[net-next-2.6.git] / drivers / staging / iio / ring_sw.c

/* The industrial I/O simple minimally locked ring buffer.
 *
 * Copyright (c) 2008 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.
 */

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/workqueue.h>
#include "ring_sw.h"

static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
						int bytes_per_datum, int length)
{
	if ((length == 0) || (bytes_per_datum == 0))
		return -EINVAL;
	__iio_update_ring_buffer(&ring->buf, bytes_per_datum, length);
	ring->data = kmalloc(length*ring->buf.bpd, GFP_KERNEL);
	ring->read_p = 0;
	ring->write_p = 0;
	ring->last_written_p = 0;
	ring->half_p = 0;
	return ring->data ? 0 : -ENOMEM;
}

static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
{
	spin_lock_init(&ring->use_lock);
}

static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
{
	kfree(ring->data);
}

void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
{
	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	spin_lock(&ring->use_lock);
	ring->use_count++;
	spin_unlock(&ring->use_lock);
}
EXPORT_SYMBOL(iio_mark_sw_rb_in_use);

void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
{
	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	spin_lock(&ring->use_lock);
	ring->use_count--;
	spin_unlock(&ring->use_lock);
}
EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);


/* Ring buffer related functionality */
/* Store to ring is typically called in the bh of a data ready interrupt handler
 * in the device driver */
/* Lock always held if their is a chance this may be called */
/* Only one of these per ring may run concurrently - enforced by drivers */
int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
			 unsigned char *data,
			 s64 timestamp)
{
	int ret = 0;
	int code;
	unsigned char *temp_ptr, *change_test_ptr;

	/* initial store */
	if (unlikely(ring->write_p == 0)) {
		ring->write_p = ring->data;
		/* Doesn't actually matter if this is out of the set
		 * as long as the read pointer is valid before this
		 * passes it - guaranteed as set later in this function.
		 */
		ring->half_p = ring->data - ring->buf.length*ring->buf.bpd/2;
	}
	/* Copy data to where ever the current write pointer says */
	memcpy(ring->write_p, data, ring->buf.bpd);
	barrier();
	/* Update the pointer used to get most recent value.
	 * Always valid as either points to latest or second latest value.
	 * Before this runs it is null and read attempts fail with -EAGAIN.
	 */
	ring->last_written_p = ring->write_p;
	barrier();
	/* temp_ptr used to ensure we never have an invalid pointer
	 * it may be slightly lagging, but never invalid
	 */
	temp_ptr = ring->write_p + ring->buf.bpd;
	/* End of ring, back to the beginning */
	if (temp_ptr == ring->data + ring->buf.length*ring->buf.bpd)
		temp_ptr = ring->data;
	/* Update the write pointer
	 * always valid as long as this is the only function able to write.
	 * Care needed with smp systems to ensure more than one ring fill
	 * is never scheduled.
	 */
	ring->write_p = temp_ptr;

	if (ring->read_p == 0)
		ring->read_p = ring->data;
	/* Buffer full - move the read pointer and create / escalate
	 * ring event */
	/* Tricky case - if the read pointer moves before we adjust it.
	 * Handle by not pushing if it has moved - may result in occasional
	 * unnecessary buffer full events when it wasn't quite true.
	 */
	else if (ring->write_p == ring->read_p) {
		change_test_ptr = ring->read_p;
		temp_ptr = change_test_ptr + ring->buf.bpd;
		if (temp_ptr
		    == ring->data + ring->buf.length*ring->buf.bpd) {
			temp_ptr = ring->data;
		}
		/* We are moving pointer on one because the ring is full.  Any
		 * change to the read pointer will be this or greater.
		 */
		if (change_test_ptr == ring->read_p)
			ring->read_p = temp_ptr;

		spin_lock(&ring->buf.shared_ev_pointer.lock);

