kernel-ark/drivers/iio/kfifo_buf.c
Lars-Peter Clausen 355c1a14d4 iio: kfifo_buf: Implement data_available() callback
This patch implements the data_available() callback for the kfifo buffer instead
of using the stufftoread flag. The kfifo used by the buffer already knows
whether it is empty or not based on the position of its read and write pointer.
Using this makes it a lot easier to tell whether data is available or not and it
is not necessary to take special measures to ensure that no race conditions
between reading and writing from the buffer occur.

Note, that we still have to take the buffers lock to protect against concurrent
resizeing of the kfifo.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
2013-12-03 20:22:28 +00:00

193 lines
4.2 KiB
C

#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>
#include <linux/poll.h>
struct iio_kfifo {
struct iio_buffer buffer;
struct kfifo kf;
struct mutex user_lock;
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;
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);
mutex_lock(&buf->user_lock);
if (buf->update_needed) {
kfifo_free(&buf->kf);
ret = __iio_allocate_kfifo(buf, buf->buffer.bytes_per_datum,
buf->buffer.length);
buf->update_needed = false;
} else {
kfifo_reset_out(&buf->kf);
}
mutex_unlock(&buf->user_lock);
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,
const void *data)
{
int ret;
struct iio_kfifo *kf = iio_to_kfifo(r);
ret = kfifo_in(&kf->kf, data, 1);
if (ret != 1)
return -EBUSY;
wake_up_interruptible_poll(&r->pollq, POLLIN | POLLRDNORM);
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 (mutex_lock_interruptible(&kf->user_lock))
return -ERESTARTSYS;
if (!kfifo_initialized(&kf->kf) || n < kfifo_esize(&kf->kf))
ret = -EINVAL;
else
ret = kfifo_to_user(&kf->kf, buf, n, &copied);
mutex_unlock(&kf->user_lock);
if (ret < 0)
return ret;
return copied;
}
static bool iio_kfifo_buf_data_available(struct iio_buffer *r)
{
struct iio_kfifo *kf = iio_to_kfifo(r);
bool empty;
mutex_lock(&kf->user_lock);
empty = kfifo_is_empty(&kf->kf);
mutex_unlock(&kf->user_lock);
return !empty;
}
static void iio_kfifo_buffer_release(struct iio_buffer *buffer)
{
struct iio_kfifo *kf = iio_to_kfifo(buffer);
mutex_destroy(&kf->user_lock);
kfifo_free(&kf->kf);
kfree(kf);
}
static const struct iio_buffer_access_funcs kfifo_access_funcs = {
.store_to = &iio_store_to_kfifo,
.read_first_n = &iio_read_first_n_kfifo,
.data_available = iio_kfifo_buf_data_available,
.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,
.release = &iio_kfifo_buffer_release,
};
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;
mutex_init(&kf->user_lock);
return &kf->buffer;
}
EXPORT_SYMBOL(iio_kfifo_allocate);
void iio_kfifo_free(struct iio_buffer *r)
{
iio_buffer_put(r);
}
EXPORT_SYMBOL(iio_kfifo_free);
MODULE_LICENSE("GPL");