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_capture(int sock, struct lttng_ust_capture_bytecode *bytecode,
  97                 struct lttng_ust_object_data *obj_data);
  98 int ustctl_set_exclusion(int sock, struct lttng_ust_event_exclusion *exclusion,
  99                 struct lttng_ust_object_data *obj_data);
 100
 101 int ustctl_enable(int sock, struct lttng_ust_object_data *object);
 102 int ustctl_disable(int sock, struct lttng_ust_object_data *object);
 103 int ustctl_start_session(int sock, int handle);
 104 int ustctl_stop_session(int sock, int handle);
 105
 106 /*
 107  * ustctl_create_trigger_group creates a trigger group. It establishes the
 108  * connection with the application by providing a file descriptor of the pipe
 109  * to be used by the application when a trigger of that group is fired. It
 110  * returns a handle to be used when creating trigger in that group.
 111  */
 112 int ustctl_create_trigger_group(int sock, int pipe_fd,
 113                 struct lttng_ust_object_data **trigger_group);
 114
 115 /*
 116  * ustctl_create_trigger creates a trigger in a trigger group giving a trigger
 117  * description and a trigger group handle. It returns a trigger handle to be
 118  * used when enabling the trigger, attaching filter, attaching exclusion, and
 119  * disabling the trigger.
 120  */
 121 int ustctl_create_trigger(int sock, struct lttng_ust_trigger *trigger,
 122                 struct lttng_ust_object_data *trigger_group,
 123                 struct lttng_ust_object_data **trigger_data);
 124
 125 /*
 126  * ustctl_tracepoint_list returns a tracepoint list handle, or negative
 127  * error value.
 128  */
 129 int ustctl_tracepoint_list(int sock);
 130
 131 /*
 132  * ustctl_tracepoint_list_get is used to iterate on the tp list
 133  * handle. End is iteration is reached when -LTTNG_UST_ERR_NOENT is
 134  * returned.
 135  */
 136 int ustctl_tracepoint_list_get(int sock, int tp_list_handle,
 137                 struct lttng_ust_tracepoint_iter *iter);
 138
 139 /*
 140  * ustctl_tracepoint_field_list returns a tracepoint field list handle,
 141  * or negative error value.
 142  */
 143 int ustctl_tracepoint_field_list(int sock);
 144
 145 /*
 146  * ustctl_tracepoint_field_list_get is used to iterate on the tp field
 147  * list handle. End is iteration is reached when -LTTNG_UST_ERR_NOENT is
 148  * returned.
 149  */
 150 int ustctl_tracepoint_field_list_get(int sock, int tp_field_list_handle,
 151                 struct lttng_ust_field_iter *iter);
 152
 153 int ustctl_tracer_version(int sock, struct lttng_ust_tracer_version *v);
 154 int ustctl_wait_quiescent(int sock);
 155
 156 int ustctl_sock_flush_buffer(int sock, struct lttng_ust_object_data *object);
 157
 158 int ustctl_calibrate(int sock, struct lttng_ust_calibrate *calibrate);
 159
 160 /* Release object created by members of this API. */
 161 int ustctl_release_object(int sock, struct lttng_ust_object_data *data);
 162 /* Release handle returned by create session. */
 163 int ustctl_release_handle(int sock, int handle);
 164
 165 int ustctl_recv_channel_from_consumer(int sock,
 166                 struct lttng_ust_object_data **channel_data);
 167 int ustctl_recv_stream_from_consumer(int sock,
 168                 struct lttng_ust_object_data **stream_data);
 169 int ustctl_send_channel_to_ust(int sock, int session_handle,
 170                 struct lttng_ust_object_data *channel_data);
 171 int ustctl_send_stream_to_ust(int sock,
 172                 struct lttng_ust_object_data *channel_data,
 173                 struct lttng_ust_object_data *stream_data);
 174
 175 /*
 176  * ustctl_duplicate_ust_object_data allocated a new object in "dest" if
 177  * it succeeds (returns 0). It must be released using
 178  * ustctl_release_object() and then freed with free().
 179  */
 180 int ustctl_duplicate_ust_object_data(struct lttng_ust_object_data **dest,
 181                 struct lttng_ust_object_data *src);
 182
 183 /*
 184  * API used by consumer.
