433 lines
12 KiB
C
433 lines
12 KiB
C
/* The industrial I/O simple minimally locked ring buffer.
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*
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* Copyright (c) 2008 Jonathan Cameron
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/workqueue.h>
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#include "ring_sw.h"
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static inline int __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
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int bytes_per_datum, int length)
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{
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if ((length == 0) || (bytes_per_datum == 0))
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return -EINVAL;
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__iio_init_ring_buffer(&ring->buf, bytes_per_datum, length);
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ring->use_lock = __SPIN_LOCK_UNLOCKED((ring)->use_lock);
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ring->data = kmalloc(length*ring->buf.bpd, GFP_KERNEL);
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ring->read_p = 0;
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ring->write_p = 0;
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ring->last_written_p = 0;
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ring->half_p = 0;
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return ring->data ? 0 : -ENOMEM;
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}
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static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
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{
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kfree(ring->data);
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}
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void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
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{
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struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
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spin_lock(&ring->use_lock);
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ring->use_count++;
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spin_unlock(&ring->use_lock);
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}
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EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
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void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
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{
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struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
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spin_lock(&ring->use_lock);
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ring->use_count--;
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spin_unlock(&ring->use_lock);
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}
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EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
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/* Ring buffer related functionality */
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/* Store to ring is typically called in the bh of a data ready interrupt handler
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* in the device driver */
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/* Lock always held if their is a chance this may be called */
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/* Only one of these per ring may run concurrently - enforced by drivers */
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int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
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unsigned char *data,
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s64 timestamp)
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{
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int ret = 0;
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int code;
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unsigned char *temp_ptr, *change_test_ptr;
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/* initial store */
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if (unlikely(ring->write_p == 0)) {
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ring->write_p = ring->data;
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/* Doesn't actually matter if this is out of the set
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* as long as the read pointer is valid before this
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* passes it - guaranteed as set later in this function.
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*/
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ring->half_p = ring->data - ring->buf.length*ring->buf.bpd/2;
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}
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/* Copy data to where ever the current write pointer says */
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memcpy(ring->write_p, data, ring->buf.bpd);
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barrier();
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/* Update the pointer used to get most recent value.
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* Always valid as either points to latest or second latest value.
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* Before this runs it is null and read attempts fail with -EAGAIN.
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*/
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ring->last_written_p = ring->write_p;
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barrier();
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/* temp_ptr used to ensure we never have an invalid pointer
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* it may be slightly lagging, but never invalid
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*/
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temp_ptr = ring->write_p + ring->buf.bpd;
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/* End of ring, back to the beginning */
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if (temp_ptr == ring->data + ring->buf.length*ring->buf.bpd)
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temp_ptr = ring->data;
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/* Update the write pointer
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* always valid as long as this is the only function able to write.
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* Care needed with smp systems to ensure more than one ring fill
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* is never scheduled.
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*/
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ring->write_p = temp_ptr;
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if (ring->read_p == 0)
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ring->read_p = ring->data;
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/* Buffer full - move the read pointer and create / escalate
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* ring event */
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/* Tricky case - if the read pointer moves before we adjust it.
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* Handle by not pushing if it has moved - may result in occasional
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* unnecessary buffer full events when it wasn't quite true.
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*/
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else if (ring->write_p == ring->read_p) {
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change_test_ptr = ring->read_p;
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temp_ptr = change_test_ptr + ring->buf.bpd;
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if (temp_ptr
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== ring->data + ring->buf.length*ring->buf.bpd) {
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temp_ptr = ring->data;
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}
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/* We are moving pointer on one because the ring is full. Any
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* change to the read pointer will be this or greater.
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*/
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if (change_test_ptr == ring->read_p)
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ring->read_p = temp_ptr;
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spin_lock(&ring->buf.shared_ev_pointer.lock);
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ret = iio_push_or_escallate_ring_event(&ring->buf,
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IIO_EVENT_CODE_RING_100_FULL,
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timestamp);
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spin_unlock(&ring->buf.shared_ev_pointer.lock);
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if (ret)
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goto error_ret;
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}
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/* investigate if our event barrier has been passed */
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/* There are definite 'issues' with this and chances of
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* simultaneous read */
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/* Also need to use loop count to ensure this only happens once */
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ring->half_p += ring->buf.bpd;
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if (ring->half_p == ring->data + ring->buf.length*ring->buf.bpd)
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ring->half_p = ring->data;
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if (ring->half_p == ring->read_p) {
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spin_lock(&ring->buf.shared_ev_pointer.lock);
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code = IIO_EVENT_CODE_RING_50_FULL;
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ret = __iio_push_event(&ring->buf.ev_int,
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code,
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timestamp,
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&ring->buf.shared_ev_pointer);
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spin_unlock(&ring->buf.shared_ev_pointer.lock);
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}
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error_ret:
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return ret;
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}
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int iio_rip_sw_rb(struct iio_ring_buffer *r,
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size_t count, u8 **data, int *dead_offset)
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{
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struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
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u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
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int ret, max_copied;
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int bytes_to_rip;
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/* A userspace program has probably made an error if it tries to
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* read something that is not a whole number of bpds.
