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   5 .Dd July  9, 2018
   6 .Dt IEC61883 7I
   7 .Os
   8 .Sh NAME
   9 .Nm iec61883
  10 .Nd IEC 61883 interfaces
  11 .Sh SYNOPSIS
  12 .In sys/av/iec61883.h
  13 .Sh DESCRIPTION
  14 The set of interfaces described in this man page can be used to control and
  15 exchange data with consumer audio/video devices using protocols specified
  16 in
  17 .%T "IIEC 61883 Consumer Electronic Audio/Video Equipment - Digital Interface"
  18 including Common Isochronous Packet (CIP), Connection Management
  19 Procedures (CMP) and Function Control Protocol (FCP).
  20 .Pp
  21 An
  22 .Nm
  23 compliant driver exports two device nodes for isochronous and
  24 for asynchronous transactions.
  25 See the
  26 .Sx FILES
  27 section of this man page for the namespace definition.
  28 .Ss "Isochronous Transfers"
  29 Two methods are provided to receive/transmit isochronous data: using
  30 .Xr mmap 2
  31 in combination with
  32 .Xr ioctl 2 ,
  33 and
  34 .Xr read 2
  35 or
  36 .Xr write 2 .
  37 .Ss "Mmap/Ioctl"
  38 This method provides better performance and finer-grained control than
  39 read/write, and is a method of choice for most applications.
  40 The data buffer is
  41 mapped into a user process address space, which means no data copying between
  42 the kernel and an application is necessary.
  43 Synchronization between user
  44 processes and the driver is performed using
  45 .Xr ioctl 2
  46 commands.
  47 .Pp
  48 An application allocates resources for isochronous transfer using
  49 .Dv IEC61883_ISOCH_INIT .
  50 Then the data buffer can be mapped into the process
  51 space using
  52 .Xr mmap 2 .
  53 .Pp
  54 A circular data buffer consists of one or more equal size frame buffers
  55 (further referred to as frames, unless to avoid ambiguity with AV frames).
  56 Frames are numbered starting with zero and are always transferred sequentially.
  57 Frames consist equal sized packets.
  58 Each packet contains a CIP header and one or more data blocks.
  59 .Pp
  60 A driver and an application act as a producer and a consumer: producer supplies
  61 .Em full
  62 frames (filled with data) to the consumer, and the producer is not
  63 allowed to access those frames until the consumer claims them
  64 .Em empty .
  65 .Pp
  66 A transfer can be initiated and suspended with
  67 .Dv IEC61883_START
  68 and
  69 .Dv IEC61883_STOP
  70 commands respectively.
  71 .Dv IEC61883_RECV
  72 or
  73 .Dv IEC61883_XMIT
  74 is used for producer-consumer synchronization.
  75 .Ss "Read/Write"
  76 Using this method, an application calls
  77 .Xr read 2
  78 or
  79 .Xr write 2
  80 to receive or transmit a specified amount of data.
  81 Bus-specific overhead, such as isochronous packet headers, is handled by the driver
  82 and is not exposed to applications.
  83 Data returned by
  84 .Xr read 2
  85 contains CIP headers and data blocks.
  86 Empty packets are not returned by
  87 .Xr read 2 .
  88 .Xr write 2
  89 data should meet the same requirements.
  90 .Pp
  91 If one or more channels have been allocated since
  92 .Xr open 2
  93 (see
  94 .Dv IEC61883_ISOCH_INIT ) ,
  95 the data is received/transmitted using channel that was created the last.
  96 .Pp
  97 If no channels were allocated, the driver uses the broadcast channel by default
  98 and allocates the default-size data buffer.
  99 During transmit, the first packet's CIP header is used to auto-detect the data format.
 100 If it is one of the formats supported by the driver, it is properly transmitted (with
 101 inserted empty packets and timestamps).
 102 .Pp
 103 For both methods, if during transmit the driver runs out of data, it transmits
 104 empty packets containing only a CIP header of the next to be transmitted
 105 packet, as defined in
 106 .Em IEC 61883-1 .
 107 .Ss "Connection Management Procedures"
 108 Applications wishing to follow Connection Management Procedures (CMP) in
 109 combination with isochronous transfers should use the
 110 .Xr ioctl 2
 111 .Dv IEC61883_PLUG_INIT ,
 112 .Dv IEC61883_PLUG_FINI ,
 113 .Dv IEC61883_PLUG_REG_READ
 114 and
 115 .Dv IEC61883_PLUG_REG_CAS
 116 commands.
