Hi, I have installed many distributions and in all of them with kernel versions 5.x, bluetooth adapter doesn't get detected in the dmesg log. There is no hci0 device detection in dmesg. I have a dual boot setup with windows 10. In windows, bluetooth works fine. However, if I install a distribution with 4.19.x kernel or install ubuntu's 4.19.x kernel on a distro and boot from that kernel, my hci0 bluetooth adapter gets detected and works fine. My bluetooth adapter is realtek rtl8723d. Also, the adapter gets detected even in the newer kernels if it is in a virtual machine, but not in dual boot.
Moreover, once I am in the older kernel in linux and bluetooth is working fine, if I boot into newer kernel, obviously, bluetooth doesn't work in that, but now, even if I reboot into older kernel, bluetooth stops working there too! Then I have to boot at least once into windows to make bluetooth work in the 4.19.x kernels. It seems like the newer kernel sort of leaves the adapter in a useless state which is restored only by Windows.

Can anybody please tell me why bluetooth adapter is not getting detected in newer kernels and how can I make it work?

I would say the device driver is missing. probably this helps: https://askubuntu.com/questions/1012...-for-chip-id-2

I do not think this is a firmware issue, as I have placed the rtl_bt folder containing the firmware in /lib/firmware/ and the bluetooth adapter is still not detected. In Debian with kernel 4.19, I could see the hci0 getting detected in dmesg but it could not load firmware as there was no rtl_bt folder in /lib/firmware/ . When I placed the rtl_bt folder there, bluetooth started working.

so need to check what is in the log files about detection.

Here is the output of sudo dmesg | grep Blue on older kernels :

[ 12.264937] Bluetooth: Core ver 2.22
[ 12.264947] Bluetooth: HCI device and connection manager initialized
[ 12.264948] Bluetooth: HCI socket layer initialized
[ 12.264950] Bluetooth: L2CAP socket layer initialized
[ 12.264952] Bluetooth: SCO socket layer initialized
[ 12.402352] Bluetooth: hci0: RTL: rtl: examining hci_ver=08 hci_rev=000d lmp_ver=08 lmp_subver=8723
[ 12.403335] Bluetooth: hci0: RTL: rom_version status=0 version=2
[ 12.403336] Bluetooth: hci0: RTL: rtl: loading rtl_bt/rtl8723d_fw.bin
[ 12.440366] Bluetooth: hci0: RTL: rtl: loading rtl_bt/rtl8723d_config.bin
[ 18.871947] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[ 18.871947] Bluetooth: BNEP filters: protocol multicast
[ 18.871950] Bluetooth: BNEP socket layer initialized
[ 29.993005] Bluetooth: RFCOMM TTY layer initialized
[ 29.993010] Bluetooth: RFCOMM socket layer initialized
[ 29.993013] Bluetooth: RFCOMM ver 1.11

Here is the same command's output for newer kernels:

[ 95.362787] Bluetooth: Core ver 2.22
[ 95.362811] Bluetooth: HCI device and connection manager initialized
[ 95.362815] Bluetooth: HCI socket layer initialized
[ 95.362817] Bluetooth: L2CAP socket layer initialized
[ 95.362820] Bluetooth: SCO socket layer initialized

Also, in newer kernels, Realtek Semiconductor Corp. entry is missing from lsusb

can you check the diff in kernel modules too? (lsmod)

Here is lsmod results from mxlinux with 4.19.x kernel on which bluetooth works:

