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Robert Quattlebaum a24602e909 Refinement of Spinel Protocol Documentation (#534 )

This commit refines the documentation of the Spinel NCP protocol. What
was previously a single markdown-based document has now been broken
into multiple files which can be edited independently. These files can
then be compiled into a final document in either XML, HTML, or
plaintext formats. The [`mmark`](https://github.com/miekg/mmark) tool is
used for compiling the source documentation into a single XML file and
[`xml2rfc`](https://xml2rfc.tools.ietf.org/) is used to convert from
the XML to the final desired format.

Note that the building of the protocol documents is handled
independently from the normal OpenThread build. The spinel protocol
document source files are intentionally excluded from the build
system, since there is no value in including them. Copies of the final
compiled documents are included to ensure that they are distributed
with any release archives.

This commit is focused on introducing this new strucutre to the protocol
document. The document itself is a work in progress and may contain
errors or require revisions, hence the `draft-` prefix in the filenames.

This commit is related to issue #492, "☂ Spinel NCP Protocol
Standardization".

2016-09-09 10:36:45 -07:00

2.7 KiB

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Feature: Host Buffer Offload

The memory on an NCP may be much more limited than the memory on the host processor. In such situations, it is sometimes useful for the NCP to offload buffers to the host processor temporarily so that it can perform other operations.

Host buffer offload is an optional NCP capability that, when present, allows the NCP to store data buffers on the host processor that can be recalled at a later time.

The presence of this feature can be detected by the host by checking for the presence of the CAP_HBO capability in PROP_CAPS.

Commands

CMD 12: (NCP->Host) CMD_HBO_OFFLOAD

Argument-Encoding: LscD
- OffloadId: 32-bit unique block identifier
- Expiration: In seconds-from-now
- Priority: Critical, High, Medium, Low
- Data: Data to offload

CMD 13: (NCP->Host) CMD_HBO_RECLAIM

Argument-Encoding: Lb
- OffloadId: 32-bit unique block identifier
- KeepAfterReclaim: If not set to true, the block will be dropped by the host after it is sent to the NCP.

CMD 14: (NCP->Host) CMD_HBO_DROP

Argument-Encoding: L
- OffloadId: 32-bit unique block identifier

CMD 15: (Host->NCP) CMD_HBO_OFFLOADED

Argument-Encoding: Li
- OffloadId: 32-bit unique block identifier
- Status: Status code for the result of the operation.

CMD 16: (Host->NCP) CMD_HBO_RECLAIMED

Argument-Encoding: LiD
- OffloadId: 32-bit unique block identifier
- Status: Status code for the result of the operation.
- Data: Data that was previously offloaded (if any)

CMD 17: (Host->NCP) CMD_HBO_DROPPED

Argument-Encoding: Li
- OffloadId: 32-bit unique block identifier
- Status: Status code for the result of the operation.

Properties

PROP 10: PROP_HBO_MEM_MAX

Type: Read-Write
Packed-Encoding: L

Octets:	4
Fields:	`PROP_HBO_MEM_MAX`

Describes the number of bytes that may be offloaded from the NCP to the host. Default value is zero, so this property must be set by the host to a non-zero value before the NCP will begin offloading blocks.

This value is encoded as an unsigned 32-bit integer.

This property is only available if the CAP_HBO capability is present in PROP_CAPS.

PROP 11: PROP_HBO_BLOCK_MAX

Type: Read-Write
Packed-Encoding: S

Octets:	2
Fields:	`PROP_HBO_BLOCK_MAX`

Describes the number of blocks that may be offloaded from the NCP to the host. Default value is 32. Setting this value to zero will cause host block offload to be effectively disabled.

This value is encoded as an unsigned 16-bit integer.