 117 .Ss "Asynchronous Transactions"
 118 .Xr read 2 ,
 119 .Xr write 2 ,
 120 .Xr ioctl 2 ,
 121 and
 122 .Xr poll 2
 123 can be used
 124 with asynchronous nodes.
 125 Asynchronous data exchange between a driver and an
 126 application utilizes a common data structure called asynchronous request (ARQ):
 127 .Bd -literal -offset 2n
 128 typedef struct iec61883_arq {
 129         int        arq_type;
 130         int        arq_len;
 131         union {
 132                 uint32_t   quadlet;
 133                 uint64_t   octlet;
 134                 uint8_t    buf[8];
 135         } arq_data;
 136 } iec61883_arq_t;
 137 .Ed
 138 .Pp
 139 .Fa arq_type
 140 contains
 141 .Sy ARQ
 142 type:
 143 .Pp
 144 .Bl -tag -width " " -compact
 145 .It Dv IEC61883_ARQ_FCP_CMD
 146 .It Dv IEC61883_ARQ_FCP_RESP
 147 .Pp
 148 .Sy FCP
 149 command and response frame respectively.
 150 Outgoing frames are sent using
 151 .Xr write 2 ,
 152 incoming frames are received with
 153 .Xr read 2 .
 154 .Pp
 155 See
 156 .Em IIEC 61883-1
 157 for the FCP frame structure definition.
 158 .Pp
 159 .It Dv IEC61883_ARQ_BUS_RESET
 160 .Pp
 161 Returned by the driver when a bus reset occurs.
 162 There is no data associated with this request type, and \fBarq_len\fR is set to 0.
 163 .El
 164 .Pp
 165 If
 166 .Fa arq_len
 167 is 4 or 8, then data should be supplied in
 168 .Fa arq_data.quadlet
 169 or
 170 .Fa arq_data.octlet
 171 respectively, otherwise up to 8 bytes can be put in
 172 .Fa arq_data.buf ,
 173 with the rest of the data following immediately after.
 174 .Ss "write(2)"
 175 For a request to be sent to a target, an
 176 .Vt iec61883_arq_t
 177 structure along with associated data is passed to the driver using
 178 .Xr write 2 .
 179 .Xr write 2
 180 blocks until the request is completed.
 181 .Ss "read(2)"
 182 A driver collects incoming ARQs in the internal buffer.
 183 Buffer size can be changed using the
 184 .Xr ioctl 2
 185 command
 186 .Vt IEC61883_FCP_SET_IBUF_SIZE .
 187 .Pp
 188 Reading an ARQ takes one or two steps depending on data length.
 189 An application
 190 first reads
 191 .Ql sizeof (iec61883_arq_t)
 192 bytes: if
 193 .Fa arq_len
 194 is less than or equal 4, which is usually the case, no additional step is needed.
 195 Otherwise,
 196 the remaining
 197 .Ql arq_len - 4
 198 bytes should be read and concatenated.
 199 .Pp
 200 .Xr read 2
 201 blocks until the specified amount of data is available, unless
 202 .Dv O_NONBLOCK
 203 or
 204 .Dv O_NDELAY
 205 flag was set during
 206 .Xr open 2 ,
 207 in which case
 208 .Xr read 2
 209 returns immediately.
 210 .Ss "poll(2)"
 211 Applications can
 212 .Xr poll 2
 213 asynchronous nodes on the
 214 .Dv POLLIN
 215 event.
 216 .Ss "Bus Reset"
 217 In case of a bus reset, the driver notifies an application by generating an
 218 .Sy ARQ
 219 of type
 220 .Dv IEC61883_ARQ_BUS_RESET .
 221 .Pp
 222 If there were established isochronous connections before bus reset, the driver
 223 attempts to restore all connections as described in
 224 .Em IEC 61883
 225 and resume any active transfers that were in progress.
 226 .Sh IOCTLS
 227 The following commands only apply to isochronous nodes:
 228 .Bl -tag -width " "
 229 .It Dv IEC61883_ISOCH_INIT
 230 .Pp
 231 This command allocates a data buffer and isochronous resources (if necessary)
 232 for the isochronous transfer.
