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jonas-schievink / rubble

(going to be a) BLE stack for embedded Rust
BSD Zero Clause License
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Remove flags, as they are not needed according to Bluetooth 4.2 specification #132

Closed elwerene closed 4 years ago

elwerene commented 4 years ago

Bluetooth specification 4.2:

9.2.2.2 Conditions
A device in the non-discoverable mode that sends advertising events shall not
set the ‘LE General Discoverable Mode’ flag or ‘LE Limited Discoverable Mode’
flag in the Flags AD type (see [Core Specification Supplement], Part A, Section
1.3). A Peripheral device in the non-connectable mode may send non-
connectable undirected advertising events or scannable undirected advertising
events or may not send advertising packets.

Sounds to me like sending no Flags AD is totally fine and correct (and saves 3 bytes).

jonas-schievink commented 4 years ago

That doesn't say that it is allowed to leave out the entire flags byte though. The flags structure also has a BR_EDR_NOT_SUPPORTED flag which we set. If that flag is required when classic BT is not supported, then we cannot leave out the flags.

jonas-schievink commented 4 years ago

Ah nevermind, the Core Specification Supplement says:

The Flags data type shall be included when any of the Flag bits are non-zero and the advertising packet is connectable, otherwise the Flags data type may be omitted.