CM748-ugreen-bluetooth-adapter-patch-linux

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CM748-ugreen-bluetooth-adapter-patch-linux

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Kernel patch to restore Bluetooth functionality on Linux for the Ugreen CM748 5.4 bluetooth adapter.

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최종 버전 다운로드 (.zip)

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# UGREEN CM748 Bluetooth 5.4 Adapter — Linux Kernel Patch

> [!IMPORTANT]
> **This issue has been officially fixed in the Linux kernel.** The fix was merged into mainline **6.18** (commit [`7722d6fb54e4`](https://github.com/torvalds/linux/commit/7722d6fb54e428a8f657fccf422095a8d7e2d72c)) and backported to LTS branches **6.12.58+** and **6.6.117+**. If your kernel is at or above these versions, you just need to update your system — no patching required. This repo is kept around for anyone stuck on older kernels.

A kernel patch to get the **UGREEN CM748** (USB ID `33fa:0010`, Barrot BR8654/BR8554 chipset) Bluetooth adapter working on Linux.

## What's going on?

The Barrot chip inside the CM748 has a firmware bug — it doesn't properly respond to the `HCI_Read_Local_Extended_Features` command during Bluetooth initialization. When Linux sends this command, the adapter just hangs and refuses to power on.

If you check `dmesg` after plugging it in, you'll see something like:

```
Bluetooth: hci0: command 0x1004 tx timeout
Bluetooth: hci0: HCI command 0x1004 failed (-110)
```

## What does this patch do?

It removes two calls to `hci_read_local_ext_features` from the Bluetooth HCI init sequence in `net/bluetooth/hci_sync.c`. Without those calls, the kernel doesn't try to send the command the adapter can't handle, and it initializes just fine.

This **won't** break other Bluetooth adapters — the removed feature query isn't essential for normal operation.

## Credits

This patch is based on [this AskUbuntu answer](https://askubuntu.com/a/1550592). I just wrapped it up as an easy-to-apply patch file.

---

## Quick sanity check

Before diving into patching, make sure the adapter is actually detected and the symptoms match:

```bash
# Check if the adapter shows up on USB
lsusb | grep -i "33fa"
# You should see: Bus XXX Device XXX: ID 33fa:0010 ...

# Look for Bluetooth errors in the kernel log
dmesg | grep -i bluetooth

# Make sure it's not just RF-blocked
rfkill list
```

If `lsusb` doesn't show the device at all, you've got a hardware or connection issue — this patch won't help with that.

---

## How to apply the patch

### Option 1: CachyOS (GUI method)

If you're on CachyOS, the whole thing is pretty straightforward:

1. Download [`0001-bluetooth-disable-read-local-ext-features.patch`](https://github.com/nwrafael/CM748-ugreen-bluetooth-adapter-patch-linux/releases/download/V1.0/0001-bluetooth-disable-read-local-ext-features.patch).
2. Open **CachyOS Kernel Manager**.
3. Pick the kernel you're currently running.
4. Hit **Configure** → go to the **Patches** tab.
5. Click **Add Local Patch** and select the file you downloaded.
6. Go back to the **Options** tab and click **Build Kernel**.
7. Wait for the build to finish (might take a while depending on your hardware), then reboot.

---

### Option 2: Rebuild just the Bluetooth module (any distro, faster)

Instead of rebuilding the entire kernel, you can rebuild **only** the Bluetooth module. Same setup, but the compile step takes seconds instead of hours.

#### Step 1 — Install kernel headers and build dependencies

You'll need both the build tools **and** the kernel headers package for your running kernel. The headers package provides `Module.symvers`, which is needed for the module to load correctly.

<details>
<summary>Debian / Ubuntu / Linux Mint / Pop!_OS</summary>

```bash
sudo apt update
sudo apt install build-essential libncurses-dev bison flex libssl-dev libelf-dev bc dwarves rsync \
 linux-headers-$(uname -r)
```
</details>

<details>
<summary>Fedora / CentOS / RHEL / AlmaLinux</summary>

```bash
sudo dnf groupinstall "Development Tools"
sudo dnf install ncurses-devel openssl-devel elfutils-libelf-devel bc flex bison dwarves \
 kernel-devel-$(uname -r)
```
</details>

<details>
<summary>Arch Linux / Manjaro / EndeavourOS</summary>

```bash
sudo pacman -S base-devel bc xmlto docbook-xsl kmod inetutils linux-headers
```
</details>

