Why only 8 devices max?

[iwuvjhdva]

Hey, found this line while observing the code:

define MAX_DEVICES 8

We actually need at least 100 devices for our project - is there any workaround for that besides forking?

Thank you!

[gfto]

Just change the define and recompile, it's that simple.

[allegfede]

sorry .. but .. LOL :D

On Wed, Feb 26, 2014 at 11:15 AM, Georgi Chorbadzhiyski <
notifications@github.com> wrote:

Just change the define and recompile, it's that simple.

Reply to this email directly or view it on GitHubhttps://github.com//issues/55#issuecomment-36110365
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[umlaeute]

i've just made MAX_DEVICES (and friends) settable during the build-process, so you don't have to change the define in the source-code.

instead you can just do:

make KCPPFLAGS="-DMAX_DEVICES=100"

[iwuvjhdva]

Thank you for the arranging the setting and for the amazing software!

[cetinakat]

Hello, I used to v4l2loopback for android emulators and it works with great till 100 cameras but when I run "emulator -webcam-list" it just show 8 cameras. Are there any ideas why is that?

Emulator webcam list: http://prntscr.com/j7sgsm
device list: http://prntscr.com/j7shzd

[umlaeute]

@cetinakat so you have 100 working v4l2loopback devices, and some application only shows only a subset and you suspect that the problem is with the 100 devices? have you checked whether your emulator allows more than 8 cameras?

[karllacr]

Hi,
I am facing this problem and I did use all the recommendations, but i didn't have success.
By "all the recommendations" I mean: change the code and recompile, and add make KCPPFLAGS="-DMAX_DEVICES=100" during the build-process

dmesg | grep -i v4l2loopback
[ 5.984450] v4l2loopback: loading out-of-tree module taints kernel.
[ 5.984467] v4l2loopback: module verification failed: signature and/or required key missing - tainting kernel
[ 5.984638] v4l2loopback driver version 0.9.1 loaded
[ 652.694912] v4l2loopback: number of devices is limited to: 8
[ 652.695210] v4l2loopback driver version 0.9.1 loaded

uname -a
4.15.0-47-generic #50~16.04.1-Ubuntu SMP Fri Mar 15 16:06:21 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

lsb_release -a
LSB Version: core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
Distributor ID: Ubuntu
Description: Ubuntu 16.04.5 LTS
Release: 16.04
Codename: xenial

When I run:

modprobe v4l2loopback devices=100

It just create 8 devices... If anyone can help, I would be very grateful :)

[umlaeute]

@karllacr most likely you have conflicting installations of the module and your kernel picks the wrong one.

• did you "install" the newly compiled module
• did you uninstall any leftovers of old compilations of the module

also note that running make after compilation (e.g. with other build targets like make install or make modprobe), might recompile the module if you don't add the KCPPFLAGS="-DMAX_DEVICES=100" (or whatever flags you added) to the build process again.
to be save, pass the flags to all invocations of make.

[karllacr]

@umlaeute I did as you recommended and it worked!
Thank you :D