Module Size Used by
rfcomm 86016 16
fuse 122880 4
cpufreq_userspace 16384 0
cpufreq_powersave 16384 0
cpufreq_conservative 16384 0
cmac 16384 1
bnep 24576 2
uinput 20480 1
nfsd 425984 2
auth_rpcgss 73728 1 nfsd
nfs_acl 16384 1 nfsd
nfs 311296 0
lockd 118784 2 nfsd,nfs
grace 16384 2 nfsd,lockd
fscache 385024 1 nfs
sunrpc 425984 6 nfsd,auth_rpcgss,lockd,nfs_acl,nfs
parport_pc 32768 0
ppdev 20480 0
lp 20480 0
parport 57344 3 parport_pc,lp,ppdev
dm_crypt 40960 0
snd_hda_codec_hdmi 57344 1
snd_hda_codec_realtek 122880 1
snd_hda_codec_generic 86016 1 snd_hda_codec_realtek
wl 6463488 0
uvcvideo 118784 0
videobuf2_vmalloc 16384 1 uvcvideo
videobuf2_memops 16384 1 videobuf2_vmalloc
videobuf2_v4l2 28672 1 uvcvideo
videobuf2_common 53248 2 videobuf2_v4l2,uvcvideo
videodev 212992 3 videobuf2_v4l2,uvcvideo,videobuf2_common
i915 1732608 11
media 45056 2 videodev,uvcvideo
btusb 53248 0
btrtl 16384 1 btusb
btbcm 16384 1 btusb
btintel 24576 1 btusb
bluetooth 647168 41 btrtl,btintel,btbcm,bnep,btusb,rfcomm
snd_soc_skl 114688 0
intel_rapl 24576 0
snd_soc_skl_ipc 73728 1 snd_soc_skl
cfg80211 774144 1 wl
drbg 28672 1
x86_pkg_temp_thermal 16384 0
ansi_cprng 16384 0
intel_powerclamp 16384 0
snd_soc_sst_ipc 16384 1 snd_soc_skl_ipc
snd_soc_sst_dsp 36864 1 snd_soc_skl_ipc
snd_hda_ext_core 28672 1 snd_soc_skl
ecdh_generic 24576 2 bluetooth
snd_soc_acpi_intel_match 24576 1 snd_soc_skl
coretemp 16384 0
crc16 16384 1 bluetooth
snd_soc_acpi 16384 2 snd_soc_acpi_intel_match,snd_soc_skl
snd_soc_core 253952 1 snd_soc_skl
kvm_intel 233472 0
kvm 749568 1 kvm_intel
joydev 24576 0
irqbypass 16384 1 kvm
crct10dif_pclmul 16384 0
crc32_pclmul 16384 0
crc32c_intel 24576 0
ghash_clmulni_intel 16384 0
pcbc 16384 0
aesni_intel 200704 2
drm_kms_helper 208896 1 i915
r8169 90112 0
snd_compress 24576 1 snd_soc_core
drm 495616 7 drm_kms_helper,i915
aes_x86_64 20480 1 aesni_intel
crypto_simd 16384 1 aesni_intel
cryptd 28672 3 crypto_simd,ghash_clmulni_intel,aesni_intel
glue_helper 16384 1 aesni_intel
realtek 20480 0
snd_hda_intel 45056 3
intel_cstate 16384 0
wmi_bmof 16384 0
snd_hda_codec 151552 4 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec_realtek
libphy 77824 3 r8169,realtek
