Re: pac7302: INFO: possible circular locking dependency detected

[Hans de Goede <hdegoede@xxxxxxxxxx>]

Hi,

I've taken a long time to analyse the below lock dep report, and what can I say,
it is nasty.

This could happen (task could be a thread too):
Task 1: Does a readdir on sysfs
Task 1: Takes sysfs Mutex
Task 2: Does an mmap on the video device
Task 2: Takes mmap semphore
Task 1: Is now stuck waiting for mmap semaphore
Task 3: Does a streamon ioctl on video device
Task 3: Takes queue lock
Task 2: Is now stuck waiting on queue lock
Task 3: Task usb lock
Task 3: Does a usb_set_interface
Task 3: Is now stuck as usb_set_interface wants sysfs mutex

And the is nothing we can do here, as we cannot serialize mmap / ioctl calls at the
level needed (before mmap taking the mmap semaphore).


There are 2 surprising things in here, which together cause the circular problem:

1) A simple readdir on a sysfs dir takes the mmap semaphore
2) A simple usb_set_interface (only changing the alt setting!) takes the sysfs mutex

1 of these 2 is new in 2.6.32 I think otherwise we would have seen this before. So first of
all we should take this discussion to the general kernel mailing list and try to get one
of these 2 fixed.

Alternatively we could move the usb bandwidth negotiation (which does the usb_set_interface)
to device probe time, by pre-allocating the usb bandwidth, but we really don't want to do that,
as that means that in multiple isoc devices configurations only the first cam *probed* will
work (now usually only the first cam started works, which means atleast multiple cams can
be used but not at the same time).

Regards,

Hans

p.s.

About the usb control msg errors, I don't think they are related to this issue at all, no real
world app ever does a streamon and an mmap at the same time. As said if we could serialize mmap and
ioctl at a high enough level, things would be fine too.

Are you seeing this issue on uhci using machines, or is it more general ? Also keep in mind
the pac7302 is a very buggy device. I think we've had this issue (the need to sometimes plug
it in a second time) for as long as we support it.