		ret = iio_push_or_escallate_ring_event(&ring->buf,
						       IIO_EVENT_CODE_RING_100_FULL,
						       timestamp);
		spin_unlock(&ring->buf.shared_ev_pointer.lock);
		if (ret)
			goto error_ret;
	}
	/* investigate if our event barrier has been passed */
	/* There are definite 'issues' with this and chances of
	 * simultaneous read */
	/* Also need to use loop count to ensure this only happens once */
	ring->half_p += ring->buf.bpd;
	if (ring->half_p == ring->data + ring->buf.length*ring->buf.bpd)
		ring->half_p = ring->data;
	if (ring->half_p == ring->read_p) {
		spin_lock(&ring->buf.shared_ev_pointer.lock);
		code = IIO_EVENT_CODE_RING_50_FULL;
		ret = __iio_push_event(&ring->buf.ev_int,
				       code,
				       timestamp,
				       &ring->buf.shared_ev_pointer);
		spin_unlock(&ring->buf.shared_ev_pointer.lock);
	}
error_ret:
	return ret;
}

int iio_rip_sw_rb(struct iio_ring_buffer *r,
		  size_t count, u8 **data, int *dead_offset)
{
	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);

	u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
	int ret, max_copied;
	int bytes_to_rip;

	/* A userspace program has probably made an error if it tries to
	 *  read something that is not a whole number of bpds.
	 * Return an error.
	 */
	if (count % ring->buf.bpd) {
		ret = -EINVAL;
		printk(KERN_INFO "Ring buffer read request not whole number of"
		       "samples: Request bytes %zd, Current bpd %d\n",
		       count, ring->buf.bpd);
		goto error_ret;
	}
	/* Limit size to whole of ring buffer */
	bytes_to_rip = min((size_t)(ring->buf.bpd*ring->buf.length), count);

	*data = kmalloc(bytes_to_rip, GFP_KERNEL);
	if (*data == NULL) {
		ret = -ENOMEM;
		goto error_ret;
	}

	/* build local copy */
	initial_read_p = ring->read_p;
	if (unlikely(initial_read_p == 0)) { /* No data here as yet */
		ret = 0;
		goto error_free_data_cpy;
	}

	initial_write_p = ring->write_p;

	/* Need a consistent pair */
	while ((initial_read_p != ring->read_p)
	       || (initial_write_p != ring->write_p)) {
		initial_read_p = ring->read_p;
		initial_write_p = ring->write_p;
	}
	if (initial_write_p == initial_read_p) {
		/* No new data available.*/
		ret = 0;
		goto error_free_data_cpy;
	}

	if (initial_write_p >= initial_read_p + bytes_to_rip) {
		/* write_p is greater than necessary, all is easy */
		max_copied = bytes_to_rip;
		memcpy(*data, initial_read_p, max_copied);
		end_read_p = initial_read_p + max_copied;
	} else if (initial_write_p > initial_read_p) {
		/*not enough data to cpy */
		max_copied = initial_write_p - initial_read_p;
		memcpy(*data, initial_read_p, max_copied);
		end_read_p = initial_write_p;
	} else {
		/* going through 'end' of ring buffer */
		max_copied = ring->data
			+ ring->buf.length*ring->buf.bpd - initial_read_p;
		memcpy(*data, initial_read_p, max_copied);
		/* possible we are done if we align precisely with end */
		if (max_copied == bytes_to_rip)
			end_read_p = ring->data;
		else if (initial_write_p
			 > ring->data + bytes_to_rip - max_copied) {
			/* enough data to finish */
			memcpy(*data + max_copied, ring->data,
			       bytes_to_rip - max_copied);
			max_copied = bytes_to_rip;
			end_read_p = ring->data + (bytes_to_rip - max_copied);
		} else {  /* not enough data */
			memcpy(*data + max_copied, ring->data,
			       initial_write_p - ring->data);
			max_copied += initial_write_p - ring->data;
			end_read_p = initial_write_p;
		}
	}
	/* Now to verify which section was cleanly copied - i.e. how far
	 * read pointer has been pushed */
	current_read_p = ring->read_p;

	if (initial_read_p <= current_read_p)
		*dead_offset = current_read_p - initial_read_p;
	else
		*dead_offset = ring->buf.length*ring->buf.bpd
			- (initial_read_p - current_read_p);

	/* possible issue if the initial write has been lapped or indeed
	 * the point we were reading to has been passed */
	/* No valid data read.
	 * In this case the read pointer is already correct having been
	 * pushed further than we would look. */
	if (max_copied - *dead_offset < 0) {
		ret = 0;
		goto error_free_data_cpy;
	}