intel_uncore 135168 0
psmouse 172032 0
efi_pstore 16384 0
snd_hda_core 94208 7 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel,snd_hda_ext_core,snd_hda_codec,snd_hda_codec_ realtek,snd_soc_skl
efivars 20480 1 efi_pstore
processor_thermal_device 16384 0
intel_soc_dts_iosf 16384 1 processor_thermal_device
snd_hwdep 16384 1 snd_hda_codec
snd_pcm 114688 7 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_ext_core,snd_hda_codec,snd_soc_core,snd_soc_skl,snd_hda_cor e
sg 36864 0
snd_timer 36864 1 snd_pcm
snd 94208 16 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hwdep,snd_hda_intel,snd_hda_codec,snd_hda_codec_realtek ,snd_timer,snd_compress,snd_soc_core,snd_pcm
mei_me 45056 0
iTCO_wdt 16384 0
iTCO_vendor_support 16384 1 iTCO_wdt
mei 118784 1 mei_me
soundcore 16384 1 snd
i2c_i801 28672 0
pcc_cpufreq 16384 0
thermal 20480 0
ac 16384 0
video 45056 1 i915
tpm_crb 16384 0
tpm_tis 16384 0
tpm_tis_core 20480 1 tpm_tis
tpm 65536 3 tpm_tis,tpm_crb,tpm_tis_core
rng_core 16384 1 tpm
hp_wmi 16384 0
sparse_keymap 16384 1 hp_wmi
serio_raw 16384 0
rfkill 28672 5 hp_wmi,bluetooth,cfg80211
acpi_pad 24576 0
acpi_tad 16384 0
intel_pch_thermal 16384 0
evdev 28672 39
int3403_thermal 16384 0
int340x_thermal_zone 16384 2 int3403_thermal,processor_thermal_device
wmi 28672 2 hp_wmi,wmi_bmof
hp_wireless 16384 0
i2c_algo_bit 16384 1 i915
int3400_thermal 16384 0
button 16384 0
acpi_thermal_rel 16384 1 int3400_thermal
fan 16384 0
intel_rapl_perf 16384 0
squashfs 65536 1
zstd_decompress 81920 1 squashfs
xxhash 16384 1 zstd_decompress
loop 36864 2
nls_utf8 16384 1
isofs 49152 1
dm_mod 155648 4 dm_crypt
hid_generic 16384 0
usbhid 57344 0
hid 135168 2 usbhid,hid_generic
uas 28672 0
usb_storage 73728 2 uas
sr_mod 28672 0
cdrom 65536 1 sr_mod
sd_mod 61440 3
xhci_pci 16384 0
xhci_hcd 266240 1 xhci_pci
ahci 40960 1
libahci 40960 1 ahci
libata 270336 2 libahci,ahci
scsi_mod 249856 6 sd_mod,usb_storage,uas,libata,sg,sr_mod
mmc_block 49152 0
mmc_core 176128 1 mmc_block
crc32c_generic 16384 0
overlay 131072 1
battery 20480 0
ehci_hcd 94208 0
usbcore 294912 8 xhci_hcd,usbhid,usb_storage,uvcvideo,ehci_hcd,btusb,xhci_pci,uas
usb_common 16384 1 usbcore