On 11/06/2009 10:05 PM, Németh Márton wrote:
> Hi,
>
> sometimes when I plug my Labtec Webcam 2200 and then try to start capturing I get
> no picture but some error message in dmesg. I am using 13326:40705fec2fb2 from
> http://linuxtv.org/hg/v4l-dvb/ on top of Linux 2.6.32-rc6.
>
> [ 2282.076229] usb 3-2: new full speed USB device using uhci_hcd and address 2
> [ 2282.314601] usb 3-2: New USB device found, idVendor=093a, idProduct=2626
> [ 2282.314622] usb 3-2: New USB device strings: Mfr=0, Product=0, SerialNumber=0
> [ 2282.317636] usb 3-2: configuration #1 chosen from 1 choice
> [ 2282.562231] Linux video capture interface: v2.00
> [ 2282.599805] gspca: main v2.7.0 registered
> [ 2282.628561] gspca: probing 093a:2626
> [ 2282.629052] usbcore: registered new interface driver snd-usb-audio
> [ 2282.634125] gspca: /dev/video0 created
> [ 2282.634563] usbcore: registered new interface driver pac7302
> [ 2282.634602] pac7302: registered
> [ 2298.627711]
> [ 2298.627715] =======================================================
> [ 2298.627725] [ INFO: possible circular locking dependency detected ]
> [ 2298.627734] 2.6.32-rc6 #1
> [ 2298.627738] -------------------------------------------------------
> [ 2298.627745] svv/3820 is trying to acquire lock:
> [ 2298.627751]  (sysfs_mutex){+.+.+.}, at: [<c110778b>] sysfs_get_dirent+0x15/0x4c
> [ 2298.627773]
> [ 2298.627775] but task is already holding lock:
> [ 2298.627781]  (&gspca_dev->usb_lock){+.+...}, at: [<f81400c2>] gspca_init_transfer+0x20/0x384 [gspca_main]
> [ 2298.627801]
> [ 2298.627803] which lock already depends on the new lock.
> [ 2298.627806]
> [ 2298.627811]
> [ 2298.627813] the existing dependency chain (in reverse order) is:
> [ 2298.627819]
> [ 2298.627821] ->  #3 (&gspca_dev->usb_lock){+.+...}:
> [ 2298.627833]        [<c105da6b>] __lock_acquire+0x10e9/0x13ea
> [ 2298.627846]        [<c105de1f>] lock_acquire+0xb3/0xd0
> [ 2298.627856]        [<c128619c>] mutex_lock_interruptible_nested+0x50/0x37b
> [ 2298.627869]        [<f81400c2>] gspca_init_transfer+0x20/0x384 [gspca_main]
> [ 2298.627883]        [<f81404a3>] vidioc_streamon+0x4a/0x95 [gspca_main]
> [ 2298.627895]        [<f80d1384>] __video_do_ioctl+0x167d/0x3688 [videodev]
> [ 2298.627910]        [<f80d365e>] video_ioctl2+0x2cf/0x371 [videodev]
> [ 2298.627923]        [<f80cf15b>] v4l2_unlocked_ioctl+0x2e/0x32 [videodev]
> [ 2298.627936]        [<c10d20d3>] vfs_ioctl+0x22/0x69
> [ 2298.627947]        [<c10d2642>] do_vfs_ioctl+0x484/0x4be
> [ 2298.627958]        [<c10d26bc>] sys_ioctl+0x40/0x5a
> [ 2298.627969]        [<c10032a4>] sysenter_do_call+0x12/0x38
> [ 2298.627981]
> [ 2298.627983] ->  #2 (&gspca_dev->queue_lock){+.+.+.}:
> [ 2298.627994]        [<c105da6b>] __lock_acquire+0x10e9/0x13ea
> [ 2298.628005]        [<c105de1f>] lock_acquire+0xb3/0xd0
> [ 2298.628015]        [<c128619c>] mutex_lock_interruptible_nested+0x50/0x37b
> [ 2298.628027]        [<f814149d>] dev_mmap+0x5a/0x1c7 [gspca_main]
> [ 2298.628039]        [<f80cf191>] v4l2_mmap+0x32/0x3d [videodev]
> [ 2298.628052]        [<c10b5207>] mmap_region+0x246/0x40b
> [ 2298.628063]        [<c10b566c>] do_mmap_pgoff+0x2a0/0x2f0
> [ 2298.628073]        [<c100704c>] sys_mmap2+0x5a/0x7b
