maintainer-feedback requested: [Bug 252327] multimedia/v4l-utils: v4l2-ctl can't determine the device type

[bugzilla-noreply at freebsd.org]

Bugzilla Automation <bugzilla at FreeBSD.org> has asked freebsd-multimedia
(Nobody) <multimedia at FreeBSD.org> for maintainer-feedback:
Bug 252327: multimedia/v4l-utils: v4l2-ctl can't determine the device type
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252327



--- Description ---
v4l2-ctl allows you to set options on a web camera. For example, changing the
power line frequency to 50 Hz to get rid of flicker with lights in Europe.

Unfortunately, it seems that v4l2-ctl can't determine the device type. Running
it with any sort of webcam produces the following:

v4l2-ctl -L
Unable to detect what device /dev/video0 is, exiting.

Looking at the source code it seems that mi_media_detect_type() in
media-info.cpp is using the Linux sysfs and uevent to get information about the
device type. This information doesn't exist on FreeBSD (at least not in that
form).

If one hardcodes(!) the type to MEDIA_TYPE_VIDEO, the information does show up:

./v4l2-ctl -L
		     brightness 0x00980900 (int)    : min=0 max=255 step=1
default=128 value=128
		       contrast 0x00980901 (int)    : min=0 max=255 step=1
default=128 value=128
		     saturation 0x00980902 (int)    : min=0 max=255 step=1
default=128 value=128
 white_balance_temperature_auto 0x0098090c (bool)   : default=1 value=1
			   gain 0x00980913 (int)    : min=0 max=255 step=1
default=0 value=136
	   power_line_frequency 0x00980918 (menu)   : min=0 max=2 default=2
value=1
				0: Disabled
				1: 50 Hz
				2: 60 Hz
      white_balance_temperature 0x0098091a (int)    : min=2000 max=6500 step=1
default=4000 value=3385 flags=inactive
		      sharpness 0x0098091b (int)    : min=0 max=255 step=1
default=128 value=128
	 backlight_compensation 0x0098091c (int)    : min=0 max=1 step=1
default=0 value=0
		  exposure_auto 0x009a0901 (menu)   : min=0 max=3 default=3
value=3
				1: Manual Mode
				3: Aperture Priority Mode
	      exposure_absolute 0x009a0902 (int)    : min=3 max=2047 step=1
default=250 value=299 flags=inactive
	 exposure_auto_priority 0x009a0903 (bool)   : default=0 value=1
		   pan_absolute 0x009a0908 (int)    : min=-36000 max=36000
step=3600 default=0 value=0
		  tilt_absolute 0x009a0909 (int)    : min=-36000 max=36000
step=3600 default=0 value=0
		 focus_absolute 0x009a090a (int)    : min=0 max=250 step=5
default=0 value=50 flags=inactive
		     focus_auto 0x009a090c (bool)   : default=1 value=1
		  zoom_absolute 0x009a090d (int)    : min=100 max=500 step=1
default=100 value=100


Naturally, hard coding this value is not a permanent solution, but it does show
that things work afterwards. There are still issues in setting values
(getsubopt returns differently), but the first step is to get the items to
recognize correctly.