Tribblix: manual page: iec61883.4i

IEC61883(4I) Ioctl Requests IEC61883(4I)

NAME

iec61883 - IEC 61883 interfaces

SYNOPSIS

#include <sys/av/iec61883.h>

DESCRIPTION

The set of interfaces described in this man page can be used to control
and exchange data with consumer audio/video devices using protocols
specified in IIEC 61883 Consumer Electronic Audio/Video Equipment -
Digital Interface including Common Isochronous Packet (CIP), Connection
Management Procedures (CMP) and Function Control Protocol (FCP).

An iec61883 compliant driver exports two device nodes for isochronous
and for asynchronous transactions. See the FILES section of this man
page for the namespace definition.

Isochronous Transfers

Two methods are provided to receive/transmit isochronous data: using
mmap(2) in combination with ioctl(2), and read(2) or write(2).

Mmap/Ioctl
This method provides better performance and finer-grained control than
read/write, and is a method of choice for most applications. The data
buffer is mapped into a user process address space, which means no data
copying between the kernel and an application is necessary.
Synchronization between user processes and the driver is performed
using ioctl(2) commands.

An application allocates resources for isochronous transfer using
IEC61883_ISOCH_INIT. Then the data buffer can be mapped into the
process space using mmap(2).

A circular data buffer consists of one or more equal size frame buffers
(further referred to as frames, unless to avoid ambiguity with AV
frames). Frames are numbered starting with zero and are always
transferred sequentially. Frames consist equal sized packets. Each
packet contains a CIP header and one or more data blocks.

A driver and an application act as a producer and a consumer: producer
supplies full frames (filled with data) to the consumer, and the
producer is not allowed to access those frames until the consumer
claims them empty.

A transfer can be initiated and suspended with IEC61883_START and
IEC61883_STOP commands respectively. IEC61883_RECV or IEC61883_XMIT is
used for producer-consumer synchronization.

Read/Write
Using this method, an application calls read(2) or write(2) to receive
or transmit a specified amount of data. Bus-specific overhead, such as
isochronous packet headers, is handled by the driver and is not exposed
to applications. Data returned by read(2) contains CIP headers and
data blocks. Empty packets are not returned by read(2). write(2) data
should meet the same requirements.

If one or more channels have been allocated since open(2) (see
IEC61883_ISOCH_INIT), the data is received/transmitted using channel
that was created the last.

If no channels were allocated, the driver uses the broadcast channel by
default and allocates the default-size data buffer. During transmit,
the first packet's CIP header is used to auto-detect the data format.
If it is one of the formats supported by the driver, it is properly
transmitted (with inserted empty packets and timestamps).

For both methods, if during transmit the driver runs out of data, it
transmits empty packets containing only a CIP header of the next to be
transmitted packet, as defined in IEC 61883-1.

Connection Management Procedures

Applications wishing to follow Connection Management Procedures (CMP)
in combination with isochronous transfers should use the ioctl(2)
IEC61883_PLUG_INIT, IEC61883_PLUG_FINI, IEC61883_PLUG_REG_READ and
IEC61883_PLUG_REG_CAS commands.

Asynchronous Transactions

read(2), write(2), ioctl(2), and poll(2) can be used with asynchronous
nodes. Asynchronous data exchange between a driver and an application
utilizes a common data structure called asynchronous request (ARQ):

typedef struct iec61883_arq {
int arq_type;
int arq_len;
union {
uint32_t quadlet;
uint64_t octlet;
uint8_t buf[8];
} arq_data;
} iec61883_arq_t;

arq_type contains ARQ type:

IEC61883_ARQ_FCP_CMD
IEC61883_ARQ_FCP_RESP

FCP command and response frame respectively. Outgoing frames are
sent using write(2), incoming frames are received with read(2).

See IIEC 61883-1 for the FCP frame structure definition.

IEC61883_ARQ_BUS_RESET

Returned by the driver when a bus reset occurs. There is no data
associated with this request type, and arq_len is set to 0.