> [ 2298.628083]        [<c10032a4>] sysenter_do_call+0x12/0x38
> [ 2298.628094]
> [ 2298.628096] ->  #1 (&mm->mmap_sem){++++++}:
> [ 2298.628107]        [<c105da6b>] __lock_acquire+0x10e9/0x13ea
> [ 2298.628118]        [<c105de1f>] lock_acquire+0xb3/0xd0
> [ 2298.628128]        [<c10aef03>] might_fault+0x6b/0x88
> [ 2298.628138]        [<c11581ac>] copy_to_user+0x2c/0xfc
> [ 2298.628149]        [<c10d2aab>] filldir64+0x97/0xcd
> [ 2298.628160]        [<c1107691>] sysfs_readdir+0x117/0x14b
> [ 2298.628171]        [<c10d2cbd>] vfs_readdir+0x68/0x94
> [ 2298.628181]        [<c10d2d4c>] sys_getdents64+0x63/0xa0
> [ 2298.628192]        [<c10032a4>] sysenter_do_call+0x12/0x38
> [ 2298.628202]
> [ 2298.628204] ->  #0 (sysfs_mutex){+.+.+.}:
> [ 2298.628215]        [<c105d7f6>] __lock_acquire+0xe74/0x13ea
> [ 2298.628226]        [<c105de1f>] lock_acquire+0xb3/0xd0
> [ 2298.628236]        [<c128688e>] mutex_lock_nested+0x47/0x2c6
> [ 2298.628246]        [<c110778b>] sysfs_get_dirent+0x15/0x4c
> [ 2298.628257]        [<c1108e7a>] sysfs_remove_group+0x1e/0xa3
> [ 2298.628268]        [<c11c8c1c>] dpm_sysfs_remove+0x10/0x12
> [ 2298.628279]        [<c11c41c1>] device_del+0x33/0x131
> [ 2298.628291]        [<c11c42ca>] device_unregister+0xb/0x15
> [ 2298.628301]        [<f84c22a1>] usb_remove_ep_devs+0x15/0x1f [usbcore]
> [ 2298.628338]        [<f84bcbd8>] remove_intf_ep_devs+0x21/0x32 [usbcore]
> [ 2298.628372]        [<f84bda27>] usb_set_interface+0xd9/0x16c [usbcore]
> [ 2298.628406]        [<f8140078>] get_ep+0x145/0x16f [gspca_main]
> [ 2298.628418]        [<f814011c>] gspca_init_transfer+0x7a/0x384 [gspca_main]
> [ 2298.628431]        [<f81404a3>] vidioc_streamon+0x4a/0x95 [gspca_main]
> [ 2298.628443]        [<f80d1384>] __video_do_ioctl+0x167d/0x3688 [videodev]
> [ 2298.628457]        [<f80d365e>] video_ioctl2+0x2cf/0x371 [videodev]
> [ 2298.628470]        [<f80cf15b>] v4l2_unlocked_ioctl+0x2e/0x32 [videodev]
> [ 2298.628482]        [<c10d20d3>] vfs_ioctl+0x22/0x69
> [ 2298.628493]        [<c10d2642>] do_vfs_ioctl+0x484/0x4be
> [ 2298.628504]        [<c10d26bc>] sys_ioctl+0x40/0x5a
> [ 2298.628514]        [<c10032a4>] sysenter_do_call+0x12/0x38
> [ 2298.628525]
> [ 2298.628527] other info that might help us debug this:
> [ 2298.628529]
> [ 2298.628536] 2 locks held by svv/3820:
> [ 2298.628541]  #0:  (&gspca_dev->queue_lock){+.+.+.}, at: [<f814047d>] vidioc_streamon+0x24/0x95 [gspca_main]
> [ 2298.628561]  #1:  (&gspca_dev->usb_lock){+.+...}, at: [<f81400c2>] gspca_init_transfer+0x20/0x384 [gspca_main]
> [ 2298.628581]
> [ 2298.628583] stack backtrace:
> [ 2298.628591] Pid: 3820, comm: svv Not tainted 2.6.32-rc6 #1
> [ 2298.628597] Call Trace:
> [ 2298.628608]  [<c1284b9c>] ? printk+0xf/0x13
> [ 2298.628618]  [<c105c53b>] print_circular_bug+0x90/0x9c
> [ 2298.628628]  [<c105d7f6>] __lock_acquire+0xe74/0x13ea
> [ 2298.628639]  [<c11c8f93>] ? device_pm_remove+0x12/0x33
> [ 2298.628651]  [<c105de1f>] lock_acquire+0xb3/0xd0
> [ 2298.628661]  [<c110778b>] ? sysfs_get_dirent+0x15/0x4c
> [ 2298.628671]  [<c110778b>] ? sysfs_get_dirent+0x15/0x4c
> [ 2298.628682]  [<c128688e>] mutex_lock_nested+0x47/0x2c6
> [ 2298.628692]  [<c110778b>] ? sysfs_get_dirent+0x15/0x4c
