include/lttng/ust-ctl.h

   1 /*
   2  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
   3  * Copyright (C) 2011-2013 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; version 2 of the License only.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #ifndef _LTTNG_UST_CTL_H
  20 #define _LTTNG_UST_CTL_H
  21
  22 #include <limits.h>
  23 #include <stddef.h>
  24 #include <stdint.h>
  25 #include <sys/types.h>
  26
  27 #include <lttng/ust-abi.h>
  28
  29 #ifndef LTTNG_PACKED
  30 #error "LTTNG_PACKED should be defined"
  31 #endif
  32
  33 #ifndef LTTNG_UST_UUID_LEN
  34 #define LTTNG_UST_UUID_LEN      16
  35 #endif
  36
  37 /* Default unix socket path */
  38 #define LTTNG_UST_SOCK_FILENAME                                 \
  39         "lttng-ust-sock-"                                       \
  40         __ust_stringify(LTTNG_UST_ABI_MAJOR_VERSION)
  41
  42 /*
  43  * Shared memory files path are automatically related to shm root, e.g.
  44  * /dev/shm under linux.
  45  */
  46 #define LTTNG_UST_WAIT_FILENAME                                 \
  47         "lttng-ust-wait-"                                       \
  48         __ust_stringify(LTTNG_UST_ABI_MAJOR_VERSION)
  49
  50 struct lttng_ust_shm_handle;
  51 struct lttng_ust_lib_ring_buffer;
  52
  53 struct ustctl_consumer_channel_attr {
  54         enum lttng_ust_chan_type type;
  55         uint64_t subbuf_size;                   /* bytes */
  56         uint64_t num_subbuf;                    /* power of 2 */
  57         int overwrite;                          /* 1: overwrite, 0: discard */
  58         unsigned int switch_timer_interval;     /* usec */
  59         unsigned int read_timer_interval;       /* usec */
  60         enum lttng_ust_output output;           /* splice, mmap */
  61         uint32_t chan_id;                       /* channel ID */
  62         unsigned char uuid[LTTNG_UST_UUID_LEN]; /* Trace session unique ID */
  63         int64_t blocking_timeout;                       /* Blocking timeout (usec) */
  64 } LTTNG_PACKED;
  65
  66 /*
  67  * API used by sessiond.
  68  */
  69
  70 struct lttng_ust_context_attr {
  71         enum lttng_ust_context_type ctx;
  72         union {
  73                 struct lttng_ust_perf_counter_ctx perf_counter;
  74                 struct {
  75                         char *provider_name;
  76                         char *ctx_name;
  77                 } app_ctx;
  78         } u;
  79 };
  80
  81 /*
  82  * Error values: all the following functions return:
  83  * >= 0: Success (LTTNG_UST_OK)
  84  * < 0: error code.
  85  */
  86 int ustctl_register_done(int sock);
  87 int ustctl_create_session(int sock);
  88 int ustctl_create_event(int sock, struct lttng_ust_event *ev,
  89                 struct lttng_ust_object_data *channel_data,
  90                 struct lttng_ust_object_data **event_data);
  91 int ustctl_add_context(int sock, struct lttng_ust_context_attr *ctx,
  92                 struct lttng_ust_object_data *obj_data,
  93                 struct lttng_ust_object_data **context_data);
  94 int ustctl_set_filter(int sock, struct lttng_ust_filter_bytecode *bytecode,
  95                 struct lttng_ust_object_data *obj_data);
  96 int ustctl_set_exclusion(int sock, struct lttng_ust_event_exclusion *exclusion,
  97                 struct lttng_ust_object_data *obj_data);
  98
  99 int ustctl_enable(int sock, struct lttng_ust_object_data *object);
 100 int ustctl_disable(int sock, struct lttng_ust_object_data *object);
 101 int ustctl_start_session(int sock, int handle);
 102 int ustctl_stop_session(int sock, int handle);
 103
 104 /*
 105  * ustctl_create_event notifier_group creates a event notifier group. It
 106  * establishes the connection with the application by providing a file
 107  * descriptor of the pipe to be used by the application when a event notifier
 108  * of that group is fired. It returns a handle to be used when creating event
 109  * notifier in that group.