If arq_len is 4 or 8, then data should be supplied in arq_data.quadlet
or arq_data.octlet respectively, otherwise up to 8 bytes can be put in
arq_data.buf, with the rest of the data following immediately after.

write(2)
For a request to be sent to a target, an iec61883_arq_t structure along
with associated data is passed to the driver using write(2). write(2)
blocks until the request is completed.

read(2)
A driver collects incoming ARQs in the internal buffer. Buffer size
can be changed using the ioctl(2) command IEC61883_FCP_SET_IBUF_SIZE.

Reading an ARQ takes one or two steps depending on data length. An
application first reads `sizeof (iec61883_arq_t)' bytes: if arq_len is
less than or equal 4, which is usually the case, no additional step is
needed. Otherwise, the remaining `arq_len - 4' bytes should be read
and concatenated.

read(2) blocks until the specified amount of data is available, unless
O_NONBLOCK or O_NDELAY flag was set during open(2), in which case
read(2) returns immediately.

poll(2)
Applications can poll(2) asynchronous nodes on the POLLIN event.

Bus Reset

In case of a bus reset, the driver notifies an application by
generating an ARQ of type IEC61883_ARQ_BUS_RESET.

If there were established isochronous connections before bus reset, the
driver attempts to restore all connections as described in IEC 61883
and resume any active transfers that were in progress.

IOCTLS

The following commands only apply to isochronous nodes:

IEC61883_ISOCH_INIT

This command allocates a data buffer and isochronous resources (if
necessary) for the isochronous transfer. The argument is a pointer
to the structure:

typedef struct iec61883_isoch_init {
int ii_version; /* interface version */
int ii_pkt_size; /* packet size */
int ii_frame_size; /* packets/frame */
int ii_frame_cnt; /* # of frames */
int ii_direction; /* xfer direction */
int ii_bus_speed; /* bus speed */
uint64_t ii_channel; /* channel mask */
int ii_dbs; /* DBS */
int ii_fn; /* FN */
int ii_rate_n; /* rate numerator */
int ii_rate_d; /* rate denominator */
int ii_ts_mode; /* timestamp mode */
int ii_flags; /* flags */
int ii_handle; /* isoch handle */
int ii_frame_rcnt; /* # of frames */
off_t *ii_mmap_off /* mmap offset */
int ii_rchannel; /* channel */
int ii_error; /* error code */
} iec61883_isoch_init_t;

ii_version should be set to IEC61883_V1_0.

The driver attempts to allocate a data buffer consisting of
ii_frame_cnt frames, with ii_frame_size packets in each frame.
Packet size in bytes is specified by ii_pkt_size specifies and
should be a multiple of 512 and compatible with ii_bus_speed.

ii_direction can take one of the following values:

IEC61883_DIR_RECV Receiving isochronous data.

IEC61883_DIR_XMIT Transmitting isochronous data.

ii_bus_speed chooses bus speed to be used and can be either
IEC61883_S100, IEC61883_S200 or IEC61883_S400.

ii_channel is a mask that specifies an isochronous channel number to
be used, with the Nth bit representing channel N. When transmitting
data, several bits can be set at a time, in which case the driver
chooses one, for example, 0x3FF means a range from 0 to 9. In case
of receive, only one bit can be set.

ii_dbs specifies data block size in quadlets, for example, DBS value
for SD-DVCR is 0x78. Refer to IEC 61883 for more details on DBS.

ii_fn specifies fraction number, which defines the number of blocks
in which a source packet is divided. Allowed values are from 0 to
3. Refer to IEC 61883 for more details on FN.

Data rate expected by the AV device can be lower than the bus speed,
in which case the driver has to periodically insert empty packets
into the data stream to avoid device buffer overflows. This rate is
specified with a fraction N/D, set by ii_rate_n and ii_rate_d
respectively. Any integer numbers can be used, or the following
predefined constants:

IEC61883_RATE_N_DV_NTSC
IEC61883_RATE_D_DV_NTSC Data rate expected by DV-NTSC devices.