 233 The argument is a pointer to the structure:
 234 .Bd -literal -offset 2n
 235 typedef struct iec61883_isoch_init {
 236       int   ii_version;     /* interface version */
 237       int   ii_pkt_size;    /* packet size */
 238       int   ii_frame_size;  /* packets/frame */
 239       int   ii_frame_cnt;   /* # of frames */
 240       int   ii_direction;   /* xfer direction */
 241       int   ii_bus_speed;   /* bus speed */
 242       uint64_t ii_channel;  /* channel mask */
 243       int   ii_dbs;         /* DBS */
 244       int   ii_fn;          /* FN */
 245       int   ii_rate_n;      /* rate numerator */
 246       int   ii_rate_d;      /* rate denominator */
 247       int   ii_ts_mode;     /* timestamp mode */
 248       int   ii_flags;       /* flags */
 249       int   ii_handle;      /* isoch handle */
 250       int   ii_frame_rcnt;  /* # of frames */
 251       off_t *ii_mmap_off    /* mmap offset */
 252       int   ii_rchannel;    /* channel */
 253       int   ii_error;       /* error code */
 254 } iec61883_isoch_init_t;
 255 .Ed
 256 .Pp
 257 .Fa ii_version
 258 should be set to
 259 .Dv IEC61883_V1_0 .
 260 .Pp
 261 The driver attempts to allocate a data buffer consisting of
 262 .Fa ii_frame_cnt
 263 frames, with
 264 .Fa ii_frame_size
 265 packets in each frame.
 266 Packet size in bytes is specified by
 267 .Fa ii_pkt_size
 268 specifies and should be a multiple of 512 and compatible with
 269 .Fa ii_bus_speed .
 270 .Pp
 271 .Fa ii_direction
 272 can take one of the following values:
 273 .Bl -tag -width "IEC61883_DIR_RECV"
 274 .It Dv IEC61883_DIR_RECV
 275 Receiving isochronous data.
 276 .It Dv IEC61883_DIR_XMIT
 277 Transmitting isochronous data.
 278 .El
 279 .Pp
 280 .Fa ii_bus_speed
 281 chooses bus speed to be used and can be either
 282 .Dv IEC61883_S100 ,
 283 .Dv IEC61883_S200
 284 or
 285 .Dv IEC61883_S400 .
 286 .Pp
 287 .Fa ii_channel
 288 is a mask that specifies an isochronous channel number to be
 289 used, with the
 290 .Em N Ns th
 291 bit representing channel
 292 .Em N .
 293 When transmitting data, several bits can be set at a time, in which case the
 294 driver chooses one, for example,
 295 .Sy 0x3FF
 296 means a range from 0 to 9.
 297 In case of receive, only one bit can be set.
 298 .Pp
 299 .Fa ii_dbs
 300 specifies data block size in quadlets, for example, DBS value for
 301 .Dv SD-DVCR
 302 is
 303 .Sy 0x78 .
 304 Refer to
 305 .Em IEC 61883
 306 for more details on DBS.
 307 .Pp
 308 .Fa ii_fn
 309 specifies fraction number, which defines the number of blocks in which a
 310 source packet is divided.
 311 Allowed values are from 0 to 3.
 312 Refer to
 313 .Em IEC 61883
 314 for more details on FN.
 315 .Pp
 316 Data rate expected by the AV device can be lower than the bus speed, in which
 317 case the driver has to periodically insert empty packets into the data stream
 318 to avoid device buffer overflows.
 319 This rate is specified with a fraction N/D,
 320 set by
 321 .Fa ii_rate_n
 322 and
 323 .Fa ii_rate_d
 324 respectively.
 325 Any integer numbers can be used, or the following predefined constants:
 326 .Pp
 327 .Bl -tag -width "IEC61883_RATE_N_DV_NTSC" -compact
 328 .It Dv IEC61883_RATE_N_DV_NTSC
 329 .It Dv IEC61883_RATE_D_DV_NTSC
 330 Data rate expected by
 331 .Sy DV-NTSC
 332 devices.
 333 .Pp
 334 .It Dv IEC61883_RATE_N_DV_PAL
 335 .It Dv IEC61883_RATE_D_DV_PAL
 336 Data rate expected by
 337 .Sy DV-PAL
 338 devices.
 339 .El
 340 .Pp
 341 During data transmission, a timestamp based on the current value of the cycle
 342 timer is usually required.
