Hi, AFAIK every time a new v4l device is initialized (e.g. USB webcam plugged in) the driver sets the controls to the default value decided by the author in the source code.
It is then the responsibility of each v4l2 applications to save and restore any variation to the controls values made by the user if this is required. I was looking for a more generic way to set some controls to non-default values in a more persistent way, my main use case is to avoid *manually* setting "Power Line Frequency" to 50Hz every time I plug in the webcam. Something like what alsactrl[0] does with mixer settings. Maybe pipewire will do that? In the mean time, inspired by [1] I cleaned up the concept and published it as v4l2-persistent-settings[2], the idea is that the user can save the current state of a device and it would be restored automatically via a udev rule the next time the device is initialized. For that, the current device state has to be stored into a file. For now I am massaging the output of "v4l2-ctl -l", saving that to a file, and then parsing the file to generate something I can pass to "v4l2-ctl --set-ctrl"; however it would be handier if v4l2-ctl had a native mechanism to export and import settings. v4l2ctrl from v4l2ucp[3] has options to save settings to a file and reload them from a file, but I would like to use v4l2-ctl instead which is actively maintained. What about adding such options to v4l2-ctl? Thank you, Antonio [0] http://git.alsa-project.org/?p=alsa-utils.git;a=tree;f=alsactl;hb=HEAD [1] https://superuser.com/questions/471597/linux-v4l-webcam-make-settings-stick [2] https://git.ao2.it/v4l2-persistent-settings.git/ [3] https://sourceforge.net/projects/v4l2ucp/ -- Antonio Ospite https://ao2.it https://twitter.com/ao2it A: Because it messes up the order in which people normally read text. See http://en.wikipedia.org/wiki/Posting_style Q: Why is top-posting such a bad thing?
