Re: Question about rtl8761b Realtek bluetooth dongle firmware

[Zamir SUN <sztsian@gmail.com>]

On 8/4/20 10:14 PM, Jeremy MJ wrote:
> Hi,
> 
> I have reached out to realtek to inquire about licensing and
> permissibility of inclusion of the firmware to linux-firmware, will
> update if / when I hear back.
> 

Hi Jeremy,

Thanks for the reply. Just fyi, I've ever send email to the latest 
Realtek btrtl submitter of linux-firmware (hildawu@), but I did not get 
any reply till now.

I can share where the firmware stays in the Windows driver, but I'm 
reluctant because I don't know if it is proper to share it publicly. 
Getting confirmation from the Realtek engineers is definitely preferred.

> This came up with another user on the Mint forums, who has a specific
> brand using this chipset which provides beta Linux drivers and
> firmware:
> https://forums.linuxmint.com/viewtopic.php?f=49&t=319260&e=1
> 

Well, I cannot read the thread. Looks like account needed and register 
requires a really complex password.. That said, I will try again to read 
it later.

> I have tested both the driver and the firmware in linux 5.8; both
> appear to mostly work (a couple of unexpected event for opcode errors
> with the bluetooth module when using the firmware).
> 

The driver itself got merged in kernel 5.8. And to be a little verbose, 
I'm not sure if distribution packaging (rpm/deb etc.) will try to detect 
the firmware automatically so I did *not* add a MODULE_FIRMWARE line in 
the patch. That shouldn't affect the user as I can listen to music using 
the 5.8 kernel without any hack to the driver (if copying the firmware 
is not called a hack).

The only error I see is the "command 0x2038 tx timeout". And I do 
realize that there are compatible issues (the adapter + firmware can 
only pare with my newest headset, not the ones that I bought over 3 
years ago). Not sure if it is a driver issue or my userspace problems.

The config error is benign. This do not require a config binary.

[  544.152212] Bluetooth: hci0: RTL: examining hci_ver=0a hci_rev=000b 
lmp_ver=0a lmp_subver=8761
[  544.153186] Bluetooth: hci0: RTL: rom_version status=0 version=1
[  544.153190] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761b_fw.bin
[  544.153337] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761b_config.bin
[  544.153366] bluetooth hci0: Direct firmware load for 
rtl_bt/rtl8761b_config.bin failed with error -2
[  544.153372] Bluetooth: hci0: RTL: cfg_sz -2, total sz 18788
[  544.260240] Bluetooth: hci0: RTL: fw version 0xd898c37c
[  546.382558] Bluetooth: hci0: command 0x2038 tx timeout
[  595.434875] Bluetooth: hci0: Ignoring error of Inquiry Cancel command
[  844.482285] debugfs: File 'force_bredr_smp' in directory 'hci0' 
already present!
[  846.539979] Bluetooth: hci0: command 0x2038 tx timeout


> Thank you Zamir for your work on the initial device recognition issue.
> Would be nice to have broader support of bt5 dongles in Linux.
> 

Thanks again for bringing this up. And let's wish hardware vendors can 
do more good to Linux community in the future.

> Regards,
> 
> --
> Jeremy MountainJohnson
> jskier@gmail.com
> 
> ----
> From: Zamir SUN <sztsian@gmail.com>
> To: linux-firmware@kernel.org
> Cc: sztsian@gmail.com
> Subject: Question about rtl8761b Realtek bluetooth dongle firmware
> Date: Fri, 10 Apr 2020 23:44:49 +0800
> Message-ID: <4bb6d05c-b6b6-f8c8-3a49-f76cd129c665@gmail.com> (raw)
> 
> Hi,
> 
> Recently I purchased a unbranded USB Bluetooth dongle which is found not
> supported by Linux yet. And the vendor declare it to have rtl8716b chip.
> After playing with it for a while we've figured out that it's mostly
> compatible with the btrtl driver, with the difference firmware needed.
> We found the firmware from the Windows driver CD shipped along with the
> dongle and confirmed it works in Linux. I've carefully checked the
> Windows driver as well as the installer and did not see any EULA. As I
> don't work for Realtek, neither the producer of this USB dongle, so I am
> writing to ask if I can submit to linux-firmware?
> 
> The patch to the driver is already sent out
> https://patchwork.kernel.org/patch/11483367/
> 
> Thanks in advance.
> 

-- 
Zamir SUN
Fedora user
GPG : 1D86 6D4A 49CE 4BBD 72CF FCF5 D856 6E11 F2A0 525E