 343 .Fa ii_ts_mode
 344 defines timestamp mode to be used:
 345 .Bl -tag -width IEC61883_TS_NONE
 346 .It Dv IEC61883_TS_SYT
 347 Driver puts a timestamp in the SYT field of the first CIP header of each frame.
 348 .It Dv IEC61883_TS_NONE
 349 No timestamps.
 350 .El
 351 .Pp
 352 .Fa ii_dbs ,
 353 .Fa ii_fn ,
 354 .Fa ii_rate_n ,
 355 .Fa ii_rate_d
 356 and
 357 .Fa ii_ts_mode
 358 are only required for transmission.
 359 In other case these should be set to 0.
 360 .Pp
 361 .Fa ii_flags
 362 should be set to 0.
 363 .Pp
 364 If command succeeds,
 365 .Fa ii_handle
 366 contains a handle that should be used with other isochronous commands.
 367 .Fa ii_frame_rcnt
 368 contains the number of allocated frames (can be less than
 369 .Fa ii_frame_cnt ) .
 370 .Fa ii_mmap_off
 371 contains an offset to be used in
 372 .Xr mmap 2 ,
 373 for example, to map an entire data receive buffer:
 374 .Bd -literal -offset 2n
 375 pa = mmap(NULL, init.ii_pkt_size *
 376       init.ii_frame_size * init.ii_frame_rcnt,
 377       PROT_READ, MAP_PRIVATE, fd, init.ii_mmap_off);
 378 .Ed
 379 .Pp
 380 .Fa ii_rchannel
 381 contains channel number.
 382 .Pp
 383 In case of command success,
 384 .Fa ii_error
 385 is set to 0; otherwise one of the following values can be returned:
 386 .Bl -tag -width IEC61883_ERR_NOCHANNEL
 387 .It Dv IEC61883_ERR_NOMEM
 388 Not enough memory for the data buffer.
 389 .It Dv IEC61883_ERR_NOCHANNEL
 390 Cannot allocate isochronous channel.
 391 .It Dv IEC61883_ERR_PKT_SIZE
 392 Packet size is not allowed at this bus speed.
 393 .It Dv IEC61883_ERR_VERSION
 394 Interface version is not supported.
 395 .It Dv IEC61883_ERR_INVAL
 396 One or more the parameters are invalid
 397 .It Dv IEC61883_ERR_OTHER
 398 Unspecified error type.
 399 .El
 400 .It Dv IEC61883_ISOCH_FINI
 401 .Pp
 402 Argument is a handle returned by
 403 .Dv IEC61883_ISOCH_INIT .
 404 This command frees any resources associated with this handle.
 405 There must be no active transfers
 406 and the data buffer must be unmapped; otherwise the command fails.
 407 .It Dv IEC61883_START
 408 .Pp
 409 This command starts an isochronous transfer.
 410 The argument is a handle returned
 411 by
 412 .Dv IEC61883_ISOCH_INIT .
 413 .It Dv IEC61883_STOP
 414 .Pp
 415 This command stops an isochronous transfer.
 416 The argument is a handle returned by
 417 .Dv IEC61883_ISOCH_INIT .
 418 .It Dv IEC61883_RECV
 419 .Pp
 420 This command is used to receive full frames and return empty frames to the driver.
 421 The argument is a pointer to the structure:
 422 .Bd -literal -offset 2n
 423 typedef struct iec61883_recv {
 424         int   rx_handle;    /* isoch handle */
 425         int   rx_flags;     /* flags */
 426         iec61883_xfer_t rx_xfer;   /* xfer params */
 427 } iec61883_recv_t;
 428 
 429 typedef struct iec61883_xfer {
 430         int   xf_empty_idx; /* first empty frame */
 431         int   xf_empty_cnt; /* empty frame count */
 432         int   xf_full_idx;  /* first full frame */
 433         int   xf_full_cnt;  /* full frame count */
 434         int   xf_error;     /* error */
 435 } iec61883_xfer_t;
 436 .Ed
 437 .Pp
 438 .Fa rx_flags
 439 should be set to 0.
 440 .Pp
 441 An application sets
 442 .Fa xf_empty_idx
 443 and
 444 .Fa xf_empty_cnt
 445 to indicate frames it no longer needs.
