release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/staging/iio/ring_sw.h

   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  * This code is deliberately kept separate from the main industrialio I/O core
  10  * as it is intended that in the future a number of different software ring
  11  * buffer implementations will exist with different characteristics to suit
  12  * different applications.
  13  *
  14  * This particular one was designed for a data capture application where it was
  15  * particularly important that no userspace reads would interrupt the capture
  16  * process. To this end the ring is not locked during a read.
  17  *
  18  * Comments on this buffer design welcomed. It's far from efficient and some of
  19  * my understanding of the effects of scheduling on this are somewhat limited.
  20  * Frankly, to my mind, this is the current weak point in the industrial I/O
  21  * patch set.
  22  */
  23
  24 #ifndef _IIO_RING_SW_H_
  25 #define _IIO_RING_SW_H_
  26 /* NEEDS COMMENTS */
  27 /* The intention is that this should be a separate module from the iio core.
  28  * This is a bit like supporting algorithms dependent on what the device
  29  * driver requests - some may support multiple options */
  30
  31
  32 #include "iio.h"
  33 #include "ring_generic.h"
  34
  35 #if defined CONFIG_IIO_SW_RING || defined CONFIG_IIO_SW_RING_MODULE
  36
  37 /**
  38  * iio_create_sw_rb() - software ring buffer allocation
  39  * @r:          pointer to ring buffer pointer
  40  **/
  41 int iio_create_sw_rb(struct iio_ring_buffer **r);
  42
  43 /**
  44  * iio_init_sw_rb() - initialize the software ring buffer
  45  * @r:          pointer to a software ring buffer created by an
  46  *              iio_create_sw_rb call
  47  * @indio_dev:          industrial I/O device structure
  48  **/
  49 int iio_init_sw_rb(struct iio_ring_buffer *r, struct iio_dev *indio_dev);
  50
  51 /**
  52  * iio_exit_sw_rb() - reverse what was done in iio_init_sw_rb
  53  * @r:          pointer to a software ring buffer created by an
  54  *              iio_create_sw_rb call
  55  **/
  56 void iio_exit_sw_rb(struct iio_ring_buffer *r);
  57
  58 /**
  59  * iio_free_sw_rb() - free memory occupied by the core ring buffer struct
  60  * @r:          pointer to a software ring buffer created by an
  61  *              iio_create_sw_rb call
  62  **/
  63 void iio_free_sw_rb(struct iio_ring_buffer *r);
  64
  65 /**
  66  * iio_mark_sw_rb_in_use() - reference counting to prevent incorrect chances
  67  * @r:          pointer to a software ring buffer created by an
  68  *              iio_create_sw_rb call
  69  **/
  70 void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r);
  71
  72 /**
  73  *  iio_unmark_sw_rb_in_use() - notify the ring buffer that we don't care anymore
  74  * @r:          pointer to a software ring buffer created by an
  75  *              iio_create_sw_rb call
  76  **/
  77 void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r);
  78
  79 /**
  80  * iio_read_last_from_sw_rb() - attempt to read the last stored datum from the rb
  81  * @r:          pointer to a software ring buffer created by an
  82  *              iio_create_sw_rb call
  83  * @data:       where to store the last datum
  84  **/
  85 int iio_read_last_from_sw_rb(struct iio_ring_buffer *r, u8 *data);
  86
  87 /**
  88  * iio_store_to_sw_rb() - store a new datum to the ring buffer
  89  * @r:          pointer to ring buffer instance
  90  * @data:       the datum to be stored including timestamp if relevant
  91  * @timestamp:  timestamp which will be attached to buffer events if relevant
  92  **/
  93 int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp);
  94
  95 /**
  96  * iio_rip_sw_rb() - attempt to read data from the ring buffer
  97  * @r:                  ring buffer instance
  98  * @count:              number of datum's to try and read
  99  * @data:               where the data will be stored.
 100  * @dead_offset:        how much of the stored data was possibly invalidated by
 101  *                      the end of the copy.
