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852c2936 MD |
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 | ||
852c2936 | 17 | /* Internal helpers */ |
4931a13e MD |
18 | #include "backend_internal.h" |
19 | #include "frontend_internal.h" | |
852c2936 MD |
20 | |
21 | /* Ring buffer backend API */ | |
22 | ||
23 | /* Ring buffer backend access (read/write) */ | |
24 | ||
25 | extern size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb, | |
26 | size_t offset, void *dest, size_t len); | |
27 | ||
28 | extern int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend *bufb, | |
29 | size_t offset, void __user *dest, | |
30 | size_t len); | |
31 | ||
32 | extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb, | |
33 | size_t offset, void *dest, size_t len); | |
34 | ||
35 | extern struct page ** | |
36 | lib_ring_buffer_read_get_page(struct lib_ring_buffer_backend *bufb, size_t offset, | |
37 | void ***virt); | |
38 | ||
39 | /* | |
40 | * Return the address where a given offset is located. | |
41 | * Should be used to get the current subbuffer header pointer. Given we know | |
42 | * it's never on a page boundary, it's safe to write directly to this address, | |
43 | * as long as the write is never bigger than a page size. | |
44 | */ | |
45 | extern void * | |
46 | lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb, | |
47 | size_t offset); | |
48 | extern void * | |
49 | lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb, | |
50 | size_t offset); | |
51 | ||
52 | /** | |
53 | * lib_ring_buffer_write - write data to a buffer backend | |
54 | * @config : ring buffer instance configuration | |
55 | * @ctx: ring buffer context. (input arguments only) | |
56 | * @src : source pointer to copy from | |
57 | * @len : length of data to copy | |
58 | * | |
59 | * This function copies "len" bytes of data from a source pointer to a buffer | |
60 | * backend, at the current context offset. This is more or less a buffer | |
61 | * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write) | |
62 | * if copy is crossing a page boundary. | |
63 | */ | |
64 | static inline | |
65 | void lib_ring_buffer_write(const struct lib_ring_buffer_config *config, | |
66 | struct lib_ring_buffer_ctx *ctx, | |
67 | const void *src, size_t len) | |
68 | { | |
69 | struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; | |
70 | struct channel_backend *chanb = &ctx->chan->backend; | |
71 | size_t sbidx, index; | |
72 | size_t offset = ctx->buf_offset; | |
73 | ssize_t pagecpy; | |
74 | struct lib_ring_buffer_backend_pages *rpages; | |
75 | unsigned long sb_bindex, id; | |
76 | ||
77 | offset &= chanb->buf_size - 1; | |
78 | sbidx = offset >> chanb->subbuf_size_order; | |
79 | index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; | |
80 | pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); | |
81 | id = bufb->buf_wsb[sbidx].id; | |
82 | sb_bindex = subbuffer_id_get_index(config, id); | |
83 | rpages = bufb->array[sb_bindex]; | |
84 | CHAN_WARN_ON(ctx->chan, | |
85 | config->mode == RING_BUFFER_OVERWRITE | |
86 | && subbuffer_id_is_noref(config, id)); | |
87 | if (likely(pagecpy == len)) | |
88 | lib_ring_buffer_do_copy(config, | |
89 | rpages->p[index].virt | |
90 | + (offset & ~PAGE_MASK), | |
91 | src, len); | |
92 | else | |
93 | _lib_ring_buffer_write(bufb, offset, src, len, 0); | |
94 | ctx->buf_offset += len; | |
95 | } | |
96 | ||
97 | /* | |
98 | * This accessor counts the number of unread records in a buffer. | |
99 | * It only provides a consistent value if no reads not writes are performed | |
100 | * concurrently. | |
101 | */ | |
102 | static inline | |
103 | unsigned long lib_ring_buffer_get_records_unread( | |
104 | const struct lib_ring_buffer_config *config, | |
105 | struct lib_ring_buffer *buf) | |
106 | { | |
107 | struct lib_ring_buffer_backend *bufb = &buf->backend; | |
108 | struct lib_ring_buffer_backend_pages *pages; | |
109 | unsigned long records_unread = 0, sb_bindex, id; | |
110 | unsigned int i; | |
111 | ||
112 | for (i = 0; i < bufb->chan->backend.num_subbuf; i++) { | |
113 | id = bufb->buf_wsb[i].id; | |
114 | sb_bindex = subbuffer_id_get_index(config, id); | |
115 | pages = bufb->array[sb_bindex]; | |
116 | records_unread += v_read(config, &pages->records_unread); | |
117 | } | |
118 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
119 | id = bufb->buf_rsb.id; | |
120 | sb_bindex = subbuffer_id_get_index(config, id); | |
121 | pages = bufb->array[sb_bindex]; | |
122 | records_unread += v_read(config, &pages->records_unread); | |
123 | } | |
124 | return records_unread; | |
125 | } | |
126 | ||
127 | ssize_t lib_ring_buffer_file_splice_read(struct file *in, loff_t *ppos, | |
128 | struct pipe_inode_info *pipe, | |
129 | size_t len, unsigned int flags); | |
130 | loff_t lib_ring_buffer_no_llseek(struct file *file, loff_t offset, int origin); | |
131 | ||
132 | #endif /* _LINUX_RING_BUFFER_BACKEND_H */ |