我的 Logitech C270 网络摄像头无法再在我的桌面上使用，大概是升级到 Ubuntu 18.04 之后发生的。
我在下面列出了我的一些系统信息和日志。有人可以提供任何建议吗？谢谢！
系统信息
运行 Ubuntu 18.04 LTS。
内核信息：
$ uname -r
4.15.0-88-lowlatency
只有一个视频设备：
$ ls /dev/video*
/dev/video0
检测到网络摄像头：
$ lsusb | grep Logitech
Bus 003 Device 007: ID 046d:0825 Logitech, Inc. Webcam C270
$ sudo lshw | grep Logitech -B3 -A6
*-usb:2
description: Video
product: Webcam C270
vendor: Logitech, Inc.
physical id: 9
bus info: usb@3:9
version: 0.12
serial: E4E41130
capabilities: usb-2.00
configuration: driver=snd-usb-audio maxpower=500mA speed=480Mbit/s
网络摄像头目前插入 USB 2.0 端口，因为我看到资料说它不适用于 USB 3.0。
尝试使用网络摄像头
我尝试使用guvcview和cheese；两者似乎都尝试使用网络摄像头（开启/dev/video0），因为网络摄像头上的绿灯亮起，但没有视频输出。
运行guvcview没有视频输出，并且打印以下日志：
$ guvcview
GUVCVIEW: version 2.0.5
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
(guvcview:22416): Gtk-WARNING **: 22:19:05.714: GTK+ module libgail.so cannot be loaded.
GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported.
Gtk-Message: 22:19:05.714: Not loading module "atk-bridge": The functionality is provided by GTK natively. Please try to not load it.
V4L2_CORE: Could not grab image (select timeout): Directory not empty
V4L2_CORE: Could not grab image (select timeout): Directory not empty
V4L2_CORE: Could not grab image (select timeout): Directory not empty
V4L2_CORE: Could not grab image (select timeout): Directory not empty
sudo guvcview也没有显示任何输出，只有以下日志：
$ sudo guvcview
GUVCVIEW: version 2.0.5
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
V4L2_CORE: (UVCIOC_CTRL_MAP) Error: No such file or directory
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
(guvcview:10623): IBUS-WARNING **: 22:21:59.845: The owner of /home/username/.config/ibus/bus is not root!
V4L2_CORE: Could not grab image (select timeout): Resource temporarily unavailable
V4L2_CORE: Could not grab image (select timeout): Resource temporarily unavailable
V4L2_CORE: Could not grab image (select timeout): Resource temporarily unavailable
V4L2_CORE: Could not grab image (select timeout): Resource temporarily unavailable
V4L2_CORE: Could not grab image (select timeout): Resource temporarily unavailable
dmesg输出，最后我尝试了不同的 USB 端口：
$ dmesg | grep -i -e cam -e video
[ 0.054065] ACPI: Added _OSI(Linux-Dell-Video)
[ 0.107416] pci 0000:01:00.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff]
[ 4.873470] Linux video capture interface: v2.00
[ 4.884978] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825)
[ 4.977454] uvcvideo 3-9.3:1.0: Entity type for entity Extension 4 was not initialized!
[ 4.977455] uvcvideo 3-9.3:1.0: Entity type for entity Extension 6 was not initialized!
[ 4.977455] uvcvideo 3-9.3:1.0: Entity type for entity Extension 7 was not initialized!
[ 4.977456] uvcvideo 3-9.3:1.0: Entity type for entity Processing 2 was not initialized!
[ 4.977457] uvcvideo 3-9.3:1.0: Entity type for entity Extension 3 was not initialized!
[ 4.977457] uvcvideo 3-9.3:1.0: Entity type for entity Camera 1 was not initialized!
[ 4.977511] input: UVC Camera (046d:0825) as /devices/pci0000:00/0000:00:14.0/usb3/3-9/3-9.3/3-9.3:1.0/input/input17
[ 4.977579] usbcore: registered new interface driver uvcvideo
[ 4.977580] USB Video Class driver (1.1.1)
[ 331.230142] uvcvideo: Failed to query (SET_CUR) UVC control 10 on unit 2: -32 (exp. 2).
[ 331.398836] uvcvideo: Failed to query (SET_CUR) UVC control 10 on unit 2: -32 (exp. 2).