 110  */
 111 int ustctl_create_event_notifier_group(int sock, int pipe_fd,
 112                 struct lttng_ust_object_data **event_notifier_group);
 113
 114 /*
 115  * ustctl_create_event notifier creates a event notifier in a event notifier
 116  * group giving a event notifier description and a event notifier group handle.
 117  * It returns a event notifier handle to be used when enabling the event
 118  * notifier, attaching filter, attaching exclusion, and disabling the event
 119  * notifier.
 120  */
 121 int ustctl_create_event_notifier(int sock,
 122                 struct lttng_ust_event_notifier *event_notifier,
 123                 struct lttng_ust_object_data *event_notifier_group,
 124                 struct lttng_ust_object_data **event_notifier_data);
 125
 126 /*
 127  * ustctl_tracepoint_list returns a tracepoint list handle, or negative
 128  * error value.
 129  */
 130 int ustctl_tracepoint_list(int sock);
 131
 132 /*
 133  * ustctl_tracepoint_list_get is used to iterate on the tp list
 134  * handle. End is iteration is reached when -LTTNG_UST_ERR_NOENT is
 135  * returned.
 136  */
 137 int ustctl_tracepoint_list_get(int sock, int tp_list_handle,
 138                 struct lttng_ust_tracepoint_iter *iter);
 139
 140 /*
 141  * ustctl_tracepoint_field_list returns a tracepoint field list handle,
 142  * or negative error value.
 143  */
 144 int ustctl_tracepoint_field_list(int sock);
 145
 146 /*
 147  * ustctl_tracepoint_field_list_get is used to iterate on the tp field
 148  * list handle. End is iteration is reached when -LTTNG_UST_ERR_NOENT is
 149  * returned.
 150  */
 151 int ustctl_tracepoint_field_list_get(int sock, int tp_field_list_handle,
 152                 struct lttng_ust_field_iter *iter);
 153
 154 int ustctl_tracer_version(int sock, struct lttng_ust_tracer_version *v);
 155 int ustctl_wait_quiescent(int sock);
 156
 157 int ustctl_sock_flush_buffer(int sock, struct lttng_ust_object_data *object);
 158
 159 int ustctl_calibrate(int sock, struct lttng_ust_calibrate *calibrate);
 160
 161 /* Release object created by members of this API. */
 162 int ustctl_release_object(int sock, struct lttng_ust_object_data *data);
 163 /* Release handle returned by create session. */
 164 int ustctl_release_handle(int sock, int handle);
 165
 166 int ustctl_recv_channel_from_consumer(int sock,
 167                 struct lttng_ust_object_data **channel_data);
 168 int ustctl_recv_stream_from_consumer(int sock,
 169                 struct lttng_ust_object_data **stream_data);
 170 int ustctl_send_channel_to_ust(int sock, int session_handle,
 171                 struct lttng_ust_object_data *channel_data);
 172 int ustctl_send_stream_to_ust(int sock,
 173                 struct lttng_ust_object_data *channel_data,
 174                 struct lttng_ust_object_data *stream_data);
 175
 176 /*
 177  * ustctl_duplicate_ust_object_data allocated a new object in "dest" if
 178  * it succeeds (returns 0). It must be released using
 179  * ustctl_release_object() and then freed with free().
 180  */
 181 int ustctl_duplicate_ust_object_data(struct lttng_ust_object_data **dest,
 182                 struct lttng_ust_object_data *src);
 183
 184 /*
 185  * API used by consumer.
 186  */
 187
 188 struct ustctl_consumer_channel;
 189 struct ustctl_consumer_stream;
 190 struct ustctl_consumer_channel_attr;
 191
 192 int ustctl_get_nr_stream_per_channel(void);
 193
 194 struct ustctl_consumer_channel *
 195         ustctl_create_channel(struct ustctl_consumer_channel_attr *attr,
 196                 const int *stream_fds, int nr_stream_fds);
 197 /*
 198  * Each stream created needs to be destroyed before calling
 199  * ustctl_destroy_channel().