> [ 2298.628701]  [<c105ba51>] ? mark_held_locks+0x43/0x5b
> [ 2298.628712]  [<c1285fe8>] ? __mutex_unlock_slowpath+0xf8/0x11a
> [ 2298.628722]  [<c105bcb7>] ? trace_hardirqs_on_caller+0x103/0x124
> [ 2298.628732]  [<c110778b>] sysfs_get_dirent+0x15/0x4c
> [ 2298.628743]  [<c1108e7a>] sysfs_remove_group+0x1e/0xa3
> [ 2298.628753]  [<c11c8c1c>] dpm_sysfs_remove+0x10/0x12
> [ 2298.628763]  [<c11c41c1>] device_del+0x33/0x131
> [ 2298.628773]  [<c11c42ca>] device_unregister+0xb/0x15
> [ 2298.628810]  [<f84c22a1>] usb_remove_ep_devs+0x15/0x1f [usbcore]
> [ 2298.628846]  [<f84bcbd8>] remove_intf_ep_devs+0x21/0x32 [usbcore]
> [ 2298.628881]  [<f84bda27>] usb_set_interface+0xd9/0x16c [usbcore]
> [ 2298.628894]  [<f8140078>] get_ep+0x145/0x16f [gspca_main]
> [ 2298.628906]  [<f81400c2>] ? gspca_init_transfer+0x20/0x384 [gspca_main]
> [ 2298.628919]  [<f814011c>] gspca_init_transfer+0x7a/0x384 [gspca_main]
> [ 2298.628932]  [<f81404a3>] vidioc_streamon+0x4a/0x95 [gspca_main]
> [ 2298.628945]  [<f80d1384>] __video_do_ioctl+0x167d/0x3688 [videodev]
> [ 2298.628957]  [<c105df9b>] ? lock_release_non_nested+0x88/0x239
> [ 2298.628966]  [<c10aeee6>] ? might_fault+0x4e/0x88
> [ 2298.628976]  [<c10aeee6>] ? might_fault+0x4e/0x88
> [ 2298.628985]  [<c10aeee6>] ? might_fault+0x4e/0x88
> [ 2298.628995]  [<c10aef1b>] ? might_fault+0x83/0x88
> [ 2298.629005]  [<c1158099>] ? copy_from_user+0x2a/0x111
> [ 2298.629018]  [<f80d365e>] video_ioctl2+0x2cf/0x371 [videodev]
> [ 2298.629030]  [<c1287b31>] ? _spin_unlock_irqrestore+0x3f/0x68
> [ 2298.629040]  [<c105bcb7>] ? trace_hardirqs_on_caller+0x103/0x124
> [ 2298.629050]  [<c105bce3>] ? trace_hardirqs_on+0xb/0xd
> [ 2298.629063]  [<f80d338f>] ? video_ioctl2+0x0/0x371 [videodev]
> [ 2298.629075]  [<f80cf15b>] v4l2_unlocked_ioctl+0x2e/0x32 [videodev]
> [ 2298.629087]  [<f80cf12d>] ? v4l2_unlocked_ioctl+0x0/0x32 [videodev]
> [ 2298.629098]  [<c10d20d3>] vfs_ioctl+0x22/0x69
> [ 2298.629108]  [<c10d2642>] do_vfs_ioctl+0x484/0x4be
> [ 2298.629119]  [<c10c6de3>] ? vfs_write+0xff/0x13d
> [ 2298.629130]  [<c10d26bc>] sys_ioctl+0x40/0x5a
> [ 2298.629140]  [<c10032a4>] sysenter_do_call+0x12/0x38
> [ 2298.755224] pac7302: reg_w_page(): Failed to write register to index 0x49, value 0x0, error -71
> [ 2298.756412] pac7302: reg_w_page(): Failed to write register to index 0x4a, value 0x0, error -71
> [ 2298.757215] pac7302: reg_w_page(): Failed to write register to index 0x4b, value 0xc0, error -71
> [ 2298.758213] pac7302: reg_w_page(): Failed to write register to index 0x4c, value 0xc0, error -71
> [ 2298.759212] pac7302: reg_w_page(): Failed to write register to index 0x4d, value 0x10, error -71
> [ 2298.760408] pac7302: reg_w_page(): Failed to write register to index 0x4e, value 0x0, error -71
> [ 2298.761356] pac7302: reg_w_page(): Failed to write register to index 0x4f, value 0x0, error -71
> [ 2298.762227] pac7302: reg_w_page(): Failed to write register to index 0x50, value 0x0, error -71
> [ 2298.763213] pac7302: reg_w_page(): Failed to write register to index 0x51, value 0x40, error -71
> [ 2298.764334] pac7302: reg_w_page(): Failed to write register to index 0x52, value 0x0, error -71
> [ 2298.765228] pac7302: reg_w_page(): Failed to write register to index 0x53, value 0x0, error -71
