Hi,

Please check the attached patch proposal for drivers/bluetooth/btusb.c
0.8.1 (for 5.3-rc6/rc8 kernels).

I haven't tested it thoroughly but I can get sound with these changes
on my "Cambridge Silicon Radio, Ltd Bluetooth Dongle" adapters
(ATTRS{idVendor}=="0a12", ATTRS{idProduct}=="0001",
ATTRS{bcdDevice}=="8891").

Also, the added kernel module parameters should allow easier testing
of the available fixups allowing them to be turned on/off via modprobe
(and keep traditional behavior wen not used).

 * Changes: Patching for Cambridge Silicon Radio, Ltd Bluetooth Dongle(HCI mode)
 *          Adapting patches for HCI_QUIRK_BROKEN_STORED_LINK_KEY
 *              based on patch by Szymon Janc <szymon.janc@codecoup.pl>
 *              https://pastebin.com/dHepfTmR
 *          Adding patch for CSR bcdDevice == 0x8891 by Sergey Kondakov from
 *                https://bugzilla.kernel.org/show_bug.cgi?id=60824#c37
 *          Minor Changes allowing some fixups/quirks to be tested and
 *          enabled/disabled via kernel module options:
 *              debug;
 *              disable_csrfix,     force_csrfix;
 *              disable_fakecsr,    force_fakecsr;
 *              disable_npsetup,    force_npsetup;
 *              disable_sniffer,    force_sniffer;
 *              disable_intelboot,  force_intelboot;
 *              disable_scofix,     force_scofix;
 *              disable_slkfix,     force_slkfix;
 *              disable_rocfix,     force_rocfix;
 *              disable_noisoc,     force_noisoc;
 *              disable_ath3012,    force_ath3012;
 *              disable_digianswer, force_digianswer;
 *              disable_intel,      force_intel;
 *              disable_intelnew,   force_intelnew;
 *              disable_marvel,     force_marvel;
 *              disable_mediatek,   force_mediatek;
 *              disable_qcarome,    force_qcarome;
 *              disable_bcm92035,   force_bcm92035;
 *              disable_swave,      force_swave;

Regards.

# Fernando Pires de Carvalho
# pires.carvalho@gmail.com