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* Return an error.
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*/
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if (count % ring->buf.bpd) {
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ret = -EINVAL;
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printk(KERN_INFO "Ring buffer read request not whole number of"
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"samples: Request bytes %zd, Current bpd %d\n",
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count, ring->buf.bpd);
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goto error_ret;
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}
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/* Limit size to whole of ring buffer */
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bytes_to_rip = min((size_t)(ring->buf.bpd*ring->buf.length), count);
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*data = kmalloc(bytes_to_rip, GFP_KERNEL);
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if (*data == NULL) {
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ret = -ENOMEM;
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goto error_ret;
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}
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/* build local copy */
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initial_read_p = ring->read_p;
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if (unlikely(initial_read_p == 0)) { /* No data here as yet */
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ret = 0;
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goto error_free_data_cpy;
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}
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initial_write_p = ring->write_p;
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/* Need a consistent pair */
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while ((initial_read_p != ring->read_p)
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|| (initial_write_p != ring->write_p)) {
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initial_read_p = ring->read_p;
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initial_write_p = ring->write_p;
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}
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if (initial_write_p == initial_read_p) {
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/* No new data available.*/
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ret = 0;
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goto error_free_data_cpy;
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}
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if (initial_write_p >= initial_read_p + bytes_to_rip) {
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/* write_p is greater than necessary, all is easy */
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max_copied = bytes_to_rip;
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memcpy(*data, initial_read_p, max_copied);
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end_read_p = initial_read_p + max_copied;
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} else if (initial_write_p > initial_read_p) {
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/*not enough data to cpy */
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max_copied = initial_write_p - initial_read_p;
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memcpy(*data, initial_read_p, max_copied);
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end_read_p = initial_write_p;
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} else {
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/* going through 'end' of ring buffer */
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max_copied = ring->data
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+ ring->buf.length*ring->buf.bpd - initial_read_p;
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memcpy(*data, initial_read_p, max_copied);
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/* possible we are done if we align precisely with end */
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if (max_copied == bytes_to_rip)
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end_read_p = ring->data;
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else if (initial_write_p
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> ring->data + bytes_to_rip - max_copied) {
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/* enough data to finish */
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memcpy(*data + max_copied, ring->data,
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bytes_to_rip - max_copied);
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max_copied = bytes_to_rip;
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end_read_p = ring->data + (bytes_to_rip - max_copied);
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} else { /* not enough data */
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memcpy(*data + max_copied, ring->data,
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initial_write_p - ring->data);
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max_copied += initial_write_p - ring->data;
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end_read_p = initial_write_p;
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}
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}
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/* Now to verify which section was cleanly copied - i.e. how far
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* read pointer has been pushed */
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current_read_p = ring->read_p;
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if (initial_read_p <= current_read_p)
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*dead_offset = current_read_p - initial_read_p;
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else
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*dead_offset = ring->buf.length*ring->buf.bpd
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- (initial_read_p - current_read_p);
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/* possible issue if the initial write has been lapped or indeed
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* the point we were reading to has been passed */
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/* No valid data read.
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* In this case the read pointer is already correct having been
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* pushed further than we would look. */
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if (max_copied - *dead_offset < 0) {
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ret = 0;
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goto error_free_data_cpy;
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}
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/* setup the next read position */
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/* Beware, this may fail due to concurrency fun and games.
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* Possible that sufficient fill commands have run to push the read
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* pointer past where we would be after the rip. If this occurs, leave
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* it be.
