Discussion:
Experience with the v4l backend?
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d***@mail.com
2017-03-17 11:56:07 UTC
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On 02/04/2017(Sat) 07:10
Subject: Re: [sane-devel] Experience with the v4l backend?
I can't take a gray scale image with my usb cam either.
I'd guess that this is a bug.
Possibly, yes.
I fact, I can only take one image and then the second generates an
error.
Ok, that is a bug. The question is if it is a bug with sane or with
the device itself.
Sorry, catching up with my mail.
Does the device (usb cam) worh with other programs after taking an
image with sane first?
I'm not sure, now I can't scan at all via the v4l.
I just tried, scanimage reported an I/O error, and the kernel has spat
out a bunch of info:

Mar 15 03:02:01 [kernel] [1165605.488904] uvcvideo: Failed to query (131)
UVC probe control : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.493100] uvcvideo: Failed to set UVC
probe control : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.500103] uvcvideo: Failed to set
UVC probe control : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.504359] uvcvideo: Failed to set UVC
probe cont rol : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.508605] uvcvideo: Failed to set
UVC probe control : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.512880] uvcvideo: Failed to set UVC
probe control : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.517106] uvcvideo: Failed to query
(GET_CUR) UVC control 6 on unit 2: -71 (exp. 2).
Mar 15 03:02:01 [kernel] [1165605.521358] uvcvideo: Failed to query
(SET_CUR) UVC control 2 on unit 2: -71 (exp. 2).
Mar 15 03:02:01 [kernel] [1165605.525609] uvcvideo:
Failed to query (SET_CUR) UVC control 6 on unit 2: -71 (exp. 2).
Mar 15 03:02:01 [kernel] [1165605.529862] uvcvideo: Failed to query
(SET_CUR) UVC control 3 on unit 2: -71 (exp. 2).
Mar 15 03:02:01 [kernel] [1165605.534104] uvcvideo: Failed to query
(SET_CUR) UVC control 7 on unit 2: -71 (exp. 2).
Mar 15 03:02:01 [kernel] [1165605.538355] uvcvideo:
Failed to query (SET_CUR) UVC control 9 on unit 2: -71 (exp. 2).
Mar 15 03:02:01 [kernel] [1165605.542611] uvcvideo: Failed to set UVC
probe control : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.546853] uvcvideo: Failed to set UVC
probe control : -71 (exp. 26).
Mar 15 03:02:01 [kernel] [1165605.577255] usb 3-1.3: USB disconnect,
device number 82

Now /dev/video0 has vanished and sane reports no v4l.

It could really be the cam, most of this laptop has broken (and only
after 2 years ):

It's not a huge issue for me, I hardly used it anyway.

Thanks,
David
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