	/* setup the next read position */
	/* Beware, this may fail due to concurrency fun and games.
	 *  Possible that sufficient fill commands have run to push the read
	 * pointer past where we would be after the rip. If this occurs, leave
	 * it be.
	 */
	/* Tricky - deal with loops */

	while (ring->read_p != end_read_p)
		ring->read_p = end_read_p;

	return max_copied - *dead_offset;

error_free_data_cpy:
	kfree(*data);
error_ret:
	return ret;
}
EXPORT_SYMBOL(iio_rip_sw_rb);

int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
{
	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	return iio_store_to_sw_ring(ring, data, timestamp);
}
EXPORT_SYMBOL(iio_store_to_sw_rb);

int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
			       unsigned char *data)
{
	unsigned char *last_written_p_copy;

	iio_mark_sw_rb_in_use(&ring->buf);
again:
	barrier();
	last_written_p_copy = ring->last_written_p;
	barrier(); /*unnessecary? */
	/* Check there is anything here */
	if (last_written_p_copy == 0)
		return -EAGAIN;
	memcpy(data, last_written_p_copy, ring->buf.bpd);

	if (unlikely(ring->last_written_p >= last_written_p_copy))
		goto again;

	iio_unmark_sw_rb_in_use(&ring->buf);
	return 0;
}

int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
			     unsigned char *data)
{
	return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
}
EXPORT_SYMBOL(iio_read_last_from_sw_rb);

int iio_request_update_sw_rb(struct iio_ring_buffer *r)
{
	int ret = 0;
	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);

	spin_lock(&ring->use_lock);
	if (!ring->update_needed)
		goto error_ret;
	if (ring->use_count) {
		ret = -EAGAIN;
		goto error_ret;
	}
	__iio_free_sw_ring_buffer(ring);
	ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bpd,
					    ring->buf.length);
error_ret:
	spin_unlock(&ring->use_lock);
	return ret;
}
EXPORT_SYMBOL(iio_request_update_sw_rb);

int iio_get_bpd_sw_rb(struct iio_ring_buffer *r)
{
	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	return ring->buf.bpd;
}
EXPORT_SYMBOL(iio_get_bpd_sw_rb);

int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd)
{
	if (r->bpd != bpd) {
		r->bpd = bpd;
		if (r->access.mark_param_change)
			r->access.mark_param_change(r);
	}
	return 0;
}
EXPORT_SYMBOL(iio_set_bpd_sw_rb);

int iio_get_length_sw_rb(struct iio_ring_buffer *r)
{
	return r->length;
}
EXPORT_SYMBOL(iio_get_length_sw_rb);

int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
{
	if (r->length != length) {
		r->length = length;
		if (r->access.mark_param_change)
			r->access.mark_param_change(r);
	}
	return 0;
}
EXPORT_SYMBOL(iio_set_length_sw_rb);

int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
{
	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	ring->update_needed = true;
	return 0;
}
EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);

static void iio_sw_rb_release(struct device *dev)
{
	struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
	kfree(iio_to_sw_ring(r));
}

static IIO_RING_ENABLE_ATTR;
static IIO_RING_BPS_ATTR;
static IIO_RING_LENGTH_ATTR;

/* Standard set of ring buffer attributes */
static struct attribute *iio_ring_attributes[] = {
	&dev_attr_length.attr,
	&dev_attr_bps.attr,
	&dev_attr_ring_enable.attr,
	NULL,
};

static struct attribute_group iio_ring_attribute_group = {
	.attrs = iio_ring_attributes,
};

static const struct attribute_group *iio_ring_attribute_groups[] = {
	&iio_ring_attribute_group,
	NULL
};

static struct device_type iio_sw_ring_type = {
	.release = iio_sw_rb_release,
	.groups = iio_ring_attribute_groups,
};

struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
{
	struct iio_ring_buffer *buf;
	struct iio_sw_ring_buffer *ring;

