lib/ringbuffer/backend.h

   1 #ifndef _LINUX_RING_BUFFER_BACKEND_H
   2 #define _LINUX_RING_BUFFER_BACKEND_H
   3
   4 /*
   5  * linux/ringbuffer/backend.h
   6  *
   7  * Copyright (C) 2008-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Ring buffer backend (API).
  10  *
  11  * Dual LGPL v2.1/GPL v2 license.
  12  *
  13  * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
  14  * the reader in flight recorder mode.
  15  */
  16
  17 #include <linux/types.h>
  18 #include <linux/sched.h>
  19 #include <linux/timer.h>
  20 #include <linux/wait.h>
  21 #include <linux/poll.h>
  22 #include <linux/list.h>
  23 #include <linux/fs.h>
  24 #include <linux/mm.h>
  25
  26 /* Internal helpers */
  27 #include "../../wrapper/ringbuffer/backend_internal.h"
  28 #include "../../wrapper/ringbuffer/frontend_internal.h"
  29
  30 /* Ring buffer backend API */
  31
  32 /* Ring buffer backend access (read/write) */
  33
  34 extern size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb,
  35                                    size_t offset, void *dest, size_t len);
  36
  37 extern int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend *bufb,
  38                                           size_t offset, void __user *dest,
  39                                           size_t len);
  40
  41 extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb,
  42                                      size_t offset, void *dest, size_t len);
  43
  44 extern struct page **
  45 lib_ring_buffer_read_get_page(struct lib_ring_buffer_backend *bufb, size_t offset,
  46                               void ***virt);
  47
  48 /*
  49  * Return the address where a given offset is located.
  50  * Should be used to get the current subbuffer header pointer. Given we know
  51  * it's never on a page boundary, it's safe to write directly to this address,
  52  * as long as the write is never bigger than a page size.
  53  */
  54 extern void *
  55 lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb,
  56                                size_t offset);
  57 extern void *
  58 lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb,
  59                                     size_t offset);
  60
  61 /**
  62  * lib_ring_buffer_write - write data to a buffer backend
  63  * @config : ring buffer instance configuration
  64  * @ctx: ring buffer context. (input arguments only)
  65  * @src : source pointer to copy from
  66  * @len : length of data to copy
  67  *
  68  * This function copies "len" bytes of data from a source pointer to a buffer
  69  * backend, at the current context offset. This is more or less a buffer
  70  * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)
  71  * if copy is crossing a page boundary.
  72  */
  73 static inline
  74 void lib_ring_buffer_write(const struct lib_ring_buffer_config *config,
  75                            struct lib_ring_buffer_ctx *ctx,
  76                            const void *src, size_t len)
  77 {
  78         struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
  79         struct channel_backend *chanb = &ctx->chan->backend;
  80         size_t sbidx, index;
  81         size_t offset = ctx->buf_offset;
  82         ssize_t pagecpy;
  83         struct lib_ring_buffer_backend_pages *rpages;
  84         unsigned long sb_bindex, id;
  85
  86         offset &= chanb->buf_size - 1;
  87         sbidx = offset >> chanb->subbuf_size_order;
  88         index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
  89         pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
  90         id = bufb->buf_wsb[sbidx].id;
  91         sb_bindex = subbuffer_id_get_index(config, id);
  92         rpages = bufb->array[sb_bindex];
  93         CHAN_WARN_ON(ctx->chan,
  94                      config->mode == RING_BUFFER_OVERWRITE
  95                      && subbuffer_id_is_noref(config, id));
  96         if (likely(pagecpy == len))
  97                 lib_ring_buffer_do_copy(config,
  98                                         rpages->p[index].virt
  99                                             + (offset & ~PAGE_MASK),
 100                                         src, len);
 101         else
 102                 _lib_ring_buffer_write(bufb, offset, src, len, 0);
 103         ctx->buf_offset += len;
 104 }
 105
 106 /*
 107  * This accessor counts the number of unread records in a buffer.
 108  * It only provides a consistent value if no reads not writes are performed
 109  * concurrently.
 110  */
 111 static inline
 112 unsigned long lib_ring_buffer_get_records_unread(
 113                                 const struct lib_ring_buffer_config *config,
 114                                 struct lib_ring_buffer *buf)
 115 {
 116         struct lib_ring_buffer_backend *bufb = &buf->backend;
 117         struct lib_ring_buffer_backend_pages *pages;
 118         unsigned long records_unread = 0, sb_bindex, id;
 119         unsigned int i;
 120
 121         for (i = 0; i < bufb->chan->backend.num_subbuf; i++) {
 122                 id = bufb->buf_wsb[i].id;
 123                 sb_bindex = subbuffer_id_get_index(config, id);
 124                 pages = bufb->array[sb_bindex];
 125                 records_unread += v_read(config, &pages->records_unread);
 126         }
 127         if (config->mode == RING_BUFFER_OVERWRITE) {
 128                 id = bufb->buf_rsb.id;
 129                 sb_bindex = subbuffer_id_get_index(config, id);
 130                 pages = bufb->array[sb_bindex];
 131                 records_unread += v_read(config, &pages->records_unread);
 132         }
 133         return records_unread;
 134 }
 135
 136 ssize_t lib_ring_buffer_file_splice_read(struct file *in, loff_t *ppos,
 137                                          struct pipe_inode_info *pipe,
 138                                          size_t len, unsigned int flags);
 139 loff_t lib_ring_buffer_no_llseek(struct file *file, loff_t offset, int origin);
 140
 141 #endif /* _LINUX_RING_BUFFER_BACKEND_H */