 200  */
 201 void ustctl_destroy_channel(struct ustctl_consumer_channel *chan);
 202
 203 int ustctl_send_channel_to_sessiond(int sock,
 204                 struct ustctl_consumer_channel *channel);
 205 int ustctl_channel_close_wait_fd(struct ustctl_consumer_channel *consumer_chan);
 206 int ustctl_channel_close_wakeup_fd(struct ustctl_consumer_channel *consumer_chan);
 207 int ustctl_channel_get_wait_fd(struct ustctl_consumer_channel *consumer_chan);
 208 int ustctl_channel_get_wakeup_fd(struct ustctl_consumer_channel *consumer_chan);
 209
 210 int ustctl_write_metadata_to_channel(
 211                 struct ustctl_consumer_channel *channel,
 212                 const char *metadata_str,       /* NOT null-terminated */
 213                 size_t len);                    /* metadata length */
 214 ssize_t ustctl_write_one_packet_to_channel(
 215                 struct ustctl_consumer_channel *channel,
 216                 const char *metadata_str,       /* NOT null-terminated */
 217                 size_t len);                    /* metadata length */
 218
 219 /*
 220  * Send a NULL stream to finish iteration over all streams of a given
 221  * channel.
 222  */
 223 int ustctl_send_stream_to_sessiond(int sock,
 224                 struct ustctl_consumer_stream *stream);
 225 int ustctl_stream_close_wait_fd(struct ustctl_consumer_stream *stream);
 226 int ustctl_stream_close_wakeup_fd(struct ustctl_consumer_stream *stream);
 227 int ustctl_stream_get_wait_fd(struct ustctl_consumer_stream *stream);
 228 int ustctl_stream_get_wakeup_fd(struct ustctl_consumer_stream *stream);
 229
 230 /* Create/destroy stream buffers for read */
 231 struct ustctl_consumer_stream *
 232         ustctl_create_stream(struct ustctl_consumer_channel *channel,
 233                         int cpu);
 234 void ustctl_destroy_stream(struct ustctl_consumer_stream *stream);
 235
 236 /* For mmap mode, readable without "get" operation */
 237 int ustctl_get_mmap_len(struct ustctl_consumer_stream *stream,
 238                 unsigned long *len);
 239 int ustctl_get_max_subbuf_size(struct ustctl_consumer_stream *stream,
 240                 unsigned long *len);
 241
 242 /*
 243  * For mmap mode, operate on the current packet (between get/put or
 244  * get_next/put_next).
 245  */
 246 void *ustctl_get_mmap_base(struct ustctl_consumer_stream *stream);
 247 int ustctl_get_mmap_read_offset(struct ustctl_consumer_stream *stream,
 248                 unsigned long *off);
 249 int ustctl_get_subbuf_size(struct ustctl_consumer_stream *stream,
 250                 unsigned long *len);
 251 int ustctl_get_padded_subbuf_size(struct ustctl_consumer_stream *stream,
 252                 unsigned long *len);
 253 int ustctl_get_next_subbuf(struct ustctl_consumer_stream *stream);
 254 int ustctl_put_next_subbuf(struct ustctl_consumer_stream *stream);
 255
 256 /* snapshot */
 257
 258 int ustctl_snapshot(struct ustctl_consumer_stream *stream);
 259 int ustctl_snapshot_sample_positions(struct ustctl_consumer_stream *stream);
 260 int ustctl_snapshot_get_consumed(struct ustctl_consumer_stream *stream,
 261                 unsigned long *pos);
 262 int ustctl_snapshot_get_produced(struct ustctl_consumer_stream *stream,
 263                 unsigned long *pos);
 264 int ustctl_get_subbuf(struct ustctl_consumer_stream *stream,
 265                 unsigned long *pos);
 266 int ustctl_put_subbuf(struct ustctl_consumer_stream *stream);
 267
 268 void ustctl_flush_buffer(struct ustctl_consumer_stream *stream,
 269                 int producer_active);
 270 void ustctl_clear_buffer(struct ustctl_consumer_stream *stream);
 271
 272 /* index */
 273
 274 /*
 275  * Getters which need to be used on the current packet (between get/put
 276  * or get_next/put_next.
