数的一些定义。
+<linux/fs.h>：文件系统头文件，定义文件表结构（file,buffer_head,m_inode等）。
+<linux/hdreg.h>：硬盘参数头文件，定义访问硬盘寄存器端口、状态码和分区表等信息。
+<linux/head.h>：head头文件，定义了段描述符的简单结构，和几个选择符常量。
+<linux/kernel.h>：内核头文件，含有一些内核常用函数的原形定义。
+<linux/mm.h>：内存管理头文件，含有页面大小定义和一些页面释放函数原型。
+<linux/sched.h>： 调度程序头文件，定义了任务结构task_struct、初始任务0的数据，以及一些有关描述符参数设置和获取的嵌入式汇编函数宏语句。
+<linux/sys.h>：系统调用头文件，含有72个系统调用C函数处理程序,以"sys_"开头。
+<linux/tty.h>：tty头文件，定义了有关tty_io，串行通信方面的参数、常数。
+
+4、系统专用数据结构子目录include/sys
+
+<sys/stat.h>： 文件状态头文件，含有文件或文件系统状态结构stat{}和常量。
+<sys/times.h>：定义了进程中运行时间结构tms以及times()函数原型。
+<sys/types.h>：类型头文件，定义了基本的系统数据类型。
+<sys/utsname.h>：系统名称结构头文件。
+<sys/wait.h>：等待调用头文件，定义系统调用wait()和waitpid()及相关常数符号。
+
+
+
+#include <Linux/***.h>                     //是在linux-2.6.29/include/linux下面寻找源文件。
+#include <asm/***.h>                     //是在linux-2.6.29/arch/arm/include/asm下面寻找源文件。
+#include <mach/***.h>                   //是在linux-2.6.29/arch/arm/mach-s3c2410/include/mach下面寻找源文件。
+#include <plat/regs-adc.h>           //在linux-2.6.31_TX2440A20100510\linux-2.6.31_TX2440A\arch\arm\plat-s3c\include\plat
+#include <linux/module.h>            //最基本的文件，支持动态添加和卸载模块。Hello World驱动要这一个文件就可以了
+#include <linux/fs.h>                       //包含了文件操作相关struct的定义，例如大名鼎鼎的struct file_operations，包含了struct inode 的定义，MINOR、MAJOR的头文件。
+#include <linux/errno.h>                 //包含了对返回值的宏定义，这样用户程序可以用perror输出错误信息。
+#include <linux/types.h>                 //对一些特殊类型的定义，例如dev_t, off_t, pid_t.其实这些类型大部分都是unsigned int型通过一连串的typedef变过来的，只是为了方便阅读。
+#include <linux/cdev.h>                  //对字符设备结构cdev以及一系列的操作函数的定义。//包含了cdev 结构及相关函数的定义。
+#include <linux/wait.h>                   //等代队列相关头文件//内核等待队列，它包含了自旋锁的头文件
+#include <linux/init.h>                     //初始化头文件
+#include <linux/kernel.h>               //驱动要写入内核，与内核相关的头文件
+#include <linux/slab.h>                   //包含了kcalloc、kzalloc内存分配函数的定义。
+#include <linux/uaccess.h>           //包含了copy_to_user、copy_from_user等内核访问用户进程内存地址的函数定义。
+#include <linux/device.h>               //包含了device、class 等结构的定义
+#include <linux/io.h>                       //包含了ioremap、iowrite等内核访问IO内存等函数的定义。
+#include <linux/miscdevice.h>      //包含了miscdevice结构的定义及相关的操作函数。
+#include <linux/interrupt.h>            //使用中断必须的头文件
+#include <mach/irqs.h>                  //使用中断必须的头文件
+#include <asm/bitops.h>                //包含set_bit等位操作函数，实现Input子系统时可用。
+#include <linux/semaphore.h>      //使用信号量必须的头文件
+#include <linux/spinlock.h>            //自旋锁
+#include <linux/sched.h>                //内核等待队列中要使用的TASK_NORMAL、TASK_INTERRUPTIBLE包含在这个头文件
+#include <linux/kfifo.h>                    //fifo环形队列
+#include <linux/timer.h>                  //内核定时器
+#include<linux/input.h>                   //中断处理
+#include <linux/delay.h>                  //延时头文件
+#include <asm/irq.h>                       //与处理器相关的中断
+#include<linux/interrupt.h>              //操作系统中断
+#include <asm/uaccess.h>            //与处理器相关的入口
+#include<asm/arch/regs-gpio.h>  //与处理器相关的IO口操作
+#include<mach/regs-gpio.h>         //同上
+#include<asm/hardware.h>           //与处理器相关的硬件
+#include<mach/hardware.h>          //同上
+#include <linux/poll.h>                      //轮询文件
+#include <linux/gpio.h>                     //操作系统相关的IO口文件
+#include <stdio.h>                             //标准输入输出
+#include <stdlib.h>                            //标准库
+#include <unistd.h>                           //Unix标准
+#include <sys/ioctl.h>                       //IO控制
+
+分类: Linux设备驱动开发