#include <linux/sched.h>
#include <linux/module.h>
#include <linux/uaccess.h>

#include <litmus/ftdev.h>
#include <litmus/litmus.h>
#include <litmus/trace.h>

/******************************************************************************/
/*                          Allocation                                        */
/******************************************************************************/

static struct ftdev overhead_dev;

#define trace_ts_buf overhead_dev.minor[0].buf

static unsigned int ts_seq_no = 0;

static inline void __save_timestamp_cpu(unsigned long event,
					uint8_t type, uint8_t cpu)
{
	unsigned int seq_no;
	struct timestamp *ts;
	seq_no = fetch_and_inc((int *) &ts_seq_no);
	if (ft_buffer_start_write(trace_ts_buf, (void**)  &ts)) {
		ts->event     = event;
		ts->timestamp = ft_timestamp();
		ts->seq_no    = seq_no;
		ts->cpu       = cpu;
		ts->task_type = type;
		ft_buffer_finish_write(trace_ts_buf, ts);
	}
}

static void __add_timestamp_user(struct timestamp *pre_recorded)
{
	unsigned int seq_no;
	struct timestamp *ts;
	seq_no = fetch_and_inc((int *) &ts_seq_no);

	if (ft_buffer_start_write(trace_ts_buf, (void**)  &ts)) {
		*ts = *pre_recorded;
		ts->seq_no = seq_no;
		ft_buffer_finish_write(trace_ts_buf, ts);
	}
}

static inline void __save_timestamp(unsigned long event,
				   uint8_t type)
{
	__save_timestamp_cpu(event, type, raw_smp_processor_id());
}

/* hack: fake timestamp to user-reported time, and record parts of the PID */
feather_callback void save_timestamp_time(unsigned long event, unsigned long ptr)
{
	uint64_t* time = (uint64_t*) ptr;
	unsigned int seq_no;
	struct timestamp *ts;
	seq_no = fetch_and_inc((int *) &ts_seq_no);
	if (ft_buffer_start_write(trace_ts_buf, (void**)  &ts)) {
		ts->event     = event;
		ts->timestamp = *time;
		ts->seq_no    = seq_no;
		/* type takes lowest byte of PID */
		ts->task_type = (uint8_t) current->pid;
		/* cpu takes second-lowest byte of PID*/
		ts->cpu       = (uint8_t) (current->pid >> 8);

		ft_buffer_finish_write(trace_ts_buf, ts);
	}
}

feather_callback void save_timestamp_pid(unsigned long event)
{
	/* Abuse existing fields to partially export PID. */
	__save_timestamp_cpu(event,
			     /* type takes lowest byte of PID */
			     (uint8_t) current->pid,
			     /* cpu takes second-lowest byte of PID*/
			     (uint8_t) (current->pid >> 8));
}

feather_callback void save_timestamp(unsigned long event)
{
	__save_timestamp(event, TSK_UNKNOWN);
}

feather_callback void save_timestamp_def(unsigned long event,
					 unsigned long type)
{
	__save_timestamp(event, (uint8_t) type);
}

feather_callback void save_timestamp_task(unsigned long event,
					  unsigned long t_ptr)
{
	int rt = is_realtime((struct task_struct *) t_ptr);
	__save_timestamp(event, rt ? TSK_RT : TSK_BE);
}

feather_callback void save_timestamp_cpu(unsigned long event,
					 unsigned long cpu)
{
	__save_timestamp_cpu(event, TSK_UNKNOWN, cpu);
}

feather_callback void save_task_latency(unsigned long event,
					unsigned long when_ptr)
{
	lt_t now = litmus_clock();
	lt_t *when = (lt_t*) when_ptr;
	unsigned int seq_no;
	int cpu = raw_smp_processor_id();
	struct timestamp *ts;

	seq_no = fetch_and_inc((int *) &ts_seq_no);
	if (ft_buffer_start_write(trace_ts_buf, (void**)  &ts)) {
		ts->event     = event;
		ts->timestamp = now - *when;
		ts->seq_no    = seq_no;
		ts->cpu       = cpu;
		ts->task_type = TSK_RT;
		ft_buffer_finish_write(trace_ts_buf, ts);
	}
}

/******************************************************************************/
/*                        DEVICE FILE DRIVER                                  */
/******************************************************************************/

/*
 * should be 8M; it is the max we can ask to buddy system allocator (MAX_ORDER)
 * and we might not get as much
 */
#define NO_TIMESTAMPS (2 << 16)

static int alloc_timestamp_buffer(struct ftdev* ftdev, unsigned int idx)
{
	unsigned int count = NO_TIMESTAMPS;
	while (count && !trace_ts_buf) {
		printk("time stamp buffer: trying to allocate %u time stamps.\n", count);
		ftdev->minor[idx].buf = alloc_ft_buffer(count, sizeof(struct timestamp));
		count /= 2;
	}
	return ftdev->minor[idx].buf ? 0 : -ENOMEM;
}

static void free_timestamp_buffer(struct ftdev* ftdev, unsigned int idx)
{
	free_ft_buffer(ftdev->minor[idx].buf);
	ftdev->minor[idx].buf = NULL;
}

static ssize_t write_timestamp_from_user(struct ft_buffer* buf, size_t len,
					 const char __user *from)
{
	ssize_t consumed = 0;
	struct timestamp ts;

	/* don't give us partial timestamps */
	if (len % sizeof(ts))
		return -EINVAL;

	while (len >= sizeof(ts)) {
		if (copy_from_user(&ts, from, sizeof(ts))) {
			consumed = -EFAULT;
			goto out;
		}
		len  -= sizeof(ts);
		from += sizeof(ts);
		consumed += sizeof(ts);

		__add_timestamp_user(&ts);
	}

out:
	return consumed;
}

static int __init init_ft_overhead_trace(void)
{
	int err;

	printk("Initializing Feather-Trace overhead tracing device.\n");
	err = ftdev_init(&overhead_dev, THIS_MODULE, 1, "ft_trace");
	if (err)
		goto err_out;

	overhead_dev.alloc = alloc_timestamp_buffer;
	overhead_dev.free  = free_timestamp_buffer;
	overhead_dev.write = write_timestamp_from_user;

	err = register_ftdev(&overhead_dev);
	if (err)
		goto err_dealloc;

	return 0;

err_dealloc:
	ftdev_exit(&overhead_dev);
err_out:
	printk(KERN_WARNING "Could not register ft_trace module.\n");
	return err;
}

static void __exit exit_ft_overhead_trace(void)
{
	ftdev_exit(&overhead_dev);
}

module_init(init_ft_overhead_trace);
module_exit(exit_ft_overhead_trace);