/*
 * Copyright (C) 2010 Michael Hennerich, Analog Devices Inc.
 * Copyright (C) 2008-2010 Jonathan Cameron
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * ad799x_ring.c
 */

#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/sysfs.h>
#include <linux/list.h>
#include <linux/i2c.h>
#include <linux/bitops.h>

#include "../iio.h"
#include "../ring_generic.h"
#include "../ring_sw.h"
#include "../trigger.h"
#include "../sysfs.h"

#include "ad799x.h"

int ad799x_single_channel_from_ring(struct ad799x_state *st, long mask)
{
	struct iio_ring_buffer *ring = st->indio_dev->ring;
	int count = 0, ret;
	u16 *ring_data;

	if (!(ring->scan_mask & mask)) {
		ret = -EBUSY;
		goto error_ret;
	}

	ring_data = kmalloc(ring->access.get_bytes_per_datum(ring), GFP_KERNEL);
	if (ring_data == NULL) {
		ret = -ENOMEM;
		goto error_ret;
	}
	ret = ring->access.read_last(ring, (u8 *) ring_data);
	if (ret)
		goto error_free_ring_data;
	/* Need a count of channels prior to this one */
	mask >>= 1;
	while (mask) {
		if (mask & ring->scan_mask)
			count++;
		mask >>= 1;
	}

	ret = be16_to_cpu(ring_data[count]);

error_free_ring_data:
	kfree(ring_data);
error_ret:
	return ret;
}

/**
 * ad799x_ring_preenable() setup the parameters of the ring before enabling
 *
 * The complex nature of the setting of the nuber of bytes per datum is due
 * to this driver currently ensuring that the timestamp is stored at an 8
 * byte boundary.
 **/
static int ad799x_ring_preenable(struct iio_dev *indio_dev)
{
	struct iio_ring_buffer *ring = indio_dev->ring;
	struct ad799x_state *st = indio_dev->dev_data;

	/*
	 * Need to figure out the current mode based upon the requested
	 * scan mask in iio_dev
	 */

	if (st->id == ad7997 || st->id == ad7998)
		ad799x_set_scan_mode(st, ring->scan_mask);

	st->d_size = ring->scan_count * 2;

	if (ring->scan_timestamp) {
		st->d_size += sizeof(s64);

		if (st->d_size % sizeof(s64))
			st->d_size += sizeof(s64) - (st->d_size % sizeof(s64));
	}

	if (indio_dev->ring->access.set_bytes_per_datum)
		indio_dev->ring->access.set_bytes_per_datum(indio_dev->ring,
							    st->d_size);

	return 0;
}

/**
 * ad799x_poll_func_th() th of trigger launched polling to ring buffer
 *
 * As sampling only occurs on i2c comms occuring, leave timestamping until
 * then.  Some triggers will generate their own time stamp.  Currently
 * there is no way of notifying them when no one cares.
 **/
static void ad799x_poll_func_th(struct iio_dev *indio_dev, s64 time)
{
	struct ad799x_state *st = indio_dev->dev_data;

	schedule_work(&st->poll_work);

	return;
}
/**
 * ad799x_poll_bh_to_ring() bh of trigger launched polling to ring buffer
 * @work_s:	the work struct through which this was scheduled
 *
 * Currently there is no option in this driver to disable the saving of
 * timestamps within the ring.
 * I think the one copy of this at a time was to avoid problems if the
 * trigger was set far too high and the reads then locked up the computer.
 **/
static void ad799x_poll_bh_to_ring(struct work_struct *work_s)
{
	struct ad799x_state *st = container_of(work_s, struct ad799x_state,
						  poll_work);
	struct iio_dev *indio_dev = st->indio_dev;
	struct iio_ring_buffer *ring = indio_dev->ring;
	struct iio_sw_ring_buffer *ring_sw = iio_to_sw_ring(indio_dev->ring);
	s64 time_ns;
	__u8 *rxbuf;
	int b_sent;
	u8 cmd;

	/* Ensure only one copy of this function running at a time */
	if (atomic_inc_return(&st->protect_ring) > 1)
		return;

	rxbuf = kmalloc(st->d_size, GFP_KERNEL);
	if (rxbuf == NULL)
		return;

	switch (st->id) {
	case ad7991:
	case ad7995:
	case ad7999:
		cmd = st->config | (ring->scan_mask << AD799X_CHANNEL_SHIFT);
		break;
	case ad7992:
	case ad7993:
	case ad7994:
		cmd = (ring->scan_mask << AD799X_CHANNEL_SHIFT) |
			AD7998_CONV_RES_REG;
		break;
	case ad7997:
	case ad7998:
		cmd = AD7997_8_READ_SEQUENCE | AD7998_CONV_RES_REG;
		break;
	default:
		cmd = 0;
	}

	b_sent = i2c_smbus_read_i2c_block_data(st->client,
			cmd, ring->scan_count * 2, rxbuf);
	if (b_sent < 0)
		goto done;

	time_ns = iio_get_time_ns();

	if (ring->scan_timestamp)
		memcpy(rxbuf + st->d_size - sizeof(s64),
			&time_ns, sizeof(time_ns));

	ring->access.store_to(&ring_sw->buf, rxbuf, time_ns);
done:
	kfree(rxbuf);
	atomic_dec(&st->protect_ring);
}


int ad799x_register_ring_funcs_and_init(struct iio_dev *indio_dev)
{
	struct ad799x_state *st = indio_dev->dev_data;
	int ret = 0;

	indio_dev->ring = iio_sw_rb_allocate(indio_dev);
	if (!indio_dev->ring) {
		ret = -ENOMEM;
		goto error_ret;
	}
	/* Effectively select the ring buffer implementation */
	iio_ring_sw_register_funcs(&st->indio_dev->ring->access);
	ret = iio_alloc_pollfunc(indio_dev, NULL, &ad799x_poll_func_th);
	if (ret)
		goto error_deallocate_sw_rb;

	/* Ring buffer functions - here trigger setup related */

	indio_dev->ring->preenable = &ad799x_ring_preenable;
	indio_dev->ring->postenable = &iio_triggered_ring_postenable;
	indio_dev->ring->predisable = &iio_triggered_ring_predisable;
	indio_dev->ring->scan_timestamp = true;

	INIT_WORK(&st->poll_work, &ad799x_poll_bh_to_ring);

	indio_dev->ring->scan_el_attrs = st->chip_info->scan_attrs;

	/* Flag that polled ring buffering is possible */
	indio_dev->modes |= INDIO_RING_TRIGGERED;
	return 0;
error_deallocate_sw_rb:
	iio_sw_rb_free(indio_dev->ring);
error_ret:
	return ret;
}

void ad799x_ring_cleanup(struct iio_dev *indio_dev)
{
	/* ensure that the trigger has been detached */
	if (indio_dev->trig) {
		iio_put_trigger(indio_dev->trig);
		iio_trigger_dettach_poll_func(indio_dev->trig,
					      indio_dev->pollfunc);
	}
	kfree(indio_dev->pollfunc);
	iio_sw_rb_free(indio_dev->ring);
}