 277  */
 278
 279 int ustctl_get_timestamp_begin(struct ustctl_consumer_stream *stream,
 280                 uint64_t *timestamp_begin);
 281 int ustctl_get_timestamp_end(struct ustctl_consumer_stream *stream,
 282         uint64_t *timestamp_end);
 283 int ustctl_get_events_discarded(struct ustctl_consumer_stream *stream,
 284         uint64_t *events_discarded);
 285 int ustctl_get_content_size(struct ustctl_consumer_stream *stream,
 286         uint64_t *content_size);
 287 int ustctl_get_packet_size(struct ustctl_consumer_stream *stream,
 288         uint64_t *packet_size);
 289 int ustctl_get_sequence_number(struct ustctl_consumer_stream *stream,
 290                 uint64_t *seq);
 291
 292 /*
 293  * Getter returning state invariant for the stream, which can be used
 294  * without "get" operation.
 295  */
 296
 297 int ustctl_get_stream_id(struct ustctl_consumer_stream *stream,
 298                 uint64_t *stream_id);
 299 int ustctl_get_instance_id(struct ustctl_consumer_stream *stream,
 300                 uint64_t *id);
 301
 302 /*
 303  * Getter returning the current timestamp as perceived from the
 304  * tracer.
 305  */
 306 int ustctl_get_current_timestamp(struct ustctl_consumer_stream *stream,
 307                 uint64_t *ts);
 308
 309 /* returns whether UST has perf counters support. */
 310 int ustctl_has_perf_counters(void);
 311
 312 /* Regenerate the statedump. */
 313 int ustctl_regenerate_statedump(int sock, int handle);
 314
 315 /* event registry management */
 316
 317 enum ustctl_socket_type {
 318         USTCTL_SOCKET_CMD = 0,
 319         USTCTL_SOCKET_NOTIFY = 1,
 320 };
 321
 322 enum ustctl_notify_cmd {
 323         USTCTL_NOTIFY_CMD_EVENT = 0,
 324         USTCTL_NOTIFY_CMD_CHANNEL = 1,
 325         USTCTL_NOTIFY_CMD_ENUM = 2,
 326 };
 327
 328 enum ustctl_channel_header {
 329         USTCTL_CHANNEL_HEADER_UNKNOWN = 0,
 330         USTCTL_CHANNEL_HEADER_COMPACT = 1,
 331         USTCTL_CHANNEL_HEADER_LARGE = 2,
 332 };
 333
 334 /* event type structures */
 335
 336 enum ustctl_abstract_types {
 337         ustctl_atype_integer,
 338         ustctl_atype_enum,      /* legacy */
 339         ustctl_atype_array,     /* legacy */
 340         ustctl_atype_sequence,  /* legacy */
 341         ustctl_atype_string,
 342         ustctl_atype_float,
 343         ustctl_atype_variant,   /* legacy */
 344         ustctl_atype_struct,    /* legacy */
 345         ustctl_atype_enum_nestable,
 346         ustctl_atype_array_nestable,
 347         ustctl_atype_sequence_nestable,
 348         ustctl_atype_struct_nestable,
 349         ustctl_atype_variant_nestable,
 350         NR_USTCTL_ABSTRACT_TYPES,
 351 };
 352
 353 enum ustctl_string_encodings {
 354         ustctl_encode_none = 0,
 355         ustctl_encode_UTF8 = 1,
 356         ustctl_encode_ASCII = 2,
 357         NR_USTCTL_STRING_ENCODINGS,
 358 };
 359
 360 #define USTCTL_UST_INTEGER_TYPE_PADDING 24
 361 struct ustctl_integer_type {
 362         uint32_t size;          /* in bits */
 363         uint32_t signedness;
 364         uint32_t reverse_byte_order;
 365         uint32_t base;          /* 2, 8, 10, 16, for pretty print */
 366         int32_t encoding;       /* enum ustctl_string_encodings */
 367         uint16_t alignment;     /* in bits */
 368         char padding[USTCTL_UST_INTEGER_TYPE_PADDING];
 369 } LTTNG_PACKED;
 370
 371 #define USTCTL_UST_FLOAT_TYPE_PADDING   24
 372 struct ustctl_float_type {
 373         uint32_t exp_dig;               /* exponent digits, in bits */
 374         uint32_t mant_dig;              /* mantissa digits, in bits */
 375         uint32_t reverse_byte_order;
 376         uint16_t alignment;     /* in bits */
 377         char padding[USTCTL_UST_FLOAT_TYPE_PADDING];
 378 } LTTNG_PACKED;
 379
 380 #define USTCTL_UST_ENUM_VALUE_PADDING   15
 381 struct ustctl_enum_value {
 382         uint64_t value;
 383         uint8_t signedness;
 384         char padding[USTCTL_UST_ENUM_VALUE_PADDING];
 385 } LTTNG_PACKED;
 386
 387 enum ustctl_ust_enum_entry_options {
 388         USTCTL_UST_ENUM_ENTRY_OPTION_IS_AUTO = 1U << 0,
 389 };
 390
 391 #define USTCTL_UST_ENUM_ENTRY_PADDING   32
 392 struct ustctl_enum_entry {
 393         struct ustctl_enum_value start, end; /* start and end are inclusive */
 394         char string[LTTNG_UST_SYM_NAME_LEN];
 395         union {
 396                 struct {
 397                         uint32_t options;
 398                 } LTTNG_PACKED extra;
 399                 char padding[USTCTL_UST_ENUM_ENTRY_PADDING];