[ 331.555247] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 331.563479] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 342.858579] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 342.858593] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 364.131263] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 364.131266] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 473.928780] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 473.928784] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 537.498208] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 537.498212] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 544.499587] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 544.499591] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 563.761048] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 563.761052] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 1776.868595] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 1776.868598] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 1786.506681] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 1786.506686] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 1830.042444] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 1830.042450] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 1872.183174] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 1872.183178] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 1998.396169] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 1998.396174] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 2004.517466] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 2004.517471] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 2031.841384] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 2031.841389] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 2282.671235] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 2282.671239] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 2324.197277] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 2324.197282] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 2456.664933] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 2456.664938] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 2534.645562] uvcvideo: Failed to query (SET_CUR) UVC control 4 on unit 1: -32 (exp. 4).
[ 2534.645567] uvcvideo 3-9.3:1.0: reset_resume error -5
[ 2871.852239] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825)
[ 2871.942491] uvcvideo 3-12:1.0: Entity type for entity Extension 4 was not initialized!
[ 2871.942492] uvcvideo 3-12:1.0: Entity type for entity Extension 6 was not initialized!
[ 2871.942493] uvcvideo 3-12:1.0: Entity type for entity Extension 7 was not initialized!
[ 2871.942494] uvcvideo 3-12:1.0: Entity type for entity Processing 2 was not initialized!
[ 2871.942495] uvcvideo 3-12:1.0: Entity type for entity Extension 3 was not initialized!
[ 2871.942496] uvcvideo 3-12:1.0: Entity type for entity Camera 1 was not initialized!
[ 2871.942562] input: UVC Camera (046d:0825) as /devices/pci0000:00/0000:00:14.0/usb3/3-12/3-12:1.0/input/input18
[ 2943.502825] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825)
[ 2943.593046] uvcvideo 3-4:1.0: Entity type for entity Extension 4 was not initialized!
[ 2943.593048] uvcvideo 3-4:1.0: Entity type for entity Extension 6 was not initialized!
[ 2943.593048] uvcvideo 3-4:1.0: Entity type for entity Extension 7 was not initialized!
[ 2943.593049] uvcvideo 3-4:1.0: Entity type for entity Processing 2 was not initialized!
[ 2943.593050] uvcvideo 3-4:1.0: Entity type for entity Extension 3 was not initialized!
[ 2943.593050] uvcvideo 3-4:1.0: Entity type for entity Camera 1 was not initialized!
[ 2943.593156] input: UVC Camera (046d:0825) as /devices/pci0000:00/0000:00:14.0/usb3/3-4/3-4:1.0/input/input19
[ 3022.273264] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825)
[ 3022.363398] uvcvideo 3-9:1.0: Entity type for entity Extension 4 was not initialized!
[ 3022.363400] uvcvideo 3-9:1.0: Entity type for entity Extension 6 was not initialized!
[ 3022.363401] uvcvideo 3-9:1.0: Entity type for entity Extension 7 was not initialized!
[ 3022.363401] uvcvideo 3-9:1.0: Entity type for entity Processing 2 was not initialized!
[ 3022.363402] uvcvideo 3-9:1.0: Entity type for entity Extension 3 was not initialized!
[ 3022.363403] uvcvideo 3-9:1.0: Entity type for entity Camera 1 was not initialized!
[ 3022.363484] input: UVC Camera (046d:0825) as /devices/pci0000:00/0000:00:14.0/usb3/3-9/3-9:1.0/input/input22
[ 3490.979094] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825)
[ 3491.069227] uvcvideo 3-9:1.0: Entity type for entity Extension 4 was not initialized!
[ 3491.069238] uvcvideo 3-9:1.0: Entity type for entity Extension 6 was not initialized!
[ 3491.069239] uvcvideo 3-9:1.0: Entity type for entity Extension 7 was not initialized!
[ 3491.069240] uvcvideo 3-9:1.0: Entity type for entity Processing 2 was not initialized!
[ 3491.069240] uvcvideo 3-9:1.0: Entity type for entity Extension 3 was not initialized!
[ 3491.069241] uvcvideo 3-9:1.0: Entity type for entity Camera 1 was not initialized!
[ 3491.069316] input: UVC Camera (046d:0825) as /devices/pci0000:00/0000:00:14.0/usb3/3-9/3-9:1.0/input/input23