Added a kernel module

Added new nix expr

Added patch

Updated

Updated patch

Renamed variables, bluetooth works on mt7925 now

config/btusb-add-mt7925.patch

@@ -0,0 +1,11 @@
+--- a/drivers/bluetooth/btusb.c
++++ b/drivers/bluetooth/btusb.c
+@@ -725,6 +725,8 @@ static const struct usb_device_id quirks_table[] = {
+ 						     BTUSB_WIDEBAND_SPEECH },
+ 	{ USB_DEVICE(0x13d3, 0x3630), .driver_info = BTUSB_MEDIATEK |
+ 						     BTUSB_WIDEBAND_SPEECH },
++	{ USB_DEVICE(0x2c7c, 0x7009), .driver_info = BTUSB_MEDIATEK |
++						     BTUSB_WIDEBAND_SPEECH },
+ 
+ 	/* Additional Realtek 8723AE Bluetooth devices */
+ 	{ USB_DEVICE(0x0930, 0x021d), .driver_info = BTUSB_REALTEK },

config/btusb.nix

@@ -0,0 +1,34 @@
+{ pkgs, lib, kernel ? pkgs.linuxPackages_latest.kernel}:
+
+pkgs.stdenv.mkDerivation {
+  pname = "btusb-kernel-module";
+  inherit (kernel) src version postPatch nativeBuildInputs;
+
+  kernel_dev = kernel.dev;
+  kernelVersion = kernel.modDirVersion;
+
+  # The key change is here: point to the correct module path for btusb.
+  modulePath = "drivers/bluetooth";
+
+  buildPhase = ''
+    BUILT_KERNEL=$kernel_dev/lib/modules/$kernelVersion/build
+    cp $BUILT_KERNEL/Module.symvers .
+    cp $BUILT_KERNEL/.config        .
+    cp $kernel_dev/vmlinux          .
+    make "-j$NIX_BUILD_CORES" modules_prepare
+    make "-j$NIX_BUILD_CORES" M=$modulePath modules
+  '';
+
+  installPhase = ''
+    make \
+      INSTALL_MOD_PATH="$out" \
+      XZ="xz -T$NIX_BUILD_CORES" \
+      M="$modulePath" \
+      modules_install
+  '';
+
+  meta = {
+    description = "btusb kernel module";
+    license = lib.licenses.gpl3;
+  };
+}