Here are lsmod results from linux mint with newer kernel on which adapter is not detected:

Module Size Used by
snd_soc_skl 106496 0
snd_soc_hdac_hda 24576 1 snd_soc_skl
intel_rapl 24576 0
x86_pkg_temp_thermal 20480 0
snd_hda_ext_core 28672 2 snd_soc_hdac_hda,snd_soc_skl
intel_powerclamp 20480 0
snd_soc_skl_ipc 65536 1 snd_soc_skl
coretemp 20480 0
snd_soc_sst_ipc 20480 1 snd_soc_skl_ipc
snd_soc_sst_dsp 36864 1 snd_soc_skl_ipc
snd_soc_acpi_intel_match 28672 1 snd_soc_skl
snd_hda_codec_hdmi 53248 1
kvm_intel 241664 0
snd_soc_acpi 16384 2 snd_soc_acpi_intel_match,snd_soc_skl
snd_soc_core 233472 2 snd_soc_hdac_hda,snd_soc_skl
snd_hda_codec_realtek 114688 1
snd_hda_codec_generic 77824 1 snd_hda_codec_realtek
ledtrig_audio 16384 2 snd_hda_codec_generic,snd_hda_codec_realtek
snd_compress 24576 1 snd_soc_core
ac97_bus 16384 1 snd_soc_core
uvcvideo 94208 0
snd_pcm_dmaengine 16384 1 snd_soc_core
crct10dif_pclmul 16384 1
snd_hda_intel 49152 3
crc32_pclmul 16384 0
videobuf2_vmalloc 20480 1 uvcvideo
videobuf2_memops 20480 1 videobuf2_vmalloc
videobuf2_v4l2 24576 1 uvcvideo
snd_hda_codec 135168 5 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec_realtek,snd_soc_hdac_hda
videobuf2_common 45056 2 videobuf2_v4l2,uvcvideo
ghash_clmulni_intel 16384 0
aesni_intel 372736 0
videodev 204800 3 videobuf2_v4l2,uvcvideo,videobuf2_common
snd_hda_core 86016 8 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel,snd_hda_ext_core,snd_hda_codec,snd_hda_codec_ realtek,snd_soc_hdac_hda,snd_soc_skl
snd_hwdep 20480 1 snd_hda_codec
media 53248 4 videodev,videobuf2_v4l2,uvcvideo,videobuf2_common
snd_pcm 102400 8 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_ext_core,snd_hda_codec,snd_soc_core,snd_soc_skl,snd_hda_cor e,snd_pcm_dmaengine
aes_x86_64 20480 1 aesni_intel
snd_seq_midi 20480 0
crypto_simd 16384 1 aesni_intel
snd_seq_midi_event 16384 1 snd_seq_midi
cryptd 24576 3 crypto_simd,ghash_clmulni_intel,aesni_intel
snd_rawmidi 36864 1 snd_seq_midi
glue_helper 16384 1 aesni_intel
snd_seq 69632 2 snd_seq_midi,snd_seq_midi_event
intel_cstate 20480 0
snd_seq_device 16384 3 snd_seq,snd_seq_midi,snd_rawmidi
hp_wmi 16384 0
intel_rapl_perf 16384 0
joydev 28672 0
input_leds 16384 0
snd_timer 36864 2 snd_seq,snd_pcm
sparse_keymap 16384 1 hp_wmi
serio_raw 20480 0
wmi_bmof 16384 0
intel_wmi_thunderbolt 20480 0
snd 86016 19 snd_hda_codec_generic,snd_seq,snd_seq_device,snd_hda_codec_hdmi,snd_hwdep,snd_hda_intel,snd_hda_code c,snd_hda_codec_realtek,snd_timer,snd_compress,snd_soc_core,snd_pcm,snd_rawmidi
mei_me 40960 0
mei 106496 1 mei_me
soundcore 16384 1 snd
processor_thermal_device 20480 0
int3400_thermal 20480 0
int3403_thermal 16384 0
int340x_thermal_zone 16384 2 int3403_thermal,processor_thermal_device
acpi_thermal_rel 16384 1 int3400_thermal
intel_soc_dts_iosf 20480 1 processor_thermal_device
intel_pch_thermal 16384 0
mac_hid 16384 0
hp_wireless 16384 0
acpi_pad 184320 0
acpi_tad 16384 0
sch_fq_codel 20480 2
parport_pc 36864 0
ppdev 24576 0
lp 20480 0
parport 53248 3 parport_pc,lp,ppdev
ip_tables 32768 0
x_tables 40960 1 ip_tables
autofs4 45056 2
overlay 110592 1
nls_utf8 16384 1
isofs 49152 1
dm_mirror 24576 0
dm_region_hash 20480 1 dm_mirror
dm_log 20480 2 dm_region_hash,dm_mirror
i915 1818624 13
kvmgt 28672 0
vfio_mdev 16384 0
mdev 24576 2 kvmgt,vfio_mdev
vfio_iommu_type1 28672 0
vfio 32768 3 kvmgt,vfio_mdev,vfio_iommu_type1
kvm 630784 2 kvmgt,kvm_intel
hid_generic 16384 0
irqbypass 16384 1 kvm
i2c_algo_bit 16384 1 i915
drm_kms_helper 180224 1 i915
syscopyarea 16384 1 drm_kms_helper
uas 24576 0
sysfillrect 16384 1 drm_kms_helper
sysimgblt 16384 1 drm_kms_helper
fb_sys_fops 16384 1 drm_kms_helper
drm 483328 6 drm_kms_helper,i915
psmouse 151552 0
usbhid 53248 0
r8169 86016 0
ahci 40960 1
hid 126976 2 usbhid,hid_generic
usb_storage 69632 2 uas
realtek 20480 0
libahci 32768 1 ahci
wmi 28672 3 hp_wmi,intel_wmi_thunderbolt,wmi_bmof
video 49152 1 i915