 185  */
 186
 187 struct ustctl_consumer_channel;
 188 struct ustctl_consumer_stream;
 189 struct ustctl_consumer_channel_attr;
 190
 191 int ustctl_get_nr_stream_per_channel(void);
 192
 193 struct ustctl_consumer_channel *
 194         ustctl_create_channel(struct ustctl_consumer_channel_attr *attr,
 195                 const int *stream_fds, int nr_stream_fds);
 196 /*
 197  * Each stream created needs to be destroyed before calling
 198  * ustctl_destroy_channel().
 199  */
 200 void ustctl_destroy_channel(struct ustctl_consumer_channel *chan);
 201
 202 int ustctl_send_channel_to_sessiond(int sock,
 203                 struct ustctl_consumer_channel *channel);
 204 int ustctl_channel_close_wait_fd(struct ustctl_consumer_channel *consumer_chan);
 205 int ustctl_channel_close_wakeup_fd(struct ustctl_consumer_channel *consumer_chan);
 206 int ustctl_channel_get_wait_fd(struct ustctl_consumer_channel *consumer_chan);
 207 int ustctl_channel_get_wakeup_fd(struct ustctl_consumer_channel *consumer_chan);
 208
 209 int ustctl_write_metadata_to_channel(
 210                 struct ustctl_consumer_channel *channel,
 211                 const char *metadata_str,       /* NOT null-terminated */
 212                 size_t len);                    /* metadata length */
 213 ssize_t ustctl_write_one_packet_to_channel(
 214                 struct ustctl_consumer_channel *channel,
 215                 const char *metadata_str,       /* NOT null-terminated */
 216                 size_t len);                    /* metadata length */
 217
 218 /*
 219  * Send a NULL stream to finish iteration over all streams of a given
 220  * channel.
 221  */
 222 int ustctl_send_stream_to_sessiond(int sock,
 223                 struct ustctl_consumer_stream *stream);
 224 int ustctl_stream_close_wait_fd(struct ustctl_consumer_stream *stream);
 225 int ustctl_stream_close_wakeup_fd(struct ustctl_consumer_stream *stream);
 226 int ustctl_stream_get_wait_fd(struct ustctl_consumer_stream *stream);
 227 int ustctl_stream_get_wakeup_fd(struct ustctl_consumer_stream *stream);
 228
 229 /* Create/destroy stream buffers for read */
 230 struct ustctl_consumer_stream *
 231         ustctl_create_stream(struct ustctl_consumer_channel *channel,
 232                         int cpu);
 233 void ustctl_destroy_stream(struct ustctl_consumer_stream *stream);
 234
 235 /* For mmap mode, readable without "get" operation */
 236 int ustctl_get_mmap_len(struct ustctl_consumer_stream *stream,
 237                 unsigned long *len);
 238 int ustctl_get_max_subbuf_size(struct ustctl_consumer_stream *stream,
 239                 unsigned long *len);
 240
 241 /*
 242  * For mmap mode, operate on the current packet (between get/put or
 243  * get_next/put_next).
 244  */
 245 void *ustctl_get_mmap_base(struct ustctl_consumer_stream *stream);
 246 int ustctl_get_mmap_read_offset(struct ustctl_consumer_stream *stream,
 247                 unsigned long *off);
 248 int ustctl_get_subbuf_size(struct ustctl_consumer_stream *stream,
 249                 unsigned long *len);
 250 int ustctl_get_padded_subbuf_size(struct ustctl_consumer_stream *stream,
 251                 unsigned long *len);
 252 int ustctl_get_next_subbuf(struct ustctl_consumer_stream *stream);
 253 int ustctl_put_next_subbuf(struct ustctl_consumer_stream *stream);
 254
 255 /* snapshot */
 256
 257 int ustctl_snapshot(struct ustctl_consumer_stream *stream);
 258 int ustctl_snapshot_sample_positions(struct ustctl_consumer_stream *stream);
 259 int ustctl_snapshot_get_consumed(struct ustctl_consumer_stream *stream,
 260                 unsigned long *pos);
 261 int ustctl_snapshot_get_produced(struct ustctl_consumer_stream *stream,
 262                 unsigned long *pos);
 263 int ustctl_get_subbuf(struct ustctl_consumer_stream *stream,
 264                 unsigned long *pos);
 265 int ustctl_put_subbuf(struct ustctl_consumer_stream *stream);
 266
 267 void ustctl_flush_buffer(struct ustctl_consumer_stream *stream,
 268                 int producer_active);
 269 void ustctl_clear_buffer(struct ustctl_consumer_stream *stream);
 270
 271 /* index */
 272
 273 /*
 274  * Getters which need to be used on the current packet (between get/put
 275  * or get_next/put_next.
