<div dir="ltr">The LTS point releases ship updated kernels for hardware enablement. The process is described here: <a href="https://wiki.ubuntu.com/Kernel/LTSEnablementStack">https://wiki.ubuntu.com/Kernel/LTSEnablementStack</a><div><br></div><div>Generally I'd expect that things that work shouldn't stop working. But I know from experience that that assumption is naive. It's software. Stuff breaks. Also, it's the kernel, and they do strange things sometimes.</div><div><br></div><div>Darcy.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Mar 15, 2016 at 5:03 PM, Khalid Baheyeldin <span dir="ltr"><<a href="mailto:kb@2bits.com" target="_blank">kb@2bits.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Finally got around to the task of reinstalling my laptop, using the<br>
warranty replaced SSD disk from OCZ.<br>
<br>
After installing Kubuntu 14.04, guvcview would not work with the built<br>
in webcam, but another USB webcam (actually a microscope of sorts).<br>
Both would give a black screen (no video).<br>
<br>
The USB webcam is supported by uvc (supposedly).<br>
<br>
usb 2-2: New USB device found, idVendor=1871, idProduct=7670<br>
usb 2-2: New USB device strings: Mfr=2, Product=3, SerialNumber=0<br>
usb 2-2: Product: USB2.0 UVC PC Camera<br>
usb 2-2: Manufacturer: GenesysLogic Technology Co., Ltd.<br>
<br>
<br>
Both were working fine with guvcview on the previous install (Ubuntu<br>
Server 14.04, then KDE Plasma Desktop on top, so should not be much<br>
different).<br>
<br>
A lengthy investigation ensued, using programs like Cheese, vlc,<br>
qtv4l2 test, ...etc. Some of them (e.g. Cheese) would work with the<br>
built in web cam, but not the USB webcam. Others (e.g. vlc) could work<br>
with the USB video, but NOT using the uvcvideo driver (e.g. v4l).<br>
<br>
So there was something with the uvcvideo kernel module for the USB<br>
webcam with an error like this:<br>
<br>
kernel: [ 100.912205] uvcvideo: Failed to query (GET_DEF) UVC control<br>
11 on unit 3: -32 (exp. 1).<br>
<br>
The reason I say uvc was the culprit is that other applications using<br>
other drivers do work.<br>
<br>
Luckily, I have the old disk lying around in the state it was in<br>
before I removed it from the laptop. I probed around, and found that<br>
the new Kubuntu install has a 3.19 kernel, while the old one Ubuntu<br>
Server LTS was 3.13.<br>
<br>
So, I installed the Trusty generic image:<br>
<br>
$ sudo aptitude install linux-image-generic-lts-trusty<br>
<br>
And purged the vivid ones:<br>
<br>
$ sudo aptitude purge linux-generic-lts-vivid<br>
linux-image-generic-lts-vivid linux-image-3.19.0-56-generic<br>
linux-image-3.19.0-25-generic linux-image-extra-3.19.0-25-generic<br>
linux-image-extra-3.19.0-56-generic<br>
<br>
After a reboot, both webcams work fine, as things were before.<br>
<br>
There is still the same error in dmesg, but things work as I want them too.<br>
<br>
So, the big questions are:<br>
<br>
1. Why would something that works stop working in a point release of<br>
the kernel (remember that most devices have drivers written once, and<br>
then not touched at all).<br>
<br>
2. Why would an LTS release install a non-LTS kernel?<br>
--<br>
Khalid M. Baheyeldin<br>
<a href="http://2bits.com" rel="noreferrer" target="_blank">2bits.com</a>, Inc.<br>
Fast Reliable Drupal<br>
Drupal optimization, development, customization and consulting.<br>
Simplicity is prerequisite for reliability. -- Edsger W.Dijkstra<br>
Simplicity is the ultimate sophistication. -- Leonardo da Vinci<br>
For every complex problem, there is an answer that is clear, simple,<br>
and wrong." -- H.L. Mencken<br>
<br>
<br>
_______________________________________________<br>
kwlug-disc mailing list<br>
<a href="mailto:kwlug-disc@kwlug.org">kwlug-disc@kwlug.org</a><br>
<a href="http://kwlug.org/mailman/listinfo/kwlug-disc_kwlug.org" rel="noreferrer" target="_blank">http://kwlug.org/mailman/listinfo/kwlug-disc_kwlug.org</a><br>
<br>
</blockquote></div><br></div>