I wrote a question about this on Unix & Linux StackExchange and was able to make a patch with help. Since I own a CM749 Bluetooth adapter like the OP and my patch worked for me, it could be implemented as a temporary workaround or be improved further.
Here is my Unix & Linux post: https://unix.stackexchange.com/questions/798251/what-does-it-mean-to- cancel-a-command-in-the-linux-kernel-and-how-can-one-do-s/798268#798268 I've added instructions for using it in Nixos (my machine), but the patch itself is based off the 6.15.7 mainline kernel so it could be used by any distro that uses the 'standard' kernel. ** Patch added: "My patch for CM749 compatibility" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2076407/+attachment/5893400/+files/cm749.patch -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2076407 Title: Title: Bluetooth 5.4 Adapter (Ugreen CM749) Not Functioning on Ubuntu 20.04 with Kernel 6.x Description: The Bluetooth 5.4 adapter Ugreen CM749 is not functioning on Ubuntu 20.04 with Kernel 6.x. The adapter is detected by the system but fails to initialize, showing a "Connection timed out (110)" error when attempting to bring up the interface. The Bluetooth 5.0 dongle works without issues on the same system. Steps to Reproduce: 1. Plugged in the Ugreen CM749 Bluetooth 5.4 adapter. 2. Ran `hciconfig hci0 up` to bring up the Bluetooth interface. 3. Observed the error "Connection timed out (110)" in the terminal. 4. Checked the dmesg logs and found repeated Bluetooth errors. Expected Behavior: The Bluetooth 5.4 adapter should initialize correctly, allowing for Bluetooth functionality such as pairing and connecting devices. Actual Behavior: The Bluetooth 5.4 adapter fails to initialize, with the interface staying down and connection attempts timing out. Additional Information: - Kernel Version: 6.10.2-061002-generic - Ubuntu Version: 20.04 - Hardware Information: *-network:1 description: Bluetooth device product: Realtek Bluetooth Adapter vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: usb@1:1 version: 1.00 - dmesg Output: [12345.6789] Bluetooth: hci0: Opcode 0x1005 failed: -110 - hciconfig Output: hci0: Type: Primary Bus: USB BD Address: 00:A7:45:28:00:B3 ACL MTU: 0:0 SCO MTU: 0:0 DOWN RX bytes:171 acl:0 sco:0 events:10 errors:0 TX bytes:276 acl:0 sco:0 commands:11 errors:0 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2076407/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