 276  */
 277
 278 int ustctl_get_timestamp_begin(struct ustctl_consumer_stream *stream,
 279                 uint64_t *timestamp_begin);
 280 int ustctl_get_timestamp_end(struct ustctl_consumer_stream *stream,
 281         uint64_t *timestamp_end);
 282 int ustctl_get_events_discarded(struct ustctl_consumer_stream *stream,
 283         uint64_t *events_discarded);
 284 int ustctl_get_content_size(struct ustctl_consumer_stream *stream,
 285         uint64_t *content_size);
 286 int ustctl_get_packet_size(struct ustctl_consumer_stream *stream,
 287         uint64_t *packet_size);
 288 int ustctl_get_sequence_number(struct ustctl_consumer_stream *stream,
 289                 uint64_t *seq);
 290
 291 /*
 292  * Getter returning state invariant for the stream, which can be used
 293  * without "get" operation.
 294  */
 295
 296 int ustctl_get_stream_id(struct ustctl_consumer_stream *stream,
 297                 uint64_t *stream_id);
 298 int ustctl_get_instance_id(struct ustctl_consumer_stream *stream,
 299                 uint64_t *id);
 300
 301 /*
 302  * Getter returning the current timestamp as perceived from the
 303  * tracer.
 304  */
 305 int ustctl_get_current_timestamp(struct ustctl_consumer_stream *stream,
 306                 uint64_t *ts);
 307
 308 /* returns whether UST has perf counters support. */
 309 int ustctl_has_perf_counters(void);
 310
 311 /* Regenerate the statedump. */
 312 int ustctl_regenerate_statedump(int sock, int handle);
 313
 314 /* event registry management */
 315
 316 enum ustctl_socket_type {
 317         USTCTL_SOCKET_CMD = 0,
 318         USTCTL_SOCKET_NOTIFY = 1,
 319 };
 320
 321 enum ustctl_notify_cmd {
 322         USTCTL_NOTIFY_CMD_EVENT = 0,
 323         USTCTL_NOTIFY_CMD_CHANNEL = 1,
 324         USTCTL_NOTIFY_CMD_ENUM = 2,
 325 };
 326
 327 enum ustctl_channel_header {
 328         USTCTL_CHANNEL_HEADER_UNKNOWN = 0,
 329         USTCTL_CHANNEL_HEADER_COMPACT = 1,
 330         USTCTL_CHANNEL_HEADER_LARGE = 2,
 331 };
 332
 333 /* event type structures */
 334
 335 enum ustctl_abstract_types {
 336         ustctl_atype_integer,
 337         ustctl_atype_enum,      /* legacy */
 338         ustctl_atype_array,     /* legacy */
 339         ustctl_atype_sequence,  /* legacy */
 340         ustctl_atype_string,
 341         ustctl_atype_float,
 342         ustctl_atype_variant,   /* legacy */
 343         ustctl_atype_struct,    /* legacy */
 344         ustctl_atype_enum_nestable,
 345         ustctl_atype_array_nestable,
 346         ustctl_atype_sequence_nestable,
 347         ustctl_atype_struct_nestable,
 348         ustctl_atype_variant_nestable,
 349         NR_USTCTL_ABSTRACT_TYPES,
 350 };
 351
 352 enum ustctl_string_encodings {
 353         ustctl_encode_none = 0,
 354         ustctl_encode_UTF8 = 1,
 355         ustctl_encode_ASCII = 2,
 356         NR_USTCTL_STRING_ENCODINGS,
 357 };
 358
 359 #define USTCTL_UST_INTEGER_TYPE_PADDING 24
 360 struct ustctl_integer_type {
 361         uint32_t size;          /* in bits */
 362         uint32_t signedness;
 363         uint32_t reverse_byte_order;
 364         uint32_t base;          /* 2, 8, 10, 16, for pretty print */
 365         int32_t encoding;       /* enum ustctl_string_encodings */
 366         uint16_t alignment;     /* in bits */
 367         char padding[USTCTL_UST_INTEGER_TYPE_PADDING];
 368 } LTTNG_PACKED;
 369
 370 #define USTCTL_UST_FLOAT_TYPE_PADDING   24
 371 struct ustctl_float_type {
 372         uint32_t exp_dig;               /* exponent digits, in bits */
 373         uint32_t mant_dig;              /* mantissa digits, in bits */
 374         uint32_t reverse_byte_order;
 375         uint16_t alignment;     /* in bits */
 376         char padding[USTCTL_UST_FLOAT_TYPE_PADDING];
 377 } LTTNG_PACKED;
 378
 379 #define USTCTL_UST_ENUM_VALUE_PADDING   15
 380 struct ustctl_enum_value {
 381         uint64_t value;
 382         uint8_t signedness;
 383         char padding[USTCTL_UST_ENUM_VALUE_PADDING];
 384 } LTTNG_PACKED;
 385
 386 enum ustctl_ust_enum_entry_options {
 387         USTCTL_UST_ENUM_ENTRY_OPTION_IS_AUTO = 1U << 0,
 388 };
 389
 390 #define USTCTL_UST_ENUM_ENTRY_PADDING   32
 391 struct ustctl_enum_entry {
 392         struct ustctl_enum_value start, end; /* start and end are inclusive */
 393         char string[LTTNG_UST_SYM_NAME_LEN];
 394         union {
 395                 struct {
 396                         uint32_t options;
 397                 } LTTNG_PACKED extra;
 398                 char padding[USTCTL_UST_ENUM_ENTRY_PADDING];