	ring = kzalloc(sizeof *ring, GFP_KERNEL);
	if (!ring)
		return 0;
	buf = &ring->buf;
	iio_ring_buffer_init(buf, indio_dev);
	__iio_init_sw_ring_buffer(ring);
	buf->dev.type = &iio_sw_ring_type;
	device_initialize(&buf->dev);
	buf->dev.parent = &indio_dev->dev;
	buf->dev.class = &iio_class;
	dev_set_drvdata(&buf->dev, (void *)buf);

	return buf;
}
EXPORT_SYMBOL(iio_sw_rb_allocate);

void iio_sw_rb_free(struct iio_ring_buffer *r)
{
	if (r)
		iio_put_ring_buffer(r);
}
EXPORT_SYMBOL(iio_sw_rb_free);
MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
MODULE_LICENSE("GPL");
Commit	Line	Data
2235acb2 JC	1	/* The industrial I/O simple minimally locked ring buffer.
	2	*
	3	* Copyright (c) 2008 Jonathan Cameron
	4	*
	5	* This program is free software; you can redistribute it and/or modify it
	6	* under the terms of the GNU General Public License version 2 as published by
	7	* the Free Software Foundation.
	8	*/
	9
5a0e3ad6	10	#include <linux/slab.h>
2235acb2	11	#include <linux/kernel.h>
2235acb2 JC	12	#include <linux/module.h>
	13	#include <linux/device.h>
	14	#include <linux/workqueue.h>
	15	#include "ring_sw.h"
	16
6f2dfb31 JC	17	static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
6f2dfb31 JC	18	int bytes_per_datum, int length)
2235acb2 JC	19	{
	20	if ((length == 0) \|\| (bytes_per_datum == 0))
	21	return -EINVAL;
6f2dfb31	22	__iio_update_ring_buffer(&ring->buf, bytes_per_datum, length);
2235acb2 JC	23	ring->data = kmalloc(length*ring->buf.bpd, GFP_KERNEL);
	24	ring->read_p = 0;
	25	ring->write_p = 0;
	26	ring->last_written_p = 0;
	27	ring->half_p = 0;
	28	return ring->data ? 0 : -ENOMEM;
	29	}
	30
6f2dfb31 JC	31	static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
	32	{
	33	spin_lock_init(&ring->use_lock);
	34	}
	35
2235acb2 JC	36	static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
	37	{
	38	kfree(ring->data);
	39	}
	40
	41	void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
	42	{
	43	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	44	spin_lock(&ring->use_lock);
	45	ring->use_count++;
	46	spin_unlock(&ring->use_lock);
	47	}
	48	EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
	49
	50	void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
	51	{
	52	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	53	spin_lock(&ring->use_lock);
	54	ring->use_count--;
	55	spin_unlock(&ring->use_lock);
	56	}
	57	EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
	58
	59
	60	/* Ring buffer related functionality */
	61	/* Store to ring is typically called in the bh of a data ready interrupt handler
	62	* in the device driver */
	63	/* Lock always held if their is a chance this may be called */
	64	/* Only one of these per ring may run concurrently - enforced by drivers */
	65	int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
	66	unsigned char *data,
	67	s64 timestamp)
	68	{
	69	int ret = 0;
	70	int code;
	71	unsigned char temp_ptr, change_test_ptr;
	72
	73	/* initial store */
	74	if (unlikely(ring->write_p == 0)) {
	75	ring->write_p = ring->data;
	76	/* Doesn't actually matter if this is out of the set
	77	* as long as the read pointer is valid before this
	78	* passes it - guaranteed as set later in this function.
	79	*/
	80	ring->half_p = ring->data - ring->buf.length*ring->buf.bpd/2;
	81	}
	82	/* Copy data to where ever the current write pointer says */
	83	memcpy(ring->write_p, data, ring->buf.bpd);
	84	barrier();
	85	/* Update the pointer used to get most recent value.
	86	* Always valid as either points to latest or second latest value.
	87	* Before this runs it is null and read attempts fail with -EAGAIN.
