Hi Christian, On Mon, Oct 17, 2022 at 7:57 AM Christian Eggers <ceggers@xxxxxxx> wrote: > > When monitoring a Bluetooth connection between two Linux systems > (kernel 5.14 / 5.15 + bluez-5.65), I noticed the following: > > > HCI Event: LE Meta Event (0x3e) plen 12 #21108 [hci0] 1650.255887 > LE Read Remote Used Features (0x04) > Status: Success (0x00) > Handle: 25 Address: 00:1A:7D:F0:21:40 (OUI 00-1A-7D) > Features: 0xbd 0x5f 0x66 0x00 0x00 0x00 0x00 0x00 > ... > LE Data Packet Length Extension > ... > > > ACL Data RX: Handle 25 flags 0x02 dlen 18 #21109 [hci0] 1650.300224 > LE L2CAP: LE Connection Request (0x14) ident 1 len 10 > PSM: 128 (0x0080) > Source CID: 64 > MTU: 672 > MPS: 23 > Credits: 30 > < ACL Data TX: Handle 25 flags 0x00 dlen 18 #21110 [hci0] 1650.300431 > LE L2CAP: LE Connection Response (0x15) ident 1 len 10 > Destination CID: 64 > MTU: 672 > MPS: 23 > Credits: 30 > Result: Connection successful (0x0000) > ... > > HCI Event: LE Meta Event (0x3e) plen 11 #21113 [hci0] 1650.345822 > LE Data Length Change (0x07) > Handle: 25 Address: 00:1A:7D:F0:21:40 (OUI 00-1A-7D) > Max TX octets: 251 > Max TX time: 2120 > Max RX octets: 251 > Max RX time: 2120 > > I can't find that HCI_EV_LE_DATA_LEN_CHANGE is implemented anywhere in the kernel nor in bluez userspace. > So why do I get this event? Is it generated by controller firmware itself? We do programm the it earlier though with HCI_OP_LE_WRITE_DEF_DATA_LEN: https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git/tree/net/bluetooth/hci_sync.c#n4362 > I think that both adapters support DLE. Is there there already support for using it with Linux? I guess it would probably make sense to handle HCI_EV_LE_DATA_LEN_CHANGE, that said it seems to come after the L2CAP Connection Request in case you are suggesting to align the MTU with Max TX/RX length. > regards > Christian > > > -- Luiz Augusto von Dentz