 399         } u;
 400 } LTTNG_PACKED;
 401
 402 /* legacy */
 403 #define USTCTL_UST_BASIC_TYPE_PADDING   296
 404 union _ustctl_basic_type {
 405         struct ustctl_integer_type integer;
 406         struct {
 407                 char name[LTTNG_UST_SYM_NAME_LEN];
 408                 struct ustctl_integer_type container_type;
 409                 uint64_t id;    /* enum ID in sessiond. */
 410         } enumeration;
 411         struct {
 412                 int32_t encoding;       /* enum ustctl_string_encodings */
 413         } string;
 414         struct ustctl_float_type _float;
 415         char padding[USTCTL_UST_BASIC_TYPE_PADDING];
 416 } LTTNG_PACKED;
 417
 418 /* legacy */
 419 struct ustctl_basic_type {
 420         enum ustctl_abstract_types atype;
 421         union {
 422                 union _ustctl_basic_type basic;
 423         } u;
 424 } LTTNG_PACKED;
 425
 426 /*
 427  * Padding is derived from largest member: u.legacy.sequence which
 428  * contains two basic types, each with USTCTL_UST_BASIC_TYPE_PADDING.
 429  */
 430 #define USTCTL_UST_TYPE_PADDING (2 * USTCTL_UST_BASIC_TYPE_PADDING)
 431 struct ustctl_type {
 432         enum ustctl_abstract_types atype;
 433         union {
 434                 struct ustctl_integer_type integer;
 435                 struct ustctl_float_type _float;
 436                 struct {
 437                         int32_t encoding;       /* enum ustctl_string_encodings */
 438                 } string;
 439                 struct {
 440                         char name[LTTNG_UST_SYM_NAME_LEN];
 441                         uint64_t id;    /* enum ID in sessiond. */
 442                         /* container_type follows after this struct ustctl_field. */
 443                 } enum_nestable;
 444                 struct {
 445                         uint32_t length;                /* num. elems. */
 446                         uint32_t alignment;
 447                         /* elem_type follows after this struct ustctl_field. */
 448                 } array_nestable;
 449                 struct {
 450                         char length_name[LTTNG_UST_SYM_NAME_LEN];
 451                         uint32_t alignment;             /* Alignment before elements. */
 452                         /* elem_type follows after the length_type. */
 453                 } sequence_nestable;
 454                 struct {
 455                         uint32_t nr_fields;
 456                         uint32_t alignment;
 457                         /* Followed by nr_fields struct ustctl_field. */
 458                 } struct_nestable;
 459                 struct {
 460                         uint32_t nr_choices;
 461                         char tag_name[LTTNG_UST_SYM_NAME_LEN];
 462                         uint32_t alignment;
 463                         /* Followed by nr_choices struct ustctl_field. */
 464                 } variant_nestable;
 465
 466                 /* Legacy ABI */
 467                 union {
 468                         union _ustctl_basic_type basic;
 469                         struct {
 470                                 struct ustctl_basic_type elem_type;
 471                                 uint32_t length;                /* num. elems. */
 472                         } array;
 473                         struct {
 474                                 struct ustctl_basic_type length_type;
 475                                 struct ustctl_basic_type elem_type;
 476                         } sequence;
 477                         struct {
 478                                 uint32_t nr_fields;
 479                                 /* Followed by nr_fields struct ustctl_field. */
 480                         } _struct;
 481                         struct {
 482                                 uint32_t nr_choices;
 483                                 char tag_name[LTTNG_UST_SYM_NAME_LEN];
 484                                 /* Followed by nr_choices struct ustctl_field. */
 485                         } variant;
 486                 } legacy;
 487                 char padding[USTCTL_UST_TYPE_PADDING];
 488         } u;
 489 } LTTNG_PACKED;
 490
 491 #define USTCTL_UST_FIELD_PADDING        28
 492 struct ustctl_field {
 493         char name[LTTNG_UST_SYM_NAME_LEN];
 494         struct ustctl_type type;
 495         char padding[USTCTL_UST_FIELD_PADDING];
 496 } LTTNG_PACKED;
 497
 498 /*
 499  * Returns 0 on success, negative error value on error.