	88	*/
	89	ring->last_written_p = ring->write_p;
	90	barrier();
	91	/* temp_ptr used to ensure we never have an invalid pointer
	92	* it may be slightly lagging, but never invalid
	93	*/
	94	temp_ptr = ring->write_p + ring->buf.bpd;
	95	/* End of ring, back to the beginning */
	96	if (temp_ptr == ring->data + ring->buf.length*ring->buf.bpd)
	97	temp_ptr = ring->data;
	98	/* Update the write pointer
	99	* always valid as long as this is the only function able to write.
100	* Care needed with smp systems to ensure more than one ring fill
101	* is never scheduled.
102	*/
103	ring->write_p = temp_ptr;
104
105	if (ring->read_p == 0)
106	ring->read_p = ring->data;
107	/* Buffer full - move the read pointer and create / escalate
108	* ring event */
109	/* Tricky case - if the read pointer moves before we adjust it.
110	* Handle by not pushing if it has moved - may result in occasional
111	* unnecessary buffer full events when it wasn't quite true.
112	*/
113	else if (ring->write_p == ring->read_p) {
114	change_test_ptr = ring->read_p;
115	temp_ptr = change_test_ptr + ring->buf.bpd;
116	if (temp_ptr
117	== ring->data + ring->buf.length*ring->buf.bpd) {
118	temp_ptr = ring->data;
119	}
120	/* We are moving pointer on one because the ring is full. Any
121	* change to the read pointer will be this or greater.
122	*/
123	if (change_test_ptr == ring->read_p)
124	ring->read_p = temp_ptr;
125
126	spin_lock(&ring->buf.shared_ev_pointer.lock);
127
128	ret = iio_push_or_escallate_ring_event(&ring->buf,
129	IIO_EVENT_CODE_RING_100_FULL,
130	timestamp);
131	spin_unlock(&ring->buf.shared_ev_pointer.lock);
132	if (ret)
133	goto error_ret;
134	}
135	/* investigate if our event barrier has been passed */
136	/* There are definite 'issues' with this and chances of
137	* simultaneous read */
138	/* Also need to use loop count to ensure this only happens once */
139	ring->half_p += ring->buf.bpd;
140	if (ring->half_p == ring->data + ring->buf.length*ring->buf.bpd)
141	ring->half_p = ring->data;
142	if (ring->half_p == ring->read_p) {
143	spin_lock(&ring->buf.shared_ev_pointer.lock);
144	code = IIO_EVENT_CODE_RING_50_FULL;
145	ret = __iio_push_event(&ring->buf.ev_int,
146	code,
147	timestamp,
148	&ring->buf.shared_ev_pointer);
149	spin_unlock(&ring->buf.shared_ev_pointer.lock);
150	}
151	error_ret:
152	return ret;
153	}
154
155	int iio_rip_sw_rb(struct iio_ring_buffer *r,
156	size_t count, u8 *data, int dead_offset)
157	{
158	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
159
160	u8 initial_read_p, initial_write_p, current_read_p, end_read_p;
161	int ret, max_copied;
162	int bytes_to_rip;
163
164	/* A userspace program has probably made an error if it tries to
165	* read something that is not a whole number of bpds.
166	* Return an error.
167	*/
168	if (count % ring->buf.bpd) {
169	ret = -EINVAL;
170	printk(KERN_INFO "Ring buffer read request not whole number of"
171	"samples: Request bytes %zd, Current bpd %d\n",
172	count, ring->buf.bpd);
173	goto error_ret;
174	}
175	/* Limit size to whole of ring buffer */
176	bytes_to_rip = min((size_t)(ring->buf.bpd*ring->buf.length), count);
177
178	*data = kmalloc(bytes_to_rip, GFP_KERNEL);
179	if (*data == NULL) {
180	ret = -ENOMEM;
181	goto error_ret;
182	}
183
184	/* build local copy */
185	initial_read_p = ring->read_p;
186	if (unlikely(initial_read_p == 0)) { /* No data here as yet */
187	ret = 0;
188	goto error_free_data_cpy;
189	}
190
191	initial_write_p = ring->write_p;
192
193	/* Need a consistent pair */
194	while ((initial_read_p != ring->read_p)
195	\|\| (initial_write_p != ring->write_p)) {