IEC61883_RATE_N_DV_PAL
IEC61883_RATE_D_DV_PAL Data rate expected by DV-PAL devices.

During data transmission, a timestamp based on the current value of
the cycle timer is usually required. ii_ts_mode defines timestamp
mode to be used:

IEC61883_TS_SYT Driver puts a timestamp in the SYT field of the
first CIP header of each frame.

IEC61883_TS_NONE No timestamps.

ii_dbs, ii_fn, ii_rate_n, ii_rate_d and ii_ts_mode are only required
for transmission. In other case these should be set to 0.

ii_flags should be set to 0.

If command succeeds, ii_handle contains a handle that should be used
with other isochronous commands. ii_frame_rcnt contains the number
of allocated frames (can be less than ii_frame_cnt). ii_mmap_off
contains an offset to be used in mmap(2), for example, to map an
entire data receive buffer:

pa = mmap(NULL, init.ii_pkt_size *
init.ii_frame_size * init.ii_frame_rcnt,
PROT_READ, MAP_PRIVATE, fd, init.ii_mmap_off);

ii_rchannel contains channel number.

In case of command success, ii_error is set to 0; otherwise one of
the following values can be returned:

IEC61883_ERR_NOMEM Not enough memory for the data buffer.

IEC61883_ERR_NOCHANNEL Cannot allocate isochronous channel.

IEC61883_ERR_PKT_SIZE Packet size is not allowed at this bus
speed.

IEC61883_ERR_VERSION Interface version is not supported.

IEC61883_ERR_INVAL One or more the parameters are invalid

IEC61883_ERR_OTHER Unspecified error type.

IEC61883_ISOCH_FINI

Argument is a handle returned by IEC61883_ISOCH_INIT. This command
frees any resources associated with this handle. There must be no
active transfers and the data buffer must be unmapped; otherwise the
command fails.

IEC61883_START

This command starts an isochronous transfer. The argument is a
handle returned by IEC61883_ISOCH_INIT.

IEC61883_STOP

This command stops an isochronous transfer. The argument is a
handle returned by IEC61883_ISOCH_INIT.

IEC61883_RECV

This command is used to receive full frames and return empty frames
to the driver. The argument is a pointer to the structure:

typedef struct iec61883_recv {
int rx_handle; /* isoch handle */
int rx_flags; /* flags */
iec61883_xfer_t rx_xfer; /* xfer params */
} iec61883_recv_t;

typedef struct iec61883_xfer {
int xf_empty_idx; /* first empty frame */
int xf_empty_cnt; /* empty frame count */
int xf_full_idx; /* first full frame */
int xf_full_cnt; /* full frame count */
int xf_error; /* error */
} iec61883_xfer_t;

rx_flags should be set to 0.

An application sets xf_empty_idx and xf_empty_cnt to indicate frames
it no longer needs. E. g. if a buffer consists of 6 frames,
xf_empty_idx is 4, xf_empty_cnt is 3 - means that frames 4, 5 and 0
can now be reused by the driver. If there are no empty frames, for
example, the first time this command is called, xf_empty_cnt should
be set to 0.

When the command returns, xf_full_idx and xf_full_cnt specifies the
frames that are full. xf_error is always 0.

In general, AV frame boundaries are not aligned with the frame
buffer boundaries, because the first received packet might not be
the first packet of an AV frame, and, in contrast with the
read/write method, the driver does not remove empty CIP packets.

Applications should detect empty packets by comparing adjacent
packets' continuity counters (DBC field of the CIP header).

IEC61883_XMIT

This command is used to transmit full frames and get more empty
frames from the driver. The argument is a pointer to the structure:

typedef struct iec61883_xmit {
int tx_handle; /* isoch handle */
int tx_flags; /* flags */
iec61883_xfer_t tx_xfer; /* xfer params */
int tx_miss_cnt; /* missed cycles */
} iec61883_xmit_t;

tx_flags should be set to zero.