 500  * If an error other than -LTTNG_UST_ERR_UNSUP_MAJOR is returned,
 501  * the output fields are not populated.
 502  */
 503 int ustctl_recv_reg_msg(int sock,
 504         enum ustctl_socket_type *type,
 505         uint32_t *major,
 506         uint32_t *minor,
 507         uint32_t *pid,
 508         uint32_t *ppid,
 509         uint32_t *uid,
 510         uint32_t *gid,
 511         uint32_t *bits_per_long,
 512         uint32_t *uint8_t_alignment,
 513         uint32_t *uint16_t_alignment,
 514         uint32_t *uint32_t_alignment,
 515         uint32_t *uint64_t_alignment,
 516         uint32_t *long_alignment,
 517         int *byte_order,
 518         char *name);    /* size LTTNG_UST_ABI_PROCNAME_LEN */
 519
 520 /*
 521  * Returns 0 on success, negative UST or system error value on error.
 522  * Receive the notification command. The "notify_cmd" can then be used
 523  * by the caller to find out which ustctl_recv_* function should be
 524  * called to receive the notification, and which ustctl_reply_* is
 525  * appropriate.
 526  */
 527 int ustctl_recv_notify(int sock, enum ustctl_notify_cmd *notify_cmd);
 528
 529 /*
 530  * Returns 0 on success, negative UST or system error value on error.
 531  */
 532 int ustctl_recv_register_event(int sock,
 533         int *session_objd,              /* session descriptor (output) */
 534         int *channel_objd,              /* channel descriptor (output) */
 535         char *event_name,               /*
 536                                          * event name (output,
 537                                          * size LTTNG_UST_SYM_NAME_LEN)
 538                                          */
 539         int *loglevel,
 540         char **signature,               /*
 541                                          * event signature
 542                                          * (output, dynamically
 543                                          * allocated, must be free(3)'d
 544                                          * by the caller if function
 545                                          * returns success.)
 546                                          */
 547         size_t *nr_fields,
 548         struct ustctl_field **fields,
 549         char **model_emf_uri);
 550
 551 /*
 552  * Returns 0 on success, negative error value on error.
 553  */
 554 int ustctl_reply_register_event(int sock,
 555         uint32_t id,                    /* event id (input) */
 556         int ret_code);                  /* return code. 0 ok, negative error */
 557
 558 /*
 559  * Returns 0 on success, negative UST or system error value on error.
 560  */
 561 int ustctl_recv_register_enum(int sock,
 562         int *session_objd,
 563         char *enum_name,
 564         struct ustctl_enum_entry **entries,
 565         size_t *nr_entries);
 566
 567 /*
 568  * Returns 0 on success, negative error value on error.
 569  */
 570 int ustctl_reply_register_enum(int sock,
 571         uint64_t id,                    /* enum id (input) */
 572         int ret_code);
 573
 574 /*
 575  * Returns 0 on success, negative UST or system error value on error.
 576  */
 577 int ustctl_recv_register_channel(int sock,
 578         int *session_objd,              /* session descriptor (output) */
 579         int *channel_objd,              /* channel descriptor (output) */
 580         size_t *nr_fields,              /* context fields */
 581         struct ustctl_field **fields);
 582
 583 /*
 584  * Returns 0 on success, negative error value on error.
 585  */
 586 int ustctl_reply_register_channel(int sock,
 587         uint32_t chan_id,
 588         enum ustctl_channel_header header_type,
 589         int ret_code);                  /* return code. 0 ok, negative error */
 590
 591 #endif /* _LTTNG_UST_CTL_H */