As you can see in Linux Mint with newer kernel, the btusb, btrtl, rfcomm, bluetooth modules are not loaded on startup, but if I manually load them using modprobe commands, they get loaded successfully and here are the results of lsmod after loading the modules manually:

Module Size Used by
rfcomm 77824 0
btusb 49152 0
btrtl 20480 1 btusb
btbcm 16384 1 btusb
btintel 24576 1 btusb
bluetooth 557056 7 btrtl,btintel,btbcm,btusb,rfcomm
ecdh_generic 28672 1 bluetooth
snd_soc_skl 106496 0
snd_soc_hdac_hda 24576 1 snd_soc_skl
intel_rapl 24576 0
x86_pkg_temp_thermal 20480 0
snd_hda_ext_core 28672 2 snd_soc_hdac_hda,snd_soc_skl
intel_powerclamp 20480 0
snd_soc_skl_ipc 65536 1 snd_soc_skl
coretemp 20480 0
snd_soc_sst_ipc 20480 1 snd_soc_skl_ipc
snd_soc_sst_dsp 36864 1 snd_soc_skl_ipc
snd_soc_acpi_intel_match 28672 1 snd_soc_skl
snd_hda_codec_hdmi 53248 1
kvm_intel 241664 0
snd_soc_acpi 16384 2 snd_soc_acpi_intel_match,snd_soc_skl
snd_soc_core 233472 2 snd_soc_hdac_hda,snd_soc_skl
snd_hda_codec_realtek 114688 1
snd_hda_codec_generic 77824 1 snd_hda_codec_realtek
ledtrig_audio 16384 2 snd_hda_codec_generic,snd_hda_codec_realtek
snd_compress 24576 1 snd_soc_core
ac97_bus 16384 1 snd_soc_core
uvcvideo 94208 0
snd_pcm_dmaengine 16384 1 snd_soc_core
crct10dif_pclmul 16384 1
snd_hda_intel 49152 3
crc32_pclmul 16384 0
videobuf2_vmalloc 20480 1 uvcvideo
videobuf2_memops 20480 1 videobuf2_vmalloc
videobuf2_v4l2 24576 1 uvcvideo
snd_hda_codec 135168 5 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec_realtek,snd_soc_hdac_hda
videobuf2_common 45056 2 videobuf2_v4l2,uvcvideo
ghash_clmulni_intel 16384 0
aesni_intel 372736 0
videodev 204800 3 videobuf2_v4l2,uvcvideo,videobuf2_common
snd_hda_core 86016 8 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel,snd_hda_ext_core,snd_hda_codec,snd_hda_codec_ realtek,snd_soc_hdac_hda,snd_soc_skl
snd_hwdep 20480 1 snd_hda_codec
media 53248 4 videodev,videobuf2_v4l2,uvcvideo,videobuf2_common
snd_pcm 102400 8 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_ext_core,snd_hda_codec,snd_soc_core,snd_soc_skl,snd_hda_cor e,snd_pcm_dmaengine
aes_x86_64 20480 1 aesni_intel
snd_seq_midi 20480 0
crypto_simd 16384 1 aesni_intel
snd_seq_midi_event 16384 1 snd_seq_midi
cryptd 24576 3 crypto_simd,ghash_clmulni_intel,aesni_intel
snd_rawmidi 36864 1 snd_seq_midi
glue_helper 16384 1 aesni_intel
snd_seq 69632 2 snd_seq_midi,snd_seq_midi_event
intel_cstate 20480 0
snd_seq_device 16384 3 snd_seq,snd_seq_midi,snd_rawmidi
hp_wmi 16384 0
intel_rapl_perf 16384 0
joydev 28672 0
input_leds 16384 0
snd_timer 36864 2 snd_seq,snd_pcm
sparse_keymap 16384 1 hp_wmi
serio_raw 20480 0
wmi_bmof 16384 0
intel_wmi_thunderbolt 20480 0
snd 86016 19 snd_hda_codec_generic,snd_seq,snd_seq_device,snd_hda_codec_hdmi,snd_hwdep,snd_hda_intel,snd_hda_code c,snd_hda_codec_realtek,snd_timer,snd_compress,snd_soc_core,snd_pcm,snd_rawmidi