 446 E. g.  if a buffer consists of 6 frames,
 447 .Fa xf_empty_idx
 448 is 4,
 449 .Fa xf_empty_cnt
 450 is 3 - means that frames 4, 5 and 0 can now be reused by the driver.
 451 If there are no empty frames, for example, the
 452 first time this command is called,
 453 .Fa xf_empty_cnt
 454 should be set to 0.
 455 .Pp
 456 When the command returns,
 457 .Fa xf_full_idx
 458 and
 459 .Fa xf_full_cnt
 460 specifies the frames that are full.
 461 .Fa xf_error
 462 is always 0.
 463 .Pp
 464 In general, AV frame boundaries are not aligned with the frame buffer
 465 boundaries, because the first received packet might not be the first packet of
 466 an AV frame, and, in contrast with the read/write method, the driver does not
 467 remove empty CIP packets.
 468 .Pp
 469 Applications should detect empty packets by comparing adjacent packets'
 470 continuity counters (DBC field of the CIP header).
 471 .It Dv IEC61883_XMIT
 472 .Pp
 473 This command is used to transmit full frames and get more empty frames from the
 474 driver.
 475 The argument is a pointer to the structure:
 476 .Bd -literal -offset 2n
 477 typedef struct iec61883_xmit {
 478         int   tx_handle;         /* isoch handle */
 479         int   tx_flags;          /* flags */
 480         iec61883_xfer_t tx_xfer; /* xfer params */
 481         int   tx_miss_cnt;       /* missed cycles */
 482  } iec61883_xmit_t;
 483 .Ed
 484 .Pp
 485 .Fa tx_flags
 486 should be set to zero.
 487 .Pp
 488 The application sets
 489 .Fa xf_full_idx
 490 and
 491 .Fa xf_full_cnt
 492 to specify frames it wishes to transmit.
 493 If there are no frames to transmit (e. g. the first time this command is called),
 494 .Fa xf_full_cnt
 495 should be set to 0.
 496 .Pp
 497 When the command returns,
 498 .Fa xf_empty_idx
 499 and
 500 .Fa xf_empty_cnt
 501 specifies empty frames which can be to transmit more data.
 502 .Fa xf_error
 503 is always 0.
 504 .Pp
 505 .Fa tx_miss_cnt
 506 contains the number of isochronous cycles missed since last
 507 transfer due to data buffer under run.
 508 This can happen when an application does not supply data fast enough.
 509 For the purposes of time stamping, the driver considers the first packet in a
 510 frame buffer to be the first packet of an AV frame.
 511 .It Dv IEC61883_PLUG_INIT
 512 .Pp
 513 This command returns a handle for the specified plug.
 514 The argument is a pointer
 515 to the structure:
 516 .Bd -literal -offset 2n
 517 typedef struct iec61883_plug_init {
 518         int   pi_ver;     /* interface version */
 519         int   pi_loc;     /* plug location */
 520         int   pi_type;    /* plug type */
 521         int   pi_num;     /* plug number */
 522         int   pi_flags;   /* flags */
 523         int   pi_handle;  /* plug handle */
 524         int   pi_rnum;    /* plug number */
 525  } iec61883_plug_init_t;
 526 .Ed
 527 .Pp
 528 .Fa pi_ver
 529 should be set to
 530 .Dv IEC61883_V1_0 .
 531 .Pp
 532 .Fa pi_loc
 533 specifies plug location:
 534 .Bl -tag -width IEC61883_LOC_REMOTE
 535 .It Dv IEC61883_LOC_LOCAL
 536 On the local unit (local plug).
 537 A plug control register (PCR) is allocated.
 538 Command fails if the plug already exists
 539 .It Dv IEC61883_LOC_REMOTE
 540 On the remote unit (remote plug).
 541 The plug should exist on the remote unit,
 542 otherwise the command fails.
 543 .El
 544 .Pp
 545 .Fa pi_type
 546 specifies isochronous plug type:
 547 .Pp
 548 .Bl -tag -width " " -compact
 549 .It Dv IEC61883_PLUG_IN
 550 .It Dv IEC61883_PLUG_OUT
 551 .Pp
 552 Input or output plugs.
 553 .Pp
 554 .It Dv IEC61883_PLUG_MASTER_IN
 555 .It Dv IEC61883_PLUG_MASTER_OUT
 556 .Pp
 557 Master input or master output plug.
 558 These plugs always exist on the local unit.
 559 .El
 560 .Pp
 561 .Fa pi_num
 562 specifies plug number.