> [ 2298.766214] pac7302: reg_w_page(): Failed to write register to index 0x54, value 0x0, error -71
> [ 2298.767212] pac7302: reg_w_page(): Failed to write register to index 0x55, value 0x0, error -71
> [ 2298.768642] pac7302: reg_w_page(): Failed to write register to index 0x56, value 0x0, error -71
> [ 2298.769216] pac7302: reg_w_page(): Failed to write register to index 0x57, value 0x0, error -71
> [ 2298.770213] pac7302: reg_w_page(): Failed to write register to index 0x58, value 0x0, error -71
> [ 2298.771212] pac7302: reg_w_page(): Failed to write register to index 0x59, value 0x40, error -71
> [ 2298.772764] pac7302: reg_w_page(): Failed to write register to index 0x5a, value 0xff, error -71
> [ 2298.773216] pac7302: reg_w_page(): Failed to write register to index 0x5b, value 0x3, error -71
> [ 2298.774213] pac7302: reg_w_page(): Failed to write register to index 0x5c, value 0x19, error -71
> [ 2298.775212] pac7302: reg_w_page(): Failed to write register to index 0x5d, value 0x0, error -71
> [ 2298.776765] pac7302: reg_w_page(): Failed to write register to index 0x5e, value 0x0, error -71
> [ 2298.777216] pac7302: reg_w_page(): Failed to write register to index 0x5f, value 0x0, error -71
> [ 2298.778213] pac7302: reg_w_page(): Failed to write register to index 0x60, value 0x0, error -71
> [ 2298.779212] pac7302: reg_w_page(): Failed to write register to index 0x61, value 0x0, error -71
> [ 2298.780842] pac7302: reg_w_page(): Failed to write register to index 0x62, value 0x0, error -71
> [ 2298.781218] pac7302: reg_w_page(): Failed to write register to index 0x63, value 0x0, error -71
> [ 2298.782213] pac7302: reg_w_page(): Failed to write register to index 0x64, value 0x0, error -71
> [ 2298.783211] pac7302: reg_w_page(): Failed to write register to index 0x65, value 0x0, error -71
> [ 2298.784756] pac7302: reg_w_page(): Failed to write register to index 0x66, value 0x0, error -71
> [ 2298.785217] pac7302: reg_w_page(): Failed to write register to index 0x67, value 0x0, error -71
> [ 2298.786212] pac7302: reg_w_page(): Failed to write register to index 0x68, value 0x0, error -71
> [ 2298.787212] pac7302: reg_w_page(): Failed to write register to index 0x69, value 0x0, error -71
> [ 2298.788444] pac7302: reg_w_page(): Failed to write register to index 0x6a, value 0x0, error -71
> [ 2298.789216] pac7302: reg_w_page(): Failed to write register to index 0x6b, value 0x0, error -71
> [ 2298.790213] pac7302: reg_w_page(): Failed to write register to index 0x6c, value 0x0, error -71
> [ 2298.791212] pac7302: reg_w_page(): Failed to write register to index 0x6d, value 0xc8, error -71
> [ 2298.792342] pac7302: reg_w_page(): Failed to write register to index 0x6e, value 0xc8, error -71
> [ 2298.793219] pac7302: reg_w_page(): Failed to write register to index 0x6f, value 0xc8, error -71
> [ 2298.794213] pac7302: reg_w_page(): Failed to write register to index 0x70, value 0xc8, error -71
> [ 2298.795212] pac7302: reg_w_page(): Failed to write register to index 0x71, value 0x0, error -71
> [ 2298.796320] pac7302: reg_w_page(): Failed to write register to index 0x72, value 0x0, error -71
> [ 2298.797219] pac7302: reg_w_page(): Failed to write register to index 0x73, value 0x0, error -71
