iio_simple_dummy_buffer.c

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#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,
};
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;
    struct iio_buffer *buffer = indio_dev->buffer;
    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(buffer->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_buffer(buffer, (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 top 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;

}

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);
}