 400         } u;
 401 } LTTNG_PACKED;
 402
 403 /* legacy */
 404 #define USTCTL_UST_BASIC_TYPE_PADDING   296
 405 union _ustctl_basic_type {
 406         struct ustctl_integer_type integer;
 407         struct {
 408                 char name[LTTNG_UST_SYM_NAME_LEN];
 409                 struct ustctl_integer_type container_type;
 410                 uint64_t id;    /* enum ID in sessiond. */
 411         } enumeration;
 412         struct {
 413                 int32_t encoding;       /* enum ustctl_string_encodings */
 414         } string;
 415         struct ustctl_float_type _float;
 416         char padding[USTCTL_UST_BASIC_TYPE_PADDING];
 417 } LTTNG_PACKED;
 418
 419 /* legacy */
 420 struct ustctl_basic_type {
 421         enum ustctl_abstract_types atype;
 422         union {
 423                 union _ustctl_basic_type basic;
 424         } u;
 425 } LTTNG_PACKED;
 426
 427 /*
 428  * Padding is derived from largest member: u.legacy.sequence which
 429  * contains two basic types, each with USTCTL_UST_BASIC_TYPE_PADDING.
 430  */
 431 #define USTCTL_UST_TYPE_PADDING (2 * USTCTL_UST_BASIC_TYPE_PADDING)
 432 struct ustctl_type {
 433         enum ustctl_abstract_types atype;
 434         union {
 435                 struct ustctl_integer_type integer;
 436                 struct ustctl_float_type _float;
 437                 struct {
 438                         int32_t encoding;       /* enum ustctl_string_encodings */
 439                 } string;
 440                 struct {
 441                         char name[LTTNG_UST_SYM_NAME_LEN];
 442                         uint64_t id;    /* enum ID in sessiond. */
 443                         /* container_type follows after this struct ustctl_field. */
 444                 } enum_nestable;
 445                 struct {
 446                         uint32_t length;                /* num. elems. */
 447                         uint32_t alignment;
 448                         /* elem_type follows after this struct ustctl_field. */
 449                 } array_nestable;
 450                 struct {
 451                         char length_name[LTTNG_UST_SYM_NAME_LEN];
 452                         uint32_t alignment;             /* Alignment before elements. */
 453                         /* elem_type follows after the length_type. */
 454                 } sequence_nestable;
 455                 struct {
 456                         uint32_t nr_fields;
 457                         uint32_t alignment;
 458                         /* Followed by nr_fields struct ustctl_field. */
 459                 } struct_nestable;
 460                 struct {
 461                         uint32_t nr_choices;
 462                         char tag_name[LTTNG_UST_SYM_NAME_LEN];
 463                         uint32_t alignment;
 464                         /* Followed by nr_choices struct ustctl_field. */
 465                 } variant_nestable;
 466
 467                 /* Legacy ABI */
 468                 union {
 469                         union _ustctl_basic_type basic;
 470                         struct {
 471                                 struct ustctl_basic_type elem_type;
 472                                 uint32_t length;                /* num. elems. */
 473                         } array;
 474                         struct {
 475                                 struct ustctl_basic_type length_type;
 476                                 struct ustctl_basic_type elem_type;
 477                         } sequence;
 478                         struct {
 479                                 uint32_t nr_fields;
 480                                 /* Followed by nr_fields struct ustctl_field. */
 481                         } _struct;
 482                         struct {
 483                                 uint32_t nr_choices;
 484                                 char tag_name[LTTNG_UST_SYM_NAME_LEN];
 485                                 /* Followed by nr_choices struct ustctl_field. */
 486                         } variant;
 487                 } legacy;
 488                 char padding[USTCTL_UST_TYPE_PADDING];
 489         } u;
 490 } LTTNG_PACKED;
 491
 492 #define USTCTL_UST_FIELD_PADDING        28
 493 struct ustctl_field {
 494         char name[LTTNG_UST_SYM_NAME_LEN];
 495         struct ustctl_type type;
 496         char padding[USTCTL_UST_FIELD_PADDING];
 497 } LTTNG_PACKED;
 498
 499 /*
 500  * Returns 0 on success, negative error value on error.
