Add Feature V4L2 Control

* This feature allows you to setup v4l2-ctl parameters before stream starts.
* Modified webcamd accordingly.
* Modified libs/configparser.sh.
* Changed functions get_param configured_cams and check_section

Signed-off-by: Stephan Wendel <me@stephanwe.de>

libs/v4l2_control.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-#### Init Stream library
+#### v4l2 control library
 
 #### webcamd - A webcam Service for multiple Cams and Stream Services.
 ####
@@ -10,7 +10,49 @@
 ####
 #### This File is distributed under GPLv3
 ####
+#### Description: Configure Cam with v4l2-ctl options
+#### ex.: v4l2-ctl -c brightness=100
 
 # Exit upon Errors
 set -e
 
+function v4l2_control {
+    log_msg "V4L2 Control:"
+
+    function main {
+        local device v4l2ctl valueless opt_avail
+        for cam in $(configured_cams); do
+            # get device from cam section
+            device="$(get_param "cam ${cam}" device)"
+            # get v4l2ctl parameters
+            v4l2ctl="$(get_param "cam ${cam}" v4l2ctl)"
+
+            # if not empty do
+            if [ -n "${v4l2ctl}" ]; then
+                # Write configured options to Log
+                log_msg "Device: [cam $cam]"
+                log_msg "Options: ${v4l2ctl}"
+                # Split options to array
+                IFS=',' read -a opt < <(echo "${v4l2ctl}"); unset IFS
+                # loop through options
+                for param in "${opt[@]}"; do
+                    # parameter available for device
+                    # needs || true to prevent script to exit
+                    valueless="$(echo "${param}" | cut -d "=" -f1)"
+                    opt_avail="$(v4l2-ctl -d ${device} -L | \
+                    grep -c ${valueless} || true)"
+                    if [ "$opt_avail" -eq "0" ]; then
+                        log_msg "Parameter '${param}' not available for '${device}'. Skipped."
+                    else
+                        v4l2-ctl -d "${device}" -c "${param}" 2> /dev/null
+                    fi
+                done
+            else
+                log_msg "No parameters set for [cam ${cam}]. Skipped."
+            fi
+        done
+    }
+
+    ### MAIN
+    main
+}