feedback: BLE_GAP_DEVNAME_MAX_LEN is too short

[pabigot]

The core specification v4.0 vol 3 part C section 3.2.2.3 "Bluetooth Device Name -- Representation" states that the device name can be up to 248 bytes. I've confirmed that sd_ble_gap_device_name_set rejects long device names, consistent with BLE_GAP_DEVNAME_MAX_LEN being 31 in the S110 v 7.1.0 soft device.

We may be able to make do with 31 chars but there are cases (especially for non-European languages using UTF-8 encoding) where that may be a significant limitation. Does Bluetooth allow an implementation to reject the full length? (Yes I know longer ones won't fit in advertising/reponse packets but you can retrieve UUID 2a00 directly to get the full name.)

[Petter Myhre]

Thank you for the feedback.

Yes, the Bluetooth spec allows it. It says "The Bluetooth device name can be up to 248 bytes".

Earlier it was 20 bytes, but we have increased it 31 bytes.

[pabigot]

While the line I cited does say "can be up to 248 bytes", Vol 1 Part E section 1.6 states that "can" is informative, not normative, and may be read as "is able to". Volume 2 Part C section 4.3.5 repeats the 248 byte maximum but does not use normative language nor suggest a minimum that must be supported.

I expect the answer can be found somewhere in the 2771 pages of Core V4.2, and hoped somebody would know where, just to satisfy curiosity. It's not that important, though.