kfifo_buf.c

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#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/workqueue.h>
#include <linux/kfifo.h>
#include <linux/mutex.h>
#include <linux/iio/kfifo_buf.h>
#include <linux/sched.h>

struct iio_kfifo {
    struct iio_buffer buffer;
    struct kfifo kf;
    int update_needed;
};

#define iio_to_kfifo(r) container_of(r, struct iio_kfifo, buffer)

static inline int __iio_allocate_kfifo(struct iio_kfifo *buf,
                int bytes_per_datum, int length)
{
    if ((length == 0) || (bytes_per_datum == 0))
        return -EINVAL;

    __iio_update_buffer(&buf->buffer, bytes_per_datum, length);
    return __kfifo_alloc((struct __kfifo *)&buf->kf, length,
                 bytes_per_datum, GFP_KERNEL);
}

static int iio_request_update_kfifo(struct iio_buffer *r)
{
    int ret = 0;
    struct iio_kfifo *buf = iio_to_kfifo(r);

    if (!buf->update_needed)
        goto error_ret;
    kfifo_free(&buf->kf);
    ret = __iio_allocate_kfifo(buf, buf->buffer.bytes_per_datum,
                   buf->buffer.length);
    r->stufftoread = false;
error_ret:
    return ret;
}

static int iio_get_length_kfifo(struct iio_buffer *r)
{
    return r->length;
}

static IIO_BUFFER_ENABLE_ATTR;
static IIO_BUFFER_LENGTH_ATTR;

static struct attribute *iio_kfifo_attributes[] = {
    &dev_attr_length.attr,
    &dev_attr_enable.attr,
    NULL,
};

static struct attribute_group iio_kfifo_attribute_group = {
    .attrs = iio_kfifo_attributes,
    .name = "buffer",
};

static int iio_get_bytes_per_datum_kfifo(struct iio_buffer *r)
{
    return r->bytes_per_datum;
}

static int iio_mark_update_needed_kfifo(struct iio_buffer *r)
{
    struct iio_kfifo *kf = iio_to_kfifo(r);
    kf->update_needed = true;
    return 0;
}

static int iio_set_bytes_per_datum_kfifo(struct iio_buffer *r, size_t bpd)
{
    if (r->bytes_per_datum != bpd) {
        r->bytes_per_datum = bpd;
        iio_mark_update_needed_kfifo(r);
    }
    return 0;
}

static int iio_set_length_kfifo(struct iio_buffer *r, int length)
{
    /* Avoid an invalid state */
    if (length < 2)
        length = 2;
    if (r->length != length) {
        r->length = length;
        iio_mark_update_needed_kfifo(r);
    }
    return 0;
}

static int iio_store_to_kfifo(struct iio_buffer *r,
                  u8 *data)
{
    int ret;
    struct iio_kfifo *kf = iio_to_kfifo(r);
    ret = kfifo_in(&kf->kf, data, 1);
    if (ret != 1)
        return -EBUSY;
    r->stufftoread = true;
    wake_up_interruptible(&r->pollq);

    return 0;
}

static int iio_read_first_n_kfifo(struct iio_buffer *r,
               size_t n, char __user *buf)
{
    int ret, copied;
    struct iio_kfifo *kf = iio_to_kfifo(r);

    if (n < r->bytes_per_datum || r->bytes_per_datum == 0)
        return -EINVAL;

    ret = kfifo_to_user(&kf->kf, buf, n, &copied);
    if (ret < 0)
        return ret;

    if (kfifo_is_empty(&kf->kf))
        r->stufftoread = false;
    /* verify it is still empty to avoid race */
    if (!kfifo_is_empty(&kf->kf))
        r->stufftoread = true;

    return copied;
}

static const struct iio_buffer_access_funcs kfifo_access_funcs = {
    .store_to = &iio_store_to_kfifo,
    .read_first_n = &iio_read_first_n_kfifo,
    .request_update = &iio_request_update_kfifo,
    .get_bytes_per_datum = &iio_get_bytes_per_datum_kfifo,
    .set_bytes_per_datum = &iio_set_bytes_per_datum_kfifo,
    .get_length = &iio_get_length_kfifo,
    .set_length = &iio_set_length_kfifo,
};

struct iio_buffer *iio_kfifo_allocate(struct iio_dev *indio_dev)
{
    struct iio_kfifo *kf;

    kf = kzalloc(sizeof *kf, GFP_KERNEL);
    if (!kf)
        return NULL;
    kf->update_needed = true;
    iio_buffer_init(&kf->buffer);
    kf->buffer.attrs = &iio_kfifo_attribute_group;
    kf->buffer.access = &kfifo_access_funcs;
    kf->buffer.length = 2;
    return &kf->buffer;
}
EXPORT_SYMBOL(iio_kfifo_allocate);

void iio_kfifo_free(struct iio_buffer *r)
{
    kfree(iio_to_kfifo(r));
}
EXPORT_SYMBOL(iio_kfifo_free);

MODULE_LICENSE("GPL");