> [ 2298.798213] pac7302: reg_w_page(): Failed to write register to index 0x74, value 0x0, error -71
> [ 2298.799212] pac7302: reg_w_page(): Failed to write register to index 0x75, value 0x0, error -71
> [ 2298.800322] pac7302: reg_w_page(): Failed to write register to index 0x76, value 0x0, error -71
> [ 2298.801217] pac7302: reg_w_page(): Failed to write register to index 0x77, value 0x50, error -71
> [ 2298.802213] pac7302: reg_w_page(): Failed to write register to index 0x78, value 0x8, error -71
> [ 2298.803212] pac7302: reg_w_page(): Failed to write register to index 0x79, value 0x10, error -71
> [ 2298.804339] pac7302: reg_w_page(): Failed to write register to index 0x7a, value 0x24, error -71
> [ 2298.805218] pac7302: reg_w_page(): Failed to write register to index 0x7b, value 0x40, error -71
> [ 2298.806213] pac7302: reg_w_page(): Failed to write register to index 0x7c, value 0x0, error -71
> [ 2298.807212] pac7302: reg_w_page(): Failed to write register to index 0x7d, value 0x0, error -71
> [ 2298.808320] pac7302: reg_w_page(): Failed to write register to index 0x7e, value 0x0, error -71
> [ 2298.809219] pac7302: reg_w_page(): Failed to write register to index 0x7f, value 0x0, error -71
> [ 2298.810213] pac7302: reg_w_page(): Failed to write register to index 0x80, value 0x1, error -71
> [ 2298.811212] pac7302: reg_w_page(): Failed to write register to index 0x81, value 0x0, error -71
> [ 2298.812322] pac7302: reg_w_page(): Failed to write register to index 0x82, value 0x2, error -71
> [ 2298.813219] pac7302: reg_w_page(): Failed to write register to index 0x83, value 0x47, error -71
> [ 2298.814213] pac7302: reg_w_page(): Failed to write register to index 0x84, value 0x0, error -71
> [ 2298.815212] pac7302: reg_w_page(): Failed to write register to index 0x85, value 0x0, error -71
> [ 2298.816342] pac7302: reg_w_page(): Failed to write register to index 0x86, value 0x0, error -71
> [ 2298.817219] pac7302: reg_w_page(): Failed to write register to index 0x87, value 0x0, error -71
> [ 2298.818213] pac7302: reg_w_page(): Failed to write register to index 0x88, value 0x0, error -71
> [ 2298.819212] pac7302: reg_w_page(): Failed to write register to index 0x89, value 0x0, error -71
> [ 2298.820319] pac7302: reg_w_page(): Failed to write register to index 0x8a, value 0x0, error -71
> [ 2298.821217] pac7302: reg_w_page(): Failed to write register to index 0x8b, value 0x0, error -71
> [ 2298.822213] pac7302: reg_w_page(): Failed to write register to index 0x8c, value 0x0, error -71
> [ 2298.823212] pac7302: reg_w_page(): Failed to write register to index 0x8d, value 0x0, error -71
> [ 2298.824214] pac7302: reg_w_page(): Failed to write register to index 0x8e, value 0x0, error -71
> [ 2298.825229] pac7302: reg_w_page(): Failed to write register to index 0x8f, value 0x0, error -71
> [ 2298.826214] pac7302: reg_w_page(): Failed to write register to index 0x90, value 0x0, error -71
> [ 2298.827212] pac7302: reg_w_page(): Failed to write register to index 0x91, value 0x2, error -71
> [ 2298.828213] pac7302: reg_w_page(): Failed to write register to index 0x92, value 0xfa, error -71
> [ 2298.829229] pac7302: reg_w_page(): Failed to write register to index 0x93, value 0x0, error -71
