/*
 * 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;
        size_t d_size;
        unsigned long numvals;

        /*
         * 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);

        numvals = ring->scan_count;

        if (ring->access.set_bytes_per_datum) {
                d_size = numvals*2 + sizeof(s64);
                if (d_size % 8)
                        d_size += 8 - (d_size % 8);
                ring->access.set_bytes_per_datum(ring, 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;
        size_t d_size;
        u8 cmd;

        unsigned long numvals = ring->scan_count;

        /* Ensure the timestamp is 8 byte aligned */
        d_size = numvals*2 + sizeof(s64);

        if (d_size % sizeof(s64))
                d_size += sizeof(s64) - (d_size % sizeof(s64));

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

        /* Monitor mode prevents reading. Whilst not currently implemented
         * might as well have this test in here in the meantime as it does
         * no harm.
         */
        if (numvals == 0)
                return;

        rxbuf = kmalloc(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, numvals*2, rxbuf);
        if (b_sent < 0)
                goto done;

        time_ns = iio_get_time_ns();

        memcpy(rxbuf + 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;

        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);
}