196	initial_read_p = ring->read_p;
197	initial_write_p = ring->write_p;
198	}
199	if (initial_write_p == initial_read_p) {
200	/* No new data available.*/
201	ret = 0;
202	goto error_free_data_cpy;
203	}
204
205	if (initial_write_p >= initial_read_p + bytes_to_rip) {
206	/* write_p is greater than necessary, all is easy */
207	max_copied = bytes_to_rip;
208	memcpy(*data, initial_read_p, max_copied);
209	end_read_p = initial_read_p + max_copied;
210	} else if (initial_write_p > initial_read_p) {
211	/not enough data to cpy /
212	max_copied = initial_write_p - initial_read_p;
213	memcpy(*data, initial_read_p, max_copied);
214	end_read_p = initial_write_p;
215	} else {
216	/* going through 'end' of ring buffer */
217	max_copied = ring->data
218	+ ring->buf.length*ring->buf.bpd - initial_read_p;
219	memcpy(*data, initial_read_p, max_copied);
220	/* possible we are done if we align precisely with end */
221	if (max_copied == bytes_to_rip)
222	end_read_p = ring->data;
223	else if (initial_write_p
224	> ring->data + bytes_to_rip - max_copied) {
225	/* enough data to finish */
226	memcpy(*data + max_copied, ring->data,
227	bytes_to_rip - max_copied);
228	max_copied = bytes_to_rip;
229	end_read_p = ring->data + (bytes_to_rip - max_copied);
230	} else { /* not enough data */
231	memcpy(*data + max_copied, ring->data,
232	initial_write_p - ring->data);
233	max_copied += initial_write_p - ring->data;
234	end_read_p = initial_write_p;
235	}
236	}
237	/* Now to verify which section was cleanly copied - i.e. how far
238	* read pointer has been pushed */
239	current_read_p = ring->read_p;
240
241	if (initial_read_p <= current_read_p)
242	*dead_offset = current_read_p - initial_read_p;
243	else
244	dead_offset = ring->buf.lengthring->buf.bpd
245	- (initial_read_p - current_read_p);
246
247	/* possible issue if the initial write has been lapped or indeed
248	* the point we were reading to has been passed */
249	/* No valid data read.
250	* In this case the read pointer is already correct having been
251	* pushed further than we would look. */
252	if (max_copied - *dead_offset < 0) {
253	ret = 0;
254	goto error_free_data_cpy;
255	}
256
257	/* setup the next read position */
258	/* Beware, this may fail due to concurrency fun and games.
259	* Possible that sufficient fill commands have run to push the read
260	* pointer past where we would be after the rip. If this occurs, leave
261	* it be.
262	*/
263	/* Tricky - deal with loops */
264
265	while (ring->read_p != end_read_p)
266	ring->read_p = end_read_p;
267
268	return max_copied - *dead_offset;
269
270	error_free_data_cpy:
271	kfree(*data);
272	error_ret:
273	return ret;
274	}
275	EXPORT_SYMBOL(iio_rip_sw_rb);
276
277	int iio_store_to_sw_rb(struct iio_ring_buffer r, u8 data, s64 timestamp)
278	{
279	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
280	return iio_store_to_sw_ring(ring, data, timestamp);
281	}
282	EXPORT_SYMBOL(iio_store_to_sw_rb);
283
284	int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
285	unsigned char *data)
286	{
287	unsigned char *last_written_p_copy;
288
289	iio_mark_sw_rb_in_use(&ring->buf);
290	again:
291	barrier();
292	last_written_p_copy = ring->last_written_p;
293	barrier(); /unnessecary? /
294	/* Check there is anything here */
295	if (last_written_p_copy == 0)
296	return -EAGAIN;
297	memcpy(data, last_written_p_copy, ring->buf.bpd);
298
299	if (unlikely(ring->last_written_p >= last_written_p_copy))
300	goto again;
301
302	iio_unmark_sw_rb_in_use(&ring->buf);
303	return 0;
304	}
305
306	int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
