Original version of g920_get_config() contained two kind of actions:

    1. Device specific communication to query/set some parameters
       which requires active communication channel with the device,
       or, put in other way, for the call to be sandwiched between
       hid_device_io_start() and hid_device_io_stop().

    2. Input subsystem specific FF controller initialization which, in
       order to access a valid 'struct hid_input' via
       'hid->inputs.next', requires claimed hidinput which means be
       executed after the call to hid_hw_start() with connect_mask
       containing HID_CONNECT_HIDINPUT.

Location of g920_get_config() can only fulfill requirements for #1 and
not #2, which might result in following backtrace:

[   88.312258] logitech-hidpp-device 0003:046D:C262.0005: HID++ 4.2 device connected.
[   88.320298] BUG: kernel NULL pointer dereference, address: 0000000000000018
[   88.320304] #PF: supervisor read access in kernel mode
[   88.320307] #PF: error_code(0x0000) - not-present page
[   88.320309] PGD 0 P4D 0
[   88.320315] Oops: 0000 [#1] SMP PTI
[   88.320320] CPU: 1 PID: 3080 Comm: systemd-udevd Not tainted 5.4.0-rc1+ #31
[   88.320322] Hardware name: Apple Inc. MacBookPro11,1/Mac-189A3D4F975D5FFC, BIOS 149.0.0.0.0 09/17/2018
[   88.320334] RIP: 0010:hidpp_probe+0x61f/0x948 [hid_logitech_hidpp]
[   88.320338] Code: 81 00 00 48 89 ef e8 f0 d6 ff ff 41 89 c6 85 c0 75 b5 0f b6 44 24 28 48 8b 5d 00 88 44 24 1e 89 44 24 0c 48 8b 83 18 1c 00 00 <48> 8b 48 18 48 8b 83 10 19 00 00 48 8b 40 40 48 89 0c 24 0f b7 80
[   88.320341] RSP: 0018:ffffb0a6824aba68 EFLAGS: 00010246
[   88.320345] RAX: 0000000000000000 RBX: ffff93a50756e000 RCX: 0000000000010408
[   88.320347] RDX: 0000000000000000 RSI: ffff93a51f0ad0a0 RDI: 000000000002d0a0
[   88.320350] RBP: ffff93a50416da28 R08: ffff93a50416da70 R09: ffff93a50416da70
[   88.320352] R10: 000000148ae9e60c R11: 00000000000f1525 R12: ffff93a50756e000
[   88.320354] R13: ffff93a50756f8d0 R14: 0000000000000000 R15: ffff93a50756fc38
[   88.320358] FS:  00007f8d8c1e0940(0000) GS:ffff93a51f080000(0000) knlGS:0000000000000000
[   88.320361] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   88.320363] CR2: 0000000000000018 CR3: 00000003996d8003 CR4: 00000000001606e0
[   88.320366] Call Trace:
[   88.320377]  ? _cond_resched+0x15/0x30
[   88.320387]  ? create_pinctrl+0x2f/0x3c0
[   88.320393]  ? kernfs_link_sibling+0x94/0xe0
[   88.320398]  ? _cond_resched+0x15/0x30
[   88.320402]  ? kernfs_activate+0x5f/0x80
[   88.320406]  ? kernfs_add_one+0xe2/0x130
[   88.320411]  hid_device_probe+0x106/0x170
[   88.320419]  really_probe+0x147/0x3c0
[   88.320424]  driver_probe_device+0xb6/0x100
[   88.320428]  device_driver_attach+0x53/0x60
[   88.320433]  __driver_attach+0x8a/0x150
[   88.320437]  ? device_driver_attach+0x60/0x60
[   88.320440]  bus_for_each_dev+0x78/0xc0
[   88.320445]  bus_add_driver+0x14d/0x1f0
[   88.320450]  driver_register+0x6c/0xc0
[   88.320453]  ? 0xffffffffc0d67000
[   88.320457]  __hid_register_driver+0x4c/0x80
[   88.320464]  do_one_initcall+0x46/0x1f4
[   88.320469]  ? _cond_resched+0x15/0x30
[   88.320474]  ? kmem_cache_alloc_trace+0x162/0x220
[   88.320481]  ? do_init_module+0x23/0x230
[   88.320486]  do_init_module+0x5c/0x230
[   88.320491]  load_module+0x26e1/0x2990
[   88.320502]  ? ima_post_read_file+0xf0/0x100
[   88.320508]  ? __do_sys_finit_module+0xaa/0x110
[   88.320512]  __do_sys_finit_module+0xaa/0x110
[   88.320520]  do_syscall_64+0x5b/0x180
[   88.320525]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   88.320528] RIP: 0033:0x7f8d8d1f01fd
[   88.320532] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 5b 8c 0c 00 f7 d8 64 89 01 48
