tracing/ftrace: make nop tracer using tracer flags

#include "trace.h"

/* Our two options */

enum {

	TRACE_NOP_OPT_ACCEPT = 0x1,

	TRACE_NOP_OPT_REFUSE = 0x2

};

/* Options for the tracer (see trace_options file) */

static struct tracer_opt nop_opts[] = {

	/* Option that will be accepted by set_flag callback */

	{ TRACER_OPT(test_nop_accept, TRACE_NOP_OPT_ACCEPT) },

	/* Option that will be refused by set_flag callback */

	{ TRACER_OPT(test_nop_refuse, TRACE_NOP_OPT_REFUSE) },

	{ } /* Always set a last empty entry */

};

static struct tracer_flags nop_flags = {

	/* You can check your flags value here when you want. */

	.val = 0, /* By default: all flags disabled */

	.opts = nop_opts

};

static struct trace_array	*ctx_trace;

static void start_nop_trace(struct trace_array *tr)

	stop_nop_trace(tr);

}

/* It only serves as a signal handler and a callback to

 * accept or refuse tthe setting of a flag.

 * If you don't implement it, then the flag setting will be

 * automatically accepted.

 */

static int nop_set_flag(u32 old_flags, u32 bit, int set)

{

	/*

	 * Note that you don't need to update nop_flags.val yourself.

	 * The tracing Api will do it automatically if you return 0

	 */

	if (bit == TRACE_NOP_OPT_ACCEPT) {

		printk(KERN_DEBUG "nop_test_accept flag set to %d: we accept."

			" Now cat trace_options to see the result\n",

			set);

		return 0;

	}

	if (bit == TRACE_NOP_OPT_REFUSE) {

		printk(KERN_DEBUG "nop_test_refuse flag set to %d: we refuse."

			"Now cat trace_options to see the result\n",

			set);

		return -EINVAL;

	}

	return 0;

}

struct tracer nop_trace __read_mostly =

{

	.name		= "nop",

#ifdef CONFIG_FTRACE_SELFTEST

	.selftest	= trace_selftest_startup_nop,

#endif

	.flags		= &nop_flags,

	.set_flag	= nop_set_flag

};