307	unsigned char *data)
308	{
309	return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
310	}
311	EXPORT_SYMBOL(iio_read_last_from_sw_rb);
312
313	int iio_request_update_sw_rb(struct iio_ring_buffer *r)
314	{
315	int ret = 0;
316	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
317
318	spin_lock(&ring->use_lock);
319	if (!ring->update_needed)
320	goto error_ret;
321	if (ring->use_count) {
322	ret = -EAGAIN;
323	goto error_ret;
324	}
325	__iio_free_sw_ring_buffer(ring);
6f2dfb31 JC	326	ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bpd,
6f2dfb31 JC	327	ring->buf.length);
2235acb2 JC	328	error_ret:
	329	spin_unlock(&ring->use_lock);
	330	return ret;
	331	}
	332	EXPORT_SYMBOL(iio_request_update_sw_rb);
	333
	334	int iio_get_bpd_sw_rb(struct iio_ring_buffer *r)
	335	{
	336	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	337	return ring->buf.bpd;
	338	}
	339	EXPORT_SYMBOL(iio_get_bpd_sw_rb);
	340
	341	int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd)
	342	{
	343	if (r->bpd != bpd) {
	344	r->bpd = bpd;
	345	if (r->access.mark_param_change)
	346	r->access.mark_param_change(r);
	347	}
	348	return 0;
	349	}
	350	EXPORT_SYMBOL(iio_set_bpd_sw_rb);
	351
	352	int iio_get_length_sw_rb(struct iio_ring_buffer *r)
	353	{
	354	return r->length;
	355	}
	356	EXPORT_SYMBOL(iio_get_length_sw_rb);
	357
	358	int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
	359	{
	360	if (r->length != length) {
	361	r->length = length;
	362	if (r->access.mark_param_change)
	363	r->access.mark_param_change(r);
	364	}
	365	return 0;
	366	}
	367	EXPORT_SYMBOL(iio_set_length_sw_rb);
	368
	369	int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
	370	{
	371	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
	372	ring->update_needed = true;
	373	return 0;
	374	}
	375	EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
	376
	377	static void iio_sw_rb_release(struct device *dev)
	378	{
	379	struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
	380	kfree(iio_to_sw_ring(r));
	381	}
	382
	383	static IIO_RING_ENABLE_ATTR;
	384	static IIO_RING_BPS_ATTR;
	385	static IIO_RING_LENGTH_ATTR;
	386
	387	/* Standard set of ring buffer attributes */
	388	static struct attribute *iio_ring_attributes[] = {
	389	&dev_attr_length.attr,
	390	&dev_attr_bps.attr,
	391	&dev_attr_ring_enable.attr,
392	NULL,
393	};
394
395	static struct attribute_group iio_ring_attribute_group = {
396	.attrs = iio_ring_attributes,
397	};
398
3860dc82	399	static const struct attribute_group *iio_ring_attribute_groups[] = {
2235acb2 JC	400	&iio_ring_attribute_group,
	401	NULL
	402	};
	403
	404	static struct device_type iio_sw_ring_type = {
	405	.release = iio_sw_rb_release,
	406	.groups = iio_ring_attribute_groups,
	407	};
	408
	409	struct iio_ring_buffer iio_sw_rb_allocate(struct iio_dev indio_dev)
	410	{
	411	struct iio_ring_buffer *buf;
	412	struct iio_sw_ring_buffer *ring;
	413
	414	ring = kzalloc(sizeof *ring, GFP_KERNEL);
	415	if (!ring)
	416	return 0;
	417	buf = &ring->buf;
2235acb2	418	iio_ring_buffer_init(buf, indio_dev);
6f2dfb31	419	__iio_init_sw_ring_buffer(ring);
2235acb2 JC	420	buf->dev.type = &iio_sw_ring_type;
	421	device_initialize(&buf->dev);
	422	buf->dev.parent = &indio_dev->dev;
	423	buf->dev.class = &iio_class;
	424	dev_set_drvdata(&buf->dev, (void *)buf);
	425
	426	return buf;
	427	}
	428	EXPORT_SYMBOL(iio_sw_rb_allocate);
	429
	430	void iio_sw_rb_free(struct iio_ring_buffer *r)
	431	{
	432	if (r)
	433	iio_put_ring_buffer(r);
	434	}
	435	EXPORT_SYMBOL(iio_sw_rb_free);
	436	MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
	437	MODULE_LICENSE("GPL");