> [ 2298.830214] pac7302: reg_w_page(): Failed to write register to index 0x94, value 0x64, error -71
> [ 2298.831212] pac7302: reg_w_page(): Failed to write register to index 0x95, value 0x5a, error -71
> [ 2298.832214] pac7302: reg_w_page(): Failed to write register to index 0x96, value 0x28, error -71
> [ 2298.833227] pac7302: reg_w_page(): Failed to write register to index 0x97, value 0x0, error -71
> [ 2298.834213] pac7302: reg_w_page(): Failed to write register to index 0x98, value 0x0, error -71
> [ 2298.835211] pac7302: reg_w_buf(): Failed to write registers to index 0x11, error -71
> [ 2298.836214] pac7302: reg_w_buf(): Failed to write registers to index 0xff, error -71
> [ 2298.837225] pac7302: reg_w_buf(): Failed to write registers to index 0x13, error -71
> [ 2298.838213] pac7302: reg_w_buf(): Failed to write registers to index 0x22, error -71
> [ 2298.839212] pac7302: reg_w_buf(): Failed to write registers to index 0x27, error -71
> [ 2298.840213] pac7302: reg_w_buf(): Failed to write registers to index 0x2a, error -71
> [ 2298.841230] pac7302: reg_w_buf(): Failed to write registers to index 0x64, error -71
> [ 2298.842213] pac7302: reg_w_buf(): Failed to write registers to index 0x6e, error -71
> [ 2298.843211] pac7302: reg_w_buf(): Failed to write registers to index 0xff, error -71
> [ 2298.844215] pac7302: reg_w_buf(): Failed to write registers to index 0x78, error -71
> [ 2298.845228] pac7302: reg_w(): Failed to write register to index 0xff, value 0x0, error -71
> [ 2298.846213] pac7302: reg_w(): Failed to write register to index 0xa2, value 0x0, error -71
> [ 2298.847212] pac7302: reg_w(): Failed to write register to index 0xa3, value 0x0, error -71
> [ 2298.848215] pac7302: reg_w(): Failed to write register to index 0xa4, value 0x0, error -71
> [ 2298.849227] pac7302: reg_w(): Failed to write register to index 0xa5, value 0x0, error -71
> [ 2298.850213] pac7302: reg_w(): Failed to write register to index 0xa6, value 0xf, error -71
> [ 2298.851212] pac7302: reg_w(): Failed to write register to index 0xa7, value 0x23, error -71
> [ 2298.852213] pac7302: reg_w(): Failed to write register to index 0xa8, value 0x46, error -71
> [ 2298.853227] pac7302: reg_w(): Failed to write register to index 0xa9, value 0x65, error -71
> [ 2298.854213] pac7302: reg_w(): Failed to write register to index 0xaa, value 0x81, error -71
> [ 2298.855212] pac7302: reg_w(): Failed to write register to index 0xab, value 0x9c, error -71
> [ 2298.856214] pac7302: reg_w(): Failed to write register to index 0xdc, value 0x1, error -71
> [ 2298.857228] pac7302: reg_w(): Failed to write register to index 0xff, value 0x3, error -71
> [ 2298.858213] pac7302: reg_w(): Failed to write register to index 0x11, value 0x1, error -71
> [ 2298.859213] pac7302: reg_w(): Failed to write register to index 0xff, value 0x0, error -71
> [ 2298.860214] pac7302: reg_w(): Failed to write register to index 0xf, value 0x0, error -71
> [ 2298.861228] pac7302: reg_w(): Failed to write register to index 0x10, value 0x7f, error -71
> [ 2298.862213] pac7302: reg_w(): Failed to write register to index 0x11, value 0x0, error -71
> [ 2298.863213] pac7302: reg_w(): Failed to write register to index 0x12, value 0x1, error -71