The application sets xf_full_idx and xf_full_cnt to specify frames
it wishes to transmit. If there are no frames to transmit (e. g.
the first time this command is called), xf_full_cnt should be set to
0.

When the command returns, xf_empty_idx and xf_empty_cnt specifies
empty frames which can be to transmit more data. xf_error is always
0.

tx_miss_cnt contains the number of isochronous cycles missed since
last transfer due to data buffer under run. This can happen when an
application does not supply data fast enough. For the purposes of
time stamping, the driver considers the first packet in a frame
buffer to be the first packet of an AV frame.

IEC61883_PLUG_INIT

This command returns a handle for the specified plug. The argument
is a pointer to the structure:

typedef struct iec61883_plug_init {
int pi_ver; /* interface version */
int pi_loc; /* plug location */
int pi_type; /* plug type */
int pi_num; /* plug number */
int pi_flags; /* flags */
int pi_handle; /* plug handle */
int pi_rnum; /* plug number */
} iec61883_plug_init_t;

pi_ver should be set to IEC61883_V1_0.

pi_loc specifies plug location:

IEC61883_LOC_LOCAL On the local unit (local plug). A plug control
register (PCR) is allocated. Command fails if
the plug already exists

IEC61883_LOC_REMOTE On the remote unit (remote plug). The plug
should exist on the remote unit, otherwise the
command fails.

pi_type specifies isochronous plug type:

IEC61883_PLUG_IN
IEC61883_PLUG_OUT

Input or output plugs.

IEC61883_PLUG_MASTER_IN
IEC61883_PLUG_MASTER_OUT

Master input or master output plug. These plugs always exist on
the local unit.

pi_num specifies plug number. This should be 0 for master plugs,
and from 0 to 31 for input/output plugs. Alternatively, a special
value IEC61883_PLUG_ANY can be used to let the driver choose a free
plug number, create the plug and return the number in pi_rnum.

pi_flags should be set to 0.

If the command succeeds, pi_handle contains a handle that should be
used with other plug commands.

IEC61883_PLUG_FINI

Argument is a handle returned by IEC61883_PLUG_INIT. This command
frees any resources associated with this handle, including the PCR.

IEC61883_PLUG_REG_READ

Read plug register value. The argument is a pointer to the
structure:

typedef struct iec61883_plug_reg_val {
int pr_handle; /* plug handle */
uint32_t pr_val; /* register value */
} iec61883_plug_reg_val_t;

pr_handle is a handle returned by IEC61883_PLUG_INIT. Register
value is returned in pr_val.

IEC61883_PLUG_REG_CAS

Atomically compare and swap plug register value. The argument is a
pointer to the structure:

typedef struct iec61883_plug_reg_lock {
int pl_handle; /* plug handle */
uint32_t pl_arg; /* compare arg */
uint32_t pl_data; /* write value */
UINT32_t pl_old; /* original value */
} iec61883_plug_reg_lock_t;

pr_handle is a handle returned by IEC61883_PLUG_INIT.

Original register value is compared with pl_arg and if they are
equal, register value is replaced with pl_data. In any case, the
original value is stored in pl_old.

The following commands only apply to asynchronous nodes:

IEC61883_ARQ_GET_IBUF_SIZE

This command returns current incoming ARQ buffer size. The argument
is a pointer to int.

IEC61883_ARQ_SET_IBUF_SIZE

This command changes incoming ARQ buffer size. The argument is the
new buffer size in bytes.

FILES

/dev/av/N/async Device node for asynchronous data

/dev/av/N/isoch Device has been disconnected

ERRORS

EIO Bus operation failed. DMA failure.

EFAULT ioctl(2) argument points to an illegal address.

EINVAL Invalid argument or argument combination.

ENODEV Device has been disconnected.

ARCHITECTURE

All

INTERFACE STABILITY

Committed