/**
 * Copyright (c) 2011 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.
 *
 * Buffer handling elements of industrial I/O reference driver.
 * Uses the kfifo buffer.
 *
 * To test without hardware use the sysfs trigger.
 */

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/bitmap.h>

#include <linux/iio/iio.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/kfifo_buf.h>

#include "iio_simple_dummy.h"

/* Some fake data */

static const s16 fakedata[] = {
        [voltage0] = 7,
        [diffvoltage1m2] = -33,
        [diffvoltage3m4] = -2,
        [accelx] = 344,
};
/**
 * iio_simple_dummy_trigger_h() - the trigger handler function
 * @irq: the interrupt number
 * @p: private data - always a pointer to the poll func.
 *
 * This is the guts of buffered capture. On a trigger event occurring,
 * if the pollfunc is attached then this handler is called as a threaded
 * interrupt (and hence may sleep). It is responsible for grabbing data
 * from the device and pushing it into the associated buffer.
 */
static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
{
        struct iio_poll_func *pf = p;
        struct iio_dev *indio_dev = pf->indio_dev;
        int len = 0;
        u16 *data;

        data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
        if (data == NULL)
                goto done;

        if (!bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength)) {
                /*
                 * Three common options here:
                 * hardware scans: certain combinations of channels make
                 *   up a fast read.  The capture will consist of all of them.
                 *   Hence we just call the grab data function and fill the
                 *   buffer without processing.
                 * software scans: can be considered to be random access
                 *   so efficient reading is just a case of minimal bus
                 *   transactions.
                 * software culled hardware scans:
                 *   occasionally a driver may process the nearest hardware
                 *   scan to avoid storing elements that are not desired. This
                 *   is the fiddliest option by far.
                 * Here let's pretend we have random access. And the values are
                 * in the constant table fakedata.
                 */
                int i, j;
                for (i = 0, j = 0;
                     i < bitmap_weight(indio_dev->active_scan_mask,
                                       indio_dev->masklength);
                     i++, j++) {
                        j = find_next_bit(indio_dev->active_scan_mask,
                                          indio_dev->masklength, j);
                        /* random access read from the 'device' */
                        data[i] = fakedata[j];
                        len += 2;
                }
        }
        /* Store the timestamp at an 8 byte aligned offset */
        if (indio_dev->scan_timestamp)
                *(s64 *)((u8 *)data + ALIGN(len, sizeof(s64)))
                        = iio_get_time_ns();
        iio_push_to_buffers(indio_dev, (u8 *)data);

        kfree(data);

done:
        /*
         * Tell the core we are done with this trigger and ready for the
         * next one.
         */
        iio_trigger_notify_done(indio_dev->trig);

        return IRQ_HANDLED;
}

static const struct iio_buffer_setup_ops iio_simple_dummy_buffer_setup_ops = {
        /*
         * iio_sw_buffer_preenable:
         * Generic function for equal sized ring elements + 64 bit timestamp
         * Assumes that any combination of channels can be enabled.
         * Typically replaced to implement restrictions on what combinations
         * can be captured (hardware scan modes).
         */
        .preenable = &iio_sw_buffer_preenable,
        /*
         * iio_triggered_buffer_postenable:
         * Generic function that simply attaches the pollfunc to the trigger.
         * Replace this to mess with hardware state before we attach the
         * trigger.
         */
        .postenable = &iio_triggered_buffer_postenable,
        /*
         * iio_triggered_buffer_predisable:
         * Generic function that simple detaches the pollfunc from the trigger.
         * Replace this to put hardware state back again after the trigger is
         * detached but before userspace knows we have disabled the ring.
         */
        .predisable = &iio_triggered_buffer_predisable,
};

int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev,
        const struct iio_chan_spec *channels, unsigned int num_channels)
{
        int ret;
        struct iio_buffer *buffer;

        /* Allocate a buffer to use - here a kfifo */
        buffer = iio_kfifo_allocate(indio_dev);
        if (buffer == NULL) {
                ret = -ENOMEM;
                goto error_ret;
        }

        indio_dev->buffer = buffer;

        /* Enable timestamps by default */
        buffer->scan_timestamp = true;

        /*
         * Tell the core what device type specific functions should
         * be run on either side of buffer capture enable / disable.
         */
        indio_dev->setup_ops = &iio_simple_dummy_buffer_setup_ops;

        /*
         * Configure a polling function.
         * When a trigger event with this polling function connected
         * occurs, this function is run. Typically this grabs data
         * from the device.
         *
         * NULL for the bottom half. This is normally implemented only if we
         * either want to ping a capture now pin (no sleeping) or grab
         * a timestamp as close as possible to a data ready trigger firing.
         *
         * IRQF_ONESHOT ensures irqs are masked such that only one instance
         * of the handler can run at a time.
         *
         * "iio_simple_dummy_consumer%d" formatting string for the irq 'name'
         * as seen under /proc/interrupts. Remaining parameters as per printk.
         */
        indio_dev->pollfunc = iio_alloc_pollfunc(NULL,
                                                 &iio_simple_dummy_trigger_h,
                                                 IRQF_ONESHOT,
                                                 indio_dev,
                                                 "iio_simple_dummy_consumer%d",
                                                 indio_dev->id);

        if (indio_dev->pollfunc == NULL) {
                ret = -ENOMEM;
                goto error_free_buffer;
        }

        /*
         * Notify the core that this device is capable of buffered capture
         * driven by a trigger.
         */
        indio_dev->modes |= INDIO_BUFFER_TRIGGERED;

        ret = iio_buffer_register(indio_dev, channels, num_channels);
        if (ret)
                goto error_dealloc_pollfunc;

        return 0;

error_dealloc_pollfunc:
        iio_dealloc_pollfunc(indio_dev->pollfunc);
error_free_buffer:
        iio_kfifo_free(indio_dev->buffer);
error_ret:
        return ret;

}

/**
 * iio_simple_dummy_unconfigure_buffer() - release buffer resources
 * @indo_dev: device instance state
 */
void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
{
        iio_buffer_unregister(indio_dev);
        iio_dealloc_pollfunc(indio_dev->pollfunc);
        iio_kfifo_free(indio_dev->buffer);
}