2016-05-23 15:09:57 +08:00
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BTSnoop/Monitor protocol formats
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********************************
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TTY-based protocol
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==================
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This section covers the protocol that can be parsed by btmon when
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passing it the --tty parameter. The protocol is little endian, packet
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based, and has the following header for each packet:
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struct tty_hdr {
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uint16_t data_len;
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uint16_t opcode;
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uint8_t flags;
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uint8_t hdr_len;
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uint8_t ext_hdr[0];
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} __attribute__ ((packed));
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The actual payload starts at ext_hdr + hdr_len and has the length of
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data_len - 4 - hdr_len. Each field of the header is defined as follows:
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data_len:
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This is the total length of the entire packet, excuding the
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data_len field itself.
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opcode:
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The BTSnoop opcode
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flags:
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Special flags for the packet. Currently no flags are defined.
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hdr_len:
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Length of the extended header.
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ext_hdr:
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This is a sequence of header extension fields formatted as:
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struct {
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uint8_t type;
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uint8_t value[length];
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}
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The length of the value is dependent on the type. Currently the
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following types are defined:
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Type Length Meaning
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----------------------------------------------------------------
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1 Command drops 1 byte Dropped HCI command packets
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2 Event drops 1 byte Dropped HCI event packets
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3 ACL TX drops 1 byte Dropped ACL TX packets
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4 ACL RX drops 1 byte Dropped ACL RX packets
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5 SCO TX drops 1 byte Dropped SCO TX packets
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6 SCO RX drops 1 byte Dropped SCO RX packets
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7 Other drops 1 byte Dropped other packets
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8 32-bit timestamp 4 bytes Timestamp in 1/10th ms
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2016-05-25 15:16:54 +08:00
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The drops fields indicate the number of packets that the
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implementation had to drop (e.g. due to lack of buffers) since
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the last reported drop count.
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2016-05-23 15:09:57 +08:00
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The fields of the extended header must be sorted by increasing
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type. This is essential so that unknown types can be ignored and
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the parser can jump to processing the payload.
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