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*/
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/* Tricky - deal with loops */
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while (ring->read_p != end_read_p)
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ring->read_p = end_read_p;
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return max_copied - *dead_offset;
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error_free_data_cpy:
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kfree(*data);
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error_ret:
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return ret;
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}
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EXPORT_SYMBOL(iio_rip_sw_rb);
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int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
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{
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struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
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return iio_store_to_sw_ring(ring, data, timestamp);
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}
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EXPORT_SYMBOL(iio_store_to_sw_rb);
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int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
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unsigned char *data)
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{
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unsigned char *last_written_p_copy;
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iio_mark_sw_rb_in_use(&ring->buf);
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again:
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barrier();
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last_written_p_copy = ring->last_written_p;
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barrier(); /*unnessecary? */
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/* Check there is anything here */
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if (last_written_p_copy == 0)
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return -EAGAIN;
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memcpy(data, last_written_p_copy, ring->buf.bpd);
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if (unlikely(ring->last_written_p >= last_written_p_copy))
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goto again;
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iio_unmark_sw_rb_in_use(&ring->buf);
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return 0;
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}
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int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
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unsigned char *data)
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{
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return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
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}
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EXPORT_SYMBOL(iio_read_last_from_sw_rb);
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int iio_request_update_sw_rb(struct iio_ring_buffer *r)
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{
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int ret = 0;
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struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
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spin_lock(&ring->use_lock);
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if (!ring->update_needed)
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goto error_ret;
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if (ring->use_count) {
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ret = -EAGAIN;
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goto error_ret;
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}
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__iio_free_sw_ring_buffer(ring);
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ret = __iio_init_sw_ring_buffer(ring, ring->buf.bpd, ring->buf.length);
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error_ret:
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spin_unlock(&ring->use_lock);
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return ret;
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}
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EXPORT_SYMBOL(iio_request_update_sw_rb);
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int iio_get_bpd_sw_rb(struct iio_ring_buffer *r)
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{
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struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
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return ring->buf.bpd;
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}
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EXPORT_SYMBOL(iio_get_bpd_sw_rb);
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int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd)
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{
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if (r->bpd != bpd) {
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r->bpd = bpd;
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if (r->access.mark_param_change)
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r->access.mark_param_change(r);
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}
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return 0;
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}
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EXPORT_SYMBOL(iio_set_bpd_sw_rb);
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int iio_get_length_sw_rb(struct iio_ring_buffer *r)
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{
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return r->length;
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}
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EXPORT_SYMBOL(iio_get_length_sw_rb);
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int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
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{
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if (r->length != length) {
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r->length = length;
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if (r->access.mark_param_change)
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r->access.mark_param_change(r);
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}
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return 0;
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}
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EXPORT_SYMBOL(iio_set_length_sw_rb);
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int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
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{
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struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
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ring->update_needed = true;
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return 0;
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}
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EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
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static void iio_sw_rb_release(struct device *dev)
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{
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struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
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kfree(iio_to_sw_ring(r));
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}
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static IIO_RING_ENABLE_ATTR;
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static IIO_RING_BPS_ATTR;
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static IIO_RING_LENGTH_ATTR;
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/* Standard set of ring buffer attributes */
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static struct attribute *iio_ring_attributes[] = {
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&dev_attr_length.attr,
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&dev_attr_bps.attr,
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&dev_attr_ring_enable.attr,
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NULL,
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};
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static struct attribute_group iio_ring_attribute_group = {
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.attrs = iio_ring_attributes,
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};
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static const struct attribute_group *iio_ring_attribute_groups[] = {
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&iio_ring_attribute_group,
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NULL
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};
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static struct device_type iio_sw_ring_type = {
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.release = iio_sw_rb_release,
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.groups = iio_ring_attribute_groups,
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};
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struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
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{
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struct iio_ring_buffer *buf;
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struct iio_sw_ring_buffer *ring;
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ring = kzalloc(sizeof *ring, GFP_KERNEL);
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if (!ring)
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return 0;
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buf = &ring->buf;
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iio_ring_buffer_init(buf, indio_dev);
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buf->dev.type = &iio_sw_ring_type;
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device_initialize(&buf->dev);
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buf->dev.parent = &indio_dev->dev;
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buf->dev.class = &iio_class;
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dev_set_drvdata(&buf->dev, (void *)buf);
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return buf;
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}
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EXPORT_SYMBOL(iio_sw_rb_allocate);
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void iio_sw_rb_free(struct iio_ring_buffer *r)
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{
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if (r)
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iio_put_ring_buffer(r);
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}
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EXPORT_SYMBOL(iio_sw_rb_free);
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MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
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MODULE_LICENSE("GPL");
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