 501  * If an error other than -LTTNG_UST_ERR_UNSUP_MAJOR is returned,
 502  * the output fields are not populated.
 503  */
 504 int ustctl_recv_reg_msg(int sock,
 505         enum ustctl_socket_type *type,
 506         uint32_t *major,
 507         uint32_t *minor,
 508         uint32_t *pid,
 509         uint32_t *ppid,
 510         uint32_t *uid,
 511         uint32_t *gid,
 512         uint32_t *bits_per_long,
 513         uint32_t *uint8_t_alignment,
 514         uint32_t *uint16_t_alignment,
 515         uint32_t *uint32_t_alignment,
 516         uint32_t *uint64_t_alignment,
 517         uint32_t *long_alignment,
 518         int *byte_order,
 519         char *name);    /* size LTTNG_UST_ABI_PROCNAME_LEN */
 520
 521 /*
 522  * Returns 0 on success, negative UST or system error value on error.
 523  * Receive the notification command. The "notify_cmd" can then be used
 524  * by the caller to find out which ustctl_recv_* function should be
 525  * called to receive the notification, and which ustctl_reply_* is
 526  * appropriate.
 527  */
 528 int ustctl_recv_notify(int sock, enum ustctl_notify_cmd *notify_cmd);
 529
 530 /*
 531  * Returns 0 on success, negative UST or system error value on error.
 532  */
 533 int ustctl_recv_register_event(int sock,
 534         int *session_objd,              /* session descriptor (output) */
 535         int *channel_objd,              /* channel descriptor (output) */
 536         char *event_name,               /*
 537                                          * event name (output,
 538                                          * size LTTNG_UST_SYM_NAME_LEN)
 539                                          */
 540         int *loglevel,
 541         char **signature,               /*
 542                                          * event signature
 543                                          * (output, dynamically
 544                                          * allocated, must be free(3)'d
 545                                          * by the caller if function
 546                                          * returns success.)
 547                                          */
 548         size_t *nr_fields,
 549         struct ustctl_field **fields,
 550         char **model_emf_uri);
 551
 552 /*
 553  * Returns 0 on success, negative error value on error.
 554  */
 555 int ustctl_reply_register_event(int sock,
 556         uint32_t id,                    /* event id (input) */
 557         int ret_code);                  /* return code. 0 ok, negative error */
 558
 559 /*
 560  * Returns 0 on success, negative UST or system error value on error.
 561  */
 562 int ustctl_recv_register_enum(int sock,
 563         int *session_objd,
 564         char *enum_name,
 565         struct ustctl_enum_entry **entries,
 566         size_t *nr_entries);
 567
 568 /*
 569  * Returns 0 on success, negative error value on error.
 570  */
 571 int ustctl_reply_register_enum(int sock,
 572         uint64_t id,                    /* enum id (input) */
 573         int ret_code);
 574
 575 /*
 576  * Returns 0 on success, negative UST or system error value on error.
 577  */
 578 int ustctl_recv_register_channel(int sock,
 579         int *session_objd,              /* session descriptor (output) */
 580         int *channel_objd,              /* channel descriptor (output) */
 581         size_t *nr_fields,              /* context fields */
 582         struct ustctl_field **fields);
 583
 584 /*
 585  * Returns 0 on success, negative error value on error.
 586  */
 587 int ustctl_reply_register_channel(int sock,
 588         uint32_t chan_id,
 589         enum ustctl_channel_header header_type,
 590         int ret_code);                  /* return code. 0 ok, negative error */
 591
 592 #endif /* _LTTNG_UST_CTL_H */