<details>
<summary>openSUSE</summary>

```bash
sudo zypper install -t pattern devel_kernel
sudo zypper install ncurses-devel libopenssl-devel libelf-devel bc flex bison dwarves \
 kernel-devel
```
</details>

<details>
<summary>Void Linux</summary>

```bash
sudo xbps-install base-devel ncurses-devel libressl-devel elfutils-devel bc flex bison perl \
 linux-headers-$(uname -r | cut -d. -f1-2)
```
</details>

#### Step 2 — Download and extract the kernel source

```bash
# Check your version
uname -r

# Download the matching version (replace X.Y.Z)
wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-X.Y.Z.tar.xz
tar xf linux-X.Y.Z.tar.xz
cd linux-X.Y.Z
```

> You can browse available versions at [kernel.org](https://www.kernel.org/).

#### Step 3 — Apply the patch

```bash
cp /path/to/0001-bluetooth-disable-read-local-ext-features.patch .
patch -p1 < 0001-bluetooth-disable-read-local-ext-features.patch
```

You should see:

```
patching file net/bluetooth/hci_sync.c
```

If you get errors like `Hunk #1 FAILED`, check the [Troubleshooting](#troubleshooting) section below.

#### Step 4 — Prepare the build environment

Copy your running kernel's config and prepare the source tree for module building:

```bash
# Most distros:
cp /boot/config-$(uname -r) .config

# Arch Linux (if the above file doesn't exist):
# zcat /proc/config.gz > .config

make olddefconfig
scripts/config --disable SYSTEM_TRUSTED_KEYS
scripts/config --disable SYSTEM_REVOCATION_KEYS
make prepare
make modules_prepare
```

Now copy `Module.symvers` from your installed kernel headers — this is what makes sure the module is compatible with your running kernel:

```bash
cp /lib/modules/$(uname -r)/build/Module.symvers .
```

#### Step 5 — Build just the Bluetooth module

```bash
make M=net/bluetooth modules
```

This should finish in **under a minute**.

#### Step 6 — Install the patched module

Back up the original and drop in the new one:

```bash
# Find out what the current module file looks like
ls /lib/modules/$(uname -r)/kernel/net/bluetooth/bluetooth.ko*

# Back up the original
sudo cp /lib/modules/$(uname -r)/kernel/net/bluetooth/bluetooth.ko* \
       /lib/modules/$(uname -r)/kernel/net/bluetooth/bluetooth.ko.bak

# Copy the new module
sudo cp net/bluetooth/bluetooth.ko /lib/modules/$(uname -r)/kernel/net/bluetooth/bluetooth.ko

# If your distro compresses modules (check the ls output above), compress it to match:
# For .ko.zst:  sudo zstd --rm /lib/modules/$(uname -r)/kernel/net/bluetooth/bluetooth.ko
# For .ko.xz:   sudo xz /lib/modules/$(uname -r)/kernel/net/bluetooth/bluetooth.ko
# For .ko.gz:   sudo gzip /lib/modules/$(uname -r)/kernel/net/bluetooth/bluetooth.ko

# Update module dependencies
sudo depmod -a
```

#### Step 7 — Reboot

```bash
sudo reboot
```

After rebooting, check that it worked:

```bash
bluetoothctl show    # Should display the adapter's info
```

> **Heads up:** since you're replacing a module in an existing kernel, any kernel update from your distro will overwrite the patched module and you'd need to redo this. If that's annoying, consider the full kernel build in Option 3 instead.

---

### Option 3: Build the kernel yourself (any distro)

This works on **any** Linux distribution. It's the most involved option, but it gives you a fully self-contained patched kernel.

> ⚠️ Building a custom kernel is an advanced task. If something goes wrong, you can always boot into your old kernel from the GRUB menu. Still, having a recovery USB handy is a good idea.

#### Step 1 — Install build dependencies

<details>
<summary>Debian / Ubuntu / Linux Mint / Pop!_OS</summary>

```bash
sudo apt update
sudo apt install build-essential libncurses-dev bison flex libssl-dev libelf-dev bc dwarves rsync
```
</details>

<details>
<summary>Fedora / CentOS / RHEL / AlmaLinux</summary>

```bash
sudo dnf groupinstall "Development Tools"
sudo dnf install ncurses-devel openssl-devel elfutils-libelf-devel bc flex bison dwarves
```
</details>

<details>
<summary>Arch Linux / Manjaro / EndeavourOS</summary>

```bash
sudo pacman -S base-devel bc xmlto docbook-xsl kmod inetutils
```
</details>

<details>
<summary>openSUSE</summary>

```bash
sudo zypper install -t pattern devel_kernel
sudo zypper install ncurses-devel libopenssl-devel libelf-devel bc flex bison dwarves
```
</details>

<details>
<summary>Void Linux</summary>

```bash
sudo xbps-install base-devel ncurses-devel libressl-devel elfutils-devel bc flex bison perl
```
</details>

#### Step 2 — Download and extract the kernel source

Grab the source for your currently running kernel:

```bash
# Check your version
uname -r

# Download it (replace X.Y.Z with your version)
wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-X.Y.Z.tar.xz
tar xf linux-X.Y.Z.tar.xz
cd linux-X.Y.Z
```

> You can browse available versions at [kernel.org](https://www.kernel.org/).

