Linux-2.6.33.2/drivers/staging/iio/ring_sw.h
/* 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.
*
* This code is deliberately kept separate from the main industrialio I/O core
* as it is intended that in the future a number of different software ring
* buffer implementations will exist with different characteristics to suit
* different applications.
*
* This particular one was designed for a data capture application where it was
* particularly important that no userspace reads would interrupt the capture
* process. To this end the ring is not locked during a read.
*
* Comments on this buffer design welcomed. It's far from efficient and some of
* my understanding of the effects of scheduling on this are somewhat limited.
* Frankly, to my mind, this is the current weak point in the industrial I/O
* patch set.
*/
#ifndef _IIO_RING_SW_H_
#define _IIO_RING_SW_H_
/* NEEDS COMMENTS */
/* The intention is that this should be a separate module from the iio core.
* This is a bit like supporting algorithms dependent on what the device
* driver requests - some may support multiple options */
#include "iio.h"
#include "ring_generic.h"
#if defined CONFIG_IIO_SW_RING || defined CONFIG_IIO_SW_RING_MODULE
/**
* iio_create_sw_rb() - software ring buffer allocation
* @r: pointer to ring buffer pointer
**/
int iio_create_sw_rb(struct iio_ring_buffer **r);
/**
* iio_init_sw_rb() - initialize the software ring buffer
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
* @indio_dev: industrial I/O device structure
**/
int iio_init_sw_rb(struct iio_ring_buffer *r, struct iio_dev *indio_dev);
/**
* iio_exit_sw_rb() - reverse what was done in iio_init_sw_rb
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
void iio_exit_sw_rb(struct iio_ring_buffer *r);
/**
* iio_free_sw_rb() - free memory occupied by the core ring buffer struct
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
void iio_free_sw_rb(struct iio_ring_buffer *r);
/**
* iio_mark_sw_rb_in_use() - reference counting to prevent incorrect chances
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r);
/**
* iio_unmark_sw_rb_in_use() - notify the ring buffer that we don't care anymore
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r);
/**
* iio_read_last_from_sw_rb() - attempt to read the last stored datum from the rb
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
* @data: where to store the last datum
**/
int iio_read_last_from_sw_rb(struct iio_ring_buffer *r, u8 *data);
/**
* iio_store_to_sw_rb() - store a new datum to the ring buffer
* @r: pointer to ring buffer instance
* @data: the datum to be stored including timestamp if relevant
* @timestamp: timestamp which will be attached to buffer events if relevant
**/
int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp);
/**
* iio_rip_sw_rb() - attempt to read data from the ring buffer
* @r: ring buffer instance
* @count: number of datum's to try and read
* @data: where the data will be stored.
* @dead_offset: how much of the stored data was possibly invalidated by
* the end of the copy.
**/
int iio_rip_sw_rb(struct iio_ring_buffer *r,
size_t count,
u8 **data,
int *dead_offset);
/**
* iio_request_update_sw_rb() - update params if update needed
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
int iio_request_update_sw_rb(struct iio_ring_buffer *r);
/**
* iio_mark_update_needed_sw_rb() - tell the ring buffer it needs a param update
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r);
/**
* iio_get_bpd_sw_rb() - get the datum size in bytes
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
int iio_get_bpd_sw_rb(struct iio_ring_buffer *r);
/**
* iio_set_bpd_sw_rb() - set the datum size in bytes
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
* @bpd: bytes per datum value
**/
int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd);
/**
* iio_get_length_sw_rb() - get how many datums the rb may contain
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
**/
int iio_get_length_sw_rb(struct iio_ring_buffer *r);
/**
* iio_set_length_sw_rb() - set how many datums the rb may contain
* @r: pointer to a software ring buffer created by an
* iio_create_sw_rb call
* @length: max number of data items for the ring buffer
**/
int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length);
/**
* iio_ring_sw_register_funcs() - helper function to set up rb access
* @ra: pointer to @iio_ring_access_funcs
**/
static inline void iio_ring_sw_register_funcs(struct iio_ring_access_funcs *ra)
{
ra->mark_in_use = &iio_mark_sw_rb_in_use;
ra->unmark_in_use = &iio_unmark_sw_rb_in_use;
ra->store_to = &iio_store_to_sw_rb;
ra->read_last = &iio_read_last_from_sw_rb;
ra->rip_lots = &iio_rip_sw_rb;
ra->mark_param_change = &iio_mark_update_needed_sw_rb;
ra->request_update = &iio_request_update_sw_rb;
ra->get_bpd = &iio_get_bpd_sw_rb;
ra->set_bpd = &iio_set_bpd_sw_rb;
ra->get_length = &iio_get_length_sw_rb;
ra->set_length = &iio_set_length_sw_rb;
};
/**
* struct iio_sw_ring_buffer - software ring buffer
* @buf: generic ring buffer elements
* @data: the ring buffer memory
* @read_p: read pointer (oldest available)
* @write_p: write pointer
* @last_written_p: read pointer (newest available)
* @half_p: half buffer length behind write_p (event generation)
* @use_count: reference count to prevent resizing when in use
* @update_needed: flag to indicated change in size requested
* @use_lock: lock to prevent change in size when in use
*
* Note that the first element of all ring buffers must be a
* struct iio_ring_buffer.
**/
struct iio_sw_ring_buffer {
struct iio_ring_buffer buf;
unsigned char *data;
unsigned char *read_p;
unsigned char *write_p;
unsigned char *last_written_p;
/* used to act as a point at which to signal an event */
unsigned char *half_p;
int use_count;
int update_needed;
spinlock_t use_lock;
};
#define iio_to_sw_ring(r) container_of(r, struct iio_sw_ring_buffer, buf)
struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev);
void iio_sw_rb_free(struct iio_ring_buffer *ring);
#else /* CONFIG_IIO_RING_BUFFER*/
static inline void iio_ring_sw_register_funcs(struct iio_ring_access_funcs *ra)
{};
#endif /* !CONFIG_IIO_RING_BUFFER */
#endif /* _IIO_RING_SW_H_ */