mei_me 40960 0
mei 106496 1 mei_me
soundcore 16384 1 snd
processor_thermal_device 20480 0
int3400_thermal 20480 0
int3403_thermal 16384 0
int340x_thermal_zone 16384 2 int3403_thermal,processor_thermal_device
acpi_thermal_rel 16384 1 int3400_thermal
intel_soc_dts_iosf 20480 1 processor_thermal_device
intel_pch_thermal 16384 0
mac_hid 16384 0
hp_wireless 16384 0
acpi_pad 184320 0
acpi_tad 16384 0
sch_fq_codel 20480 2
parport_pc 36864 0
ppdev 24576 0
lp 20480 0
parport 53248 3 parport_pc,lp,ppdev
ip_tables 32768 0
x_tables 40960 1 ip_tables
autofs4 45056 2
overlay 110592 1
nls_utf8 16384 1
isofs 49152 1
dm_mirror 24576 0
dm_region_hash 20480 1 dm_mirror
dm_log 20480 2 dm_region_hash,dm_mirror
i915 1818624 13
kvmgt 28672 0
vfio_mdev 16384 0
mdev 24576 2 kvmgt,vfio_mdev
vfio_iommu_type1 28672 0
vfio 32768 3 kvmgt,vfio_mdev,vfio_iommu_type1
kvm 630784 2 kvmgt,kvm_intel
hid_generic 16384 0
irqbypass 16384 1 kvm
i2c_algo_bit 16384 1 i915
drm_kms_helper 180224 1 i915
syscopyarea 16384 1 drm_kms_helper
uas 24576 0
sysfillrect 16384 1 drm_kms_helper
sysimgblt 16384 1 drm_kms_helper
fb_sys_fops 16384 1 drm_kms_helper
drm 483328 6 drm_kms_helper,i915
psmouse 151552 0
usbhid 53248 0
r8169 86016 0
ahci 40960 1
hid 126976 2 usbhid,hid_generic
usb_storage 69632 2 uas
realtek 20480 0
libahci 32768 1 ahci
wmi 28672 3 hp_wmi,intel_wmi_thunderbolt,wmi_bmof
video 49152 1 i915

does this modprobe helps to find the bluetooth device?
I would look for firmware related message in dmesg or /var/log (if that was tried to use or [something else] ??? )

Here are some steps to diagnose: https://bbs.archlinux.org/viewtopic.php?id=126603&p=2

1. No, modprobe does nothing to enable bluetooth, the adapter is still not detected.
2. That is what I was also looking for in dmesg, but this is the weird thing with newer kernels, I can see that unable to load firmware message in older kernels, but on kernels after 4.19.x, it seems like there is no bluetooth in the laptop and there is not message regarding the adapter in dmesg.

One another thing is that if I use a virtual machine in windows, it is able to detect the adapter and proper firmware loading messages in dmesg log appear for my rtl8723d adapter.

Is this possible that the Windows might be causing some problem?

Something to try:
https://askubuntu.com/questions/1012...-for-chip-id-2
https://askubuntu.com/questions/1033...-for-rtl8723de

and the latest firmware:
https://github.com/wkennington/linux.../master/rtl_bt

Well, nothing is working, I think I should just stick with the distros with 4.19.x kernels. Thanks a lot for the responses!

Here's a similar discussion on your Realtek rtl8723d:
https://askubuntu.com/questions/1170...nux-kernel-5-3