[   88.320535] RSP: 002b:00007ffefa3bb068 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[   88.320539] RAX: ffffffffffffffda RBX: 000055922040cb40 RCX: 00007f8d8d1f01fd
[   88.320541] RDX: 0000000000000000 RSI: 00007f8d8ce4984d RDI: 0000000000000006
[   88.320543] RBP: 0000000000020000 R08: 0000000000000000 R09: 0000000000000007
[   88.320545] R10: 0000000000000006 R11: 0000000000000246 R12: 00007f8d8ce4984d
[   88.320547] R13: 0000000000000000 R14: 000055922040efc0 R15: 000055922040cb40
[   88.320551] Modules linked in: hid_logitech_hidpp(+) fuse rfcomm ccm xt_CHECKSUM xt_MASQUERADE bridge stp llc nf_nat_tftp nf_conntrack_tftp nf_conntrack_netbios_ns nf_conntrack_broadcast xt_CT ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack ebtable_nat ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat tun iptable_mangle iptable_raw iptable_security nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c ip_set nfnetlink ebtable_filter ebtables ip6table_filter ip6_tables cmac bnep sunrpc dm_crypt nls_utf8 hfsplus intel_rapl_msr intel_rapl_common ath9k_htc ath9k_common x86_pkg_temp_thermal intel_powerclamp b43 ath9k_hw coretemp snd_hda_codec_hdmi cordic kvm_intel snd_hda_codec_cirrus mac80211 snd_hda_codec_generic ledtrig_audio kvm snd_hda_intel snd_intel_nhlt irqbypass snd_hda_codec btusb btrtl snd_hda_core ath btbcm ssb snd_hwdep btintel snd_seq crct10dif_pclmul iTCO_wdt snd_seq_device crc32_pclmul bluetooth mmc_core iTCO_vendor_support joydev cfg80211
[   88.320602]  applesmc ghash_clmulni_intel ecdh_generic snd_pcm input_polldev intel_cstate ecc intel_uncore thunderbolt snd_timer i2c_i801 libarc4 rfkill intel_rapl_perf lpc_ich mei_me pcspkr bcm5974 snd bcma mei soundcore acpi_als sbs kfifo_buf sbshc industrialio apple_bl i915 i2c_algo_bit drm_kms_helper drm uas crc32c_intel usb_storage video hid_apple
[   88.320630] CR2: 0000000000000018
[   88.320633] ---[ end trace 933491c8a4fadeb7 ]---
[   88.320642] RIP: 0010:hidpp_probe+0x61f/0x948 [hid_logitech_hidpp]
[   88.320645] Code: 81 00 00 48 89 ef e8 f0 d6 ff ff 41 89 c6 85 c0 75 b5 0f b6 44 24 28 48 8b 5d 00 88 44 24 1e 89 44 24 0c 48 8b 83 18 1c 00 00 <48> 8b 48 18 48 8b 83 10 19 00 00 48 8b 40 40 48 89 0c 24 0f b7 80
[   88.320647] RSP: 0018:ffffb0a6824aba68 EFLAGS: 00010246
[   88.320650] RAX: 0000000000000000 RBX: ffff93a50756e000 RCX: 0000000000010408
[   88.320652] RDX: 0000000000000000 RSI: ffff93a51f0ad0a0 RDI: 000000000002d0a0
[   88.320655] RBP: ffff93a50416da28 R08: ffff93a50416da70 R09: ffff93a50416da70
[   88.320657] R10: 000000148ae9e60c R11: 00000000000f1525 R12: ffff93a50756e000
[   88.320659] R13: ffff93a50756f8d0 R14: 0000000000000000 R15: ffff93a50756fc38
[   88.320662] FS:  00007f8d8c1e0940(0000) GS:ffff93a51f080000(0000) knlGS:0000000000000000
[   88.320664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   88.320667] CR2: 0000000000000018 CR3: 00000003996d8003 CR4: 00000000001606e0

To solve this issue:

   1. Split g920_get_config() such that all of the device specific
      communication remains a part of the function and input subsystem
      initialization bits go to hidpp_ff_init()

   2. Move call to hidpp_ff_init() from being a part of
      g920_get_config() to be the last step of .probe(), right after a
      call to hid_hw_start() with connect_mask containing
      HID_CONNECT_HIDINPUT.

Fixes: 91cf9a98 ("HID: logitech-hidpp: make .probe usbhid capable")
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Tested-by: Sam Bazley <sambazley@fastmail.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Henrik Rydberg <rydberg@bitmath.org>
Cc: Pierre-Loup A. Griffais <pgriffais@valvesoftware.com>
Cc: Austin Palmer <austinp@valvesoftware.com>
Cc: linux-input@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # 5.2+
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>