#### Step 3 — Apply the patch

Copy the patch file into the kernel source directory and apply it:

```bash
cp /path/to/0001-bluetooth-disable-read-local-ext-features.patch .
patch -p1 < 0001-bluetooth-disable-read-local-ext-features.patch
```

You should see:

```
patching file net/bluetooth/hci_sync.c
```

If you get errors like `Hunk #1 FAILED`, check the [Troubleshooting](#troubleshooting) section below.

#### Step 4 — Configure the kernel

Use your current kernel's config as a starting point:

```bash
# Most distros:
cp /boot/config-$(uname -r) .config

# Arch Linux (if the above file doesn't exist):
# zcat /proc/config.gz > .config

make olddefconfig
```

> If the build later fails with certificate errors, run this beforehand:
> ```bash
> scripts/config --disable SYSTEM_TRUSTED_KEYS
> scripts/config --disable SYSTEM_REVOCATION_KEYS
> ```

#### Step 5 — Compile

```bash
make -j$(nproc)
```

> ⏱️ This takes a while — anywhere from **30 minutes to 2+ hours** depending on your CPU. Good time for a coffee break.

#### Step 6 — Install

```bash
sudo make modules_install
sudo make install
```

#### Step 7 — Update the bootloader

<details>
<summary>Debian / Ubuntu (GRUB)</summary>

```bash
sudo update-initramfs -c -k $(make kernelrelease)
sudo update-grub
```
</details>

<details>
<summary>Fedora / RHEL (GRUB2)</summary>

```bash
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
```
</details>

<details>
<summary>Arch Linux (GRUB)</summary>

```bash
sudo mkinitcpio -k $(make kernelrelease) -g /boot/initramfs-$(make kernelrelease).img
sudo grub-mkconfig -o /boot/grub/grub.cfg
```
</details>

<details>
<summary>systemd-boot</summary>

```bash
sudo kernel-install add $(make kernelrelease) /boot/vmlinuz-$(make kernelrelease)
```
</details>

#### Step 8 — Reboot

```bash
sudo reboot
```

Pick the new kernel from the GRUB menu if needed, then verify everything worked:

```bash
uname -r            # Should show your new version
bluetoothctl show    # Should display the adapter's info
```

---

## Troubleshooting

### Patch fails to apply (`Hunk FAILED`)

If your kernel version is pretty different from the one this patch was made for, the line numbers might have shifted. You can always apply the fix **by hand**:

1. Open `net/bluetooth/hci_sync.c` in your editor.
2. Search for `hci_read_local_ext_features_1_sync`.
3. Delete (or comment out) these two lines:
   ```c
   /* HCI_OP_READ_LOCAL_EXT_FEATURES */
   HCI_INIT(hci_read_local_ext_features_1_sync),
   ```
4. Search for `hci_read_local_ext_features_all_sync`.
5. Delete (or comment out) these two lines:
   ```c
   /* HCI_OP_READ_LOCAL_EXT_FEATURES */
   HCI_INIT(hci_read_local_ext_features_all_sync),
   ```
6. Save the file and continue the build from **Step 4**.

### Bluetooth still not working after patching

- Double-check you actually booted into the patched kernel: `uname -r`
- See if the adapter needs firmware files: `dmesg | grep -i firmware`
- Restart the Bluetooth service: `sudo systemctl restart bluetooth`
- Try turning it on manually: `bluetoothctl power on`

### Build fails with certificate/key errors

```bash
scripts/config --disable SYSTEM_TRUSTED_KEYS
scripts/config --disable SYSTEM_REVOCATION_KEYS
```

Then run `make -j$(nproc)` again.

### How to go back to your old kernel

If the patched kernel causes issues, just pick your previous kernel from the GRUB menu (hold **Shift** or press **Esc** during boot to get to the menu).

---

## License

This patch modifies GPL-licensed Linux kernel source code. Distributed under the same license (GPL-2.0).

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