 563 This should be 0 for master plugs, and from 0 to 31 for input/output plugs.
 564 Alternatively, a special value
 565 .Dv IEC61883_PLUG_ANY
 566 can be used to let the driver choose a free plug
 567 number, create the plug and return the number in
 568 .Fa pi_rnum .
 569 .Pp
 570 .Fa pi_flags
 571 should be set to 0.
 572 .Pp
 573 If the command succeeds,
 574 .Fa pi_handle
 575 contains a handle that should be used with other plug commands.
 576 .It Dv IEC61883_PLUG_FINI
 577 .Pp
 578 Argument is a handle returned by
 579 .Dv IEC61883_PLUG_INIT .
 580 This command frees any resources associated with this handle, including the PCR.
 581 .It Dv IEC61883_PLUG_REG_READ
 582 .Pp
 583 Read plug register value.
 584 The argument is a pointer to the structure:
 585 .Bd -literal -offset 2n
 586 typedef struct iec61883_plug_reg_val {
 587         int         pr_handle; /* plug handle */
 588         uint32_t    pr_val;    /* register value */
 589 } iec61883_plug_reg_val_t;
 590 .Ed
 591 .Pp
 592 .Fa pr_handle
 593 is a handle returned by
 594 .Dv IEC61883_PLUG_INIT .
 595 Register
 596 value is returned in
 597 .Fa pr_val .
 598 .It Dv IEC61883_PLUG_REG_CAS
 599 .Pp
 600 Atomically compare and swap plug register value.
 601 The argument is a pointer to the structure:
 602 .Bd -literal -offset 2n
 603 typedef struct iec61883_plug_reg_lock {
 604         int        pl_handle; /* plug handle */
 605         uint32_t   pl_arg;    /* compare arg */
 606         uint32_t   pl_data;   /* write value */
 607         UINT32_t   pl_old;    /* original value */
 608 } iec61883_plug_reg_lock_t;
 609 .Ed
 610 .Pp
 611 .Fa pr_handle
 612 is a handle returned by IEC61883_PLUG_INIT.
 613 .Pp
 614 Original register value is compared with
 615 .Fa pl_arg
 616 and if they are equal, register value is replaced with
 617 .Fa pl_data .
 618 In any case, the original value is stored in
 619 .Fa pl_old .
 620 .El
 621 .Pp
 622 The following commands only apply to asynchronous nodes:
 623 .Bl -tag -width " "
 624 .It Dv IEC61883_ARQ_GET_IBUF_SIZE
 625 .Pp
 626 This command returns current incoming ARQ buffer size.
 627 The argument is a
 628 pointer to
 629 .Vt int .
 630 .It Dv IEC61883_ARQ_SET_IBUF_SIZE
 631 .Pp
 632 This command changes incoming ARQ buffer size.
 633 The argument is the new buffer
 634 size in bytes.
 635 .El
 636 .Sh FILES
 637 .Bl -tag -width /dev/av/N/async
 638 .It Pa /dev/av/N/async
 639 Device node for asynchronous data
 640 .It Pa /dev/av/N/isoch
 641 Device has been disconnected
 642 .El
 643 .Sh ERRORS
 644 .Bl -tag -width EFAULT
 645 .It Er EIO
 646 Bus operation failed.
 647 DMA failure.
 648 .It Er EFAULT
 649 .Xr ioctl 2
 650 argument points to an illegal address.
 651 .It Er EINVAL
 652 Invalid argument or argument combination.
 653 .It Er ENODEV
 654 Device has been disconnected.
 655 .El
 656 .Sh ARCHITECTURE
 657 All
 658 .Sh INTERFACE STABILITY
 659 Committed
 660 .Sh SEE ALSO
 661 .Xr ioctl 2 ,
 662 .Xr mmap 2 ,
 663 .Xr open 2 ,
 664 .Xr poll 2 ,
 665 .Xr read 2 ,
 666 .Xr write 2 ,
 667 .Xr attributes 5 ,
 668 .Xr av1394 7D
 669 .Rs
 670 .%B IIEC 61883 Consumer audio/video equipment - Digital interface
 671 .Re
 672 .Rs
 673 .%B IEEE Std 1394-1995 Standard for a High Performance Serial Bus
 674 .Re