> [ 2298.864213] pac7302: reg_w(): Failed to write register to index 0x13, value 0x0, error -71
> [ 2298.865226] pac7302: reg_w(): Failed to write register to index 0x14, value 0x0, error -71
> [ 2298.866213] pac7302: reg_w(): Failed to write register to index 0x15, value 0x7, error -71
> [ 2298.867211] pac7302: reg_w(): Failed to write register to index 0x16, value 0xe1, error -71
> [ 2298.868214] pac7302: reg_w(): Failed to write register to index 0x17, value 0x0, error -71
> [ 2298.869227] pac7302: reg_w(): Failed to write register to index 0x18, value 0xbe, error -71
> [ 2298.870213] pac7302: reg_w(): Failed to write register to index 0x19, value 0x7, error -71
> [ 2298.871212] pac7302: reg_w(): Failed to write register to index 0x1a, value 0xe0, error -71
> [ 2298.872262] pac7302: reg_w(): Failed to write register to index 0x1b, value 0x0, error -71
> [ 2298.873219] pac7302: reg_w(): Failed to write register to index 0x1c, value 0x1, error -71
> [ 2298.874213] pac7302: reg_w(): Failed to write register to index 0x1d, value 0x7, error -71
> [ 2298.875212] pac7302: reg_w(): Failed to write register to index 0x1e, value 0xce, error -71
> [ 2298.876332] pac7302: reg_w(): Failed to write register to index 0x1f, value 0x0, error -71
> [ 2298.877219] pac7302: reg_w(): Failed to write register to index 0x20, value 0xb1, error -71
> [ 2298.878213] pac7302: reg_w(): Failed to write register to index 0xdc, value 0x1, error -71
> [ 2298.879212] pac7302: reg_w(): Failed to write register to index 0xff, value 0x3, error -71
> [ 2298.880097] pac7302: reg_w(): Failed to write register to index 0x10, value 0xf, error -71
> [ 2298.881227] pac7302: reg_w(): Failed to write register to index 0x11, value 0x1, error -71
> [ 2298.882213] pac7302: reg_w(): Failed to write register to index 0xff, value 0x3, error -71
> [ 2298.883211] pac7302: reg_w(): Failed to write register to index 0x2, value 0x3, error -71
> [ 2298.884264] pac7302: reg_w(): Failed to write register to index 0x11, value 0x1, error -71
> [ 2298.885218] pac7302: reg_w(): Failed to write register to index 0xff, value 0x3, error -71
> [ 2298.886213] pac7302: reg_w(): Failed to write register to index 0x21, value 0x0, error -71
> [ 2298.887212] pac7302: reg_w(): Failed to write register to index 0x11, value 0x1, error -71
> [ 2298.888333] pac7302: reg_w(): Failed to write register to index 0xff, value 0x1, error -71
> [ 2298.889219] pac7302: reg_w(): Failed to write register to index 0x78, value 0x1, error -71
> [ 2302.944305] pac7302: reg_w(): Failed to write register to index 0xff, value 0x1, error -71
> [ 2302.945984] pac7302: reg_w(): Failed to write register to index 0x78, value 0x0, error -71
> [ 2302.946303] pac7302: reg_w(): Failed to write register to index 0x78, value 0x0, error -71
> [ 2302.950279] gspca: set alt 0 err -71
> [ 2302.951298] pac7302: reg_w(): Failed to write register to index 0xff, value 0x1, error -71
> [ 2302.952903] pac7302: reg_w(): Failed to write register to index 0x78, value 0x40, error -71
>
> If I unplug the device, plug it again and try to start capture it works without problem.
>
> Regars,
>
> 	Márton Németh
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