 102  **/
 103 int iio_rip_sw_rb(struct iio_ring_buffer *r,
 104                   size_t count,
 105                   u8 **data,
 106                   int *dead_offset);
 107
 108 /**
 109  * iio_request_update_sw_rb() - update params if update needed
 110  * @r:          pointer to a software ring buffer created by an
 111  *              iio_create_sw_rb call
 112  **/
 113 int iio_request_update_sw_rb(struct iio_ring_buffer *r);
 114
 115 /**
 116  * iio_mark_update_needed_sw_rb() - tell the ring buffer it needs a param update
 117  * @r:          pointer to a software ring buffer created by an
 118  *              iio_create_sw_rb call
 119  **/
 120 int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r);
 121
 122
 123 /**
 124  * iio_get_bpd_sw_rb() - get the datum size in bytes
 125  * @r:          pointer to a software ring buffer created by an
 126  *              iio_create_sw_rb call
 127  **/
 128 int iio_get_bpd_sw_rb(struct iio_ring_buffer *r);
 129
 130 /**
 131  * iio_set_bpd_sw_rb() - set the datum size in bytes
 132  * @r:          pointer to a software ring buffer created by an
 133  *              iio_create_sw_rb call
 134  * @bpd:        bytes per datum value
 135  **/
 136 int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd);
 137
 138 /**
 139  * iio_get_length_sw_rb() - get how many datums the rb may contain
 140  * @r:          pointer to a software ring buffer created by an
 141  *              iio_create_sw_rb call
 142  **/
 143 int iio_get_length_sw_rb(struct iio_ring_buffer *r);
 144
 145 /**
 146  * iio_set_length_sw_rb() - set how many datums the rb may contain
 147  * @r:          pointer to a software ring buffer created by an
 148  *              iio_create_sw_rb call
 149  * @length:     max number of data items for the ring buffer
 150  **/
 151 int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length);
 152
 153 /**
 154  * iio_ring_sw_register_funcs() - helper function to set up rb access
 155  * @ra:         pointer to @iio_ring_access_funcs
 156  **/
 157 static inline void iio_ring_sw_register_funcs(struct iio_ring_access_funcs *ra)
 158 {
 159         ra->mark_in_use = &iio_mark_sw_rb_in_use;
 160         ra->unmark_in_use = &iio_unmark_sw_rb_in_use;
 161
 162         ra->store_to = &iio_store_to_sw_rb;
 163         ra->read_last = &iio_read_last_from_sw_rb;
 164         ra->rip_lots = &iio_rip_sw_rb;
 165
 166         ra->mark_param_change = &iio_mark_update_needed_sw_rb;
 167         ra->request_update = &iio_request_update_sw_rb;
 168
 169         ra->get_bpd = &iio_get_bpd_sw_rb;
 170         ra->set_bpd = &iio_set_bpd_sw_rb;
 171
 172         ra->get_length = &iio_get_length_sw_rb;
 173         ra->set_length = &iio_set_length_sw_rb;
 174 };
 175
 176 /**
 177  * struct iio_sw_ring_buffer - software ring buffer
 178  * @buf:                generic ring buffer elements
 179  * @data:               the ring buffer memory
 180  * @read_p:             read pointer (oldest available)
 181  * @write_p:            write pointer
 182  * @last_written_p:     read pointer (newest available)
 183  * @half_p:             half buffer length behind write_p (event generation)
 184  * @use_count:          reference count to prevent resizing when in use
 185  * @update_needed:      flag to indicated change in size requested
 186  * @use_lock:           lock to prevent change in size when in use
 187  *
 188  * Note that the first element of all ring buffers must be a
 189  * struct iio_ring_buffer.
 190 **/
 191
 192 struct iio_sw_ring_buffer {
 193         struct iio_ring_buffer  buf;
 194         unsigned char           *data;
 195         unsigned char           *read_p;
 196         unsigned char           *write_p;
 197         unsigned char           *last_written_p;
 198         /* used to act as a point at which to signal an event */
 199         unsigned char           *half_p;
 200         int                     use_count;
 201         int                     update_needed;
 202         spinlock_t              use_lock;
 203 };
 204
 205 #define iio_to_sw_ring(r) container_of(r, struct iio_sw_ring_buffer, buf)
 206
 207 struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev);
 208 void iio_sw_rb_free(struct iio_ring_buffer *ring);
 209
 210 int iio_sw_ring_preenable(struct iio_dev *indio_dev);
 211
 212 struct iio_sw_ring_helper_state {
 213         struct work_struct              work_trigger_to_ring;
 214         struct iio_dev                  *indio_dev;
 215         int (*get_ring_element)(struct iio_sw_ring_helper_state *st, u8 *buf);
 216         s64                             last_timestamp;
 217 };
 218
 219 void iio_sw_poll_func_th(struct iio_dev *indio_dev, s64 time);
 220 void iio_sw_trigger_bh_to_ring(struct work_struct *work_s);
 221
 222 #else /* CONFIG_IIO_RING_BUFFER*/
 223 struct iio_sw_ring_helper_state {
 224         struct iio_dev                  *indio_dev;
 225 };
 226 #endif /* !CONFIG_IIO_RING_BUFFER */
 227 #endif /* _IIO_RING_SW_H_ */