Bug#941884: bbswitch-dkms: bbswitch is broken

[Celejar]

Package: bbswitch-dkms
Version: 0.8-8
Severity: important

bbswitch seems completely broken on my system. On boot, it loads, and
first reports:

bbswitch: disabling discrete graphics

but immediately follows this with:

bbswitch: Succesfully loaded. Discrete card 0000:08:00.0 is on

# cat /proc/acpi/bbswitch
0000:08:00.0 ON

# tee /proc/acpi/bbswitch <<<OFF
OFF

and syslog shows some sort of stack trace (see attached), and
/proc/acpi/bbswitch remains ON

-- System Information:
Debian Release: bullseye/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.2.0-3-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_WARN, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages bbswitch-dkms depends on:
ii  dkms  2.7.1-4

bbswitch-dkms recommends no packages.

Versions of packages bbswitch-dkms suggests:
pn  bumblebee  <none>

-- no debconf information
-------------- next part --------------
ct  6 22:44:26 lila kernel: [  118.730214] bbswitch: disabling discrete graphics
Oct  6 22:44:26 lila kernel: [  118.744071] ------------[ cut here ]------------
Oct  6 22:44:26 lila kernel: [  118.744072] pci 0000:08:00.0: disabling already-disabled device
Oct  6 22:44:26 lila kernel: [  118.744082] WARNING: CPU: 1 PID: 2205 at drivers/pci/pci.c:1924 pci_disable_device+0x8a/0xa0
Oct  6 22:44:26 lila kernel: [  118.744083] Modules linked in: acpi_call(OE) xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpud
p nft_compat nft_counter nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c nf_tables nfnetlink tun bridge stp llc cpufreq_cons
ervative cpufreq_userspace cpufreq_powersave ipmi_devintf ipmi_msghandler snd_hda_codec_hdmi btusb btrtl btbcm btintel bluetooth drbg ansi_cprng ecdh_
generic ecc rmi_smbus rmi_core binfmt_misc intel_rapl arc4 x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass iwlmvm mac80211 crct
10dif_pclmul crc32_pclmul iTCO_wdt rtsx_pci_ms mei_wdt iTCO_vendor_support i915 memstick snd_hda_codec_realtek iwlwifi watchdog rtsx_pci_sdmmc wmi_bmo
f mmc_core snd_hda_codec_generic ghash_clmulni_intel snd_hda_intel intel_cstate intel_uncore snd_hda_codec xhci_pci e1000e thinkpad_acpi intel_rapl_pe
rf snd_hda_core cfg80211 tpm_tis mei_me xhci_hcd drm_kms_helper nvram snd_hwdep ehci_pci snd_pcm tpm_tis_core joydev i2c_i801 pcspkr
Oct  6 22:44:26 lila kernel: [  118.744106]  snd_timer ledtrig_audio ehci_hcd drm snd ptp rtsx_pci sg intel_pch_thermal usbcore mei pps_core soundcore
 tpm rfkill lpc_ich i2c_algo_bit usb_common mfd_core pcc_cpufreq wmi ac battery rng_core video button parport_pc ppdev lp parport sunrpc bbswitch(OE) 
ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 crc32c_generic dm_crypt dm_mod sd_mod crc32c_intel aesni_intel ahci libahci libata psmouse aes_x86_
64 glue_helper crypto_simd cryptd scsi_mod evdev serio_raw
Oct  6 22:44:26 lila kernel: [  118.744124] CPU: 1 PID: 2205 Comm: tee Tainted: G           OE     5.2.0-3-amd64 #1 Debian 5.2.17-1
Oct  6 22:44:26 lila kernel: [  118.744124] Hardware name: LENOVO 20E2CTO1WW/20E2CTO1WW, BIOS N11ET42W (1.18 ) 09/13/2017
Oct  6 22:44:26 lila kernel: [  118.744127] RIP: 0010:pci_disable_device+0x8a/0xa0
Oct  6 22:44:26 lila kernel: [  118.744128] Code: 48 85 ed 75 07 48 8b ab b0 00 00 00 48 8d bb b0 00 00 00 e8 58 ef 11 00 48 89 ea 48 c7 c7 d0 83 8c 8
2 48 89 c6 e8 50 55 c5 ff <0f> 0b eb 8f 48 89 df e8 ea fe ff ff 80 a3 c1 07 00 00 df 5b 5d c3
Oct  6 22:44:26 lila kernel: [  118.744129] RSP: 0018:ffffb6578343fe58 EFLAGS: 00010282
Oct  6 22:44:26 lila kernel: [  118.744130] RAX: 0000000000000000 RBX: ffff89e783c08000 RCX: 0000000000000000
Oct  6 22:44:26 lila kernel: [  118.744131] RDX: 0000000000000033 RSI: ffffffff8300fb93 RDI: 0000000000000246
Oct  6 22:44:26 lila kernel: [  118.744131] RBP: ffff89e7841c6140 R08: ffffffff8300fb60 R09: 0000000000029940
Oct  6 22:44:26 lila kernel: [  118.744132] R10: 0000004867c2b172 R11: 000000000000089d R12: 00007ffdcf072890
Oct  6 22:44:26 lila kernel: [  118.744133] R13: ffffb6578343ff08 R14: 00007ffdcf072890 R15: 0000000000000000
Oct  6 22:44:26 lila kernel: [  118.744134] FS:  00007fda3f0f0580(0000) GS:ffff89e785e40000(0000) knlGS:0000000000000000
Oct  6 22:44:26 lila kernel: [  118.744135] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Oct  6 22:44:26 lila kernel: [  118.744135] CR2: 00005651db4940f8 CR3: 000000021b9b8001 CR4: 00000000003606e0
Oct  6 22:44:26 lila kernel: [  118.744136] Call Trace:
Oct  6 22:44:26 lila kernel: [  118.744141]  bbswitch_off.cold.5+0xc1/0x1d1 [bbswitch]
Oct  6 22:44:26 lila kernel: [  118.744143]  bbswitch_proc_write+0xaf/0xc6 [bbswitch]
Oct  6 22:44:26 lila kernel: [  118.744146]  proc_reg_write+0x39/0x60
Oct  6 22:44:26 lila kernel: [  118.744148]  vfs_write+0xa5/0x1a0
Oct  6 22:44:26 lila kernel: [  118.744150]  ksys_write+0x59/0xd0