System Launch and Monitor (slm)

Updated: April 19, 2023

Use slm in the Sensor Framework for QNX SDP to modify the launch order of applications and services without rebuilding the target image.

For more information about how to use SLM, see slm in the Utilities Reference.

SLM configuration files for Sensor Framework

The Sensor Framework uses multiple SLM configuration files to manage dependencies between processes, commands for launching processes, and other properties.

The following default files are included:

slm-config-all.xml
Configures services common to all hardware platforms.
slm-config-platform.xml
Configures platform-specific services, such as board-specific drivers.
A simple way to switch default SLM configuration files is to copy your custom SLM configuration file to slm-config-platform.xml on your target. For example: 
% mount -uw /base
% cp /base/etc/my-slm-config.xml /base/etc/slm-config-platform.xml
where my-slm-config.xml is the name of the SLM configuration file that you want to use.

Example: SLM configuration to use file camera immediately

Updated: April 19, 2023

This example describes how to set up a SLM file to use a file camera immediately after the target boots.

To use this configuration, you must ensure that you have a file camera specified in the sensor configuration file. For example: 

...
begin SENSOR_UNIT_1
    type = file_camera
    address = /usr/share/videos/adas_example.mp4
    playback_group = 1
    name = front-camera
    direction = 0,0,0
    position = 0,0,800
end SENSOR_UNIT_1
...

For more information, see the “Example: Sensor configuration file for file camera” section.

To configure your SLM configuration file for a file camera, here's what you need to do:

  • Ensure that the resource arbitrator is running before starting the Sensor service (sensor).

    The resarb component must start before the sensor component. The resarb component is used to permit arbitration of resources so that multiple processes can access the same resource. The sensor component requires this arbitration as a dependency when you're using file cameras.

    In general, the resarb component must be started, but it's not required as an explicit dependency for the sensor component for other sensors and cameras.

  • Ensure that the Sensor service has a dependency on Screen.

    For example, start the sensor component with a dependency to wait until the screen_ready component comes up.

  • Start your file camera application.

Your SLM configuration should include components as follows: 

<SLM:system xmlns:SLM="SLM">
...
  <SLM:component name="screen-ready">
    <SLM:command launch="builtin">no_op</SLM:command>
    <SLM:waitfor wait="pathname">/dev/screen</SLM:waitfor>
  </SLM:component>
...
  <SLM:component name="resarb">
    <SLM:command>/base/bin/resarb</SLM:command>
    <SLM:stop stop="signal">SIGTERM</SLM:stop>
  </SLM:component>
...
  <SLM:component name="sensor">
    <SLM:command>/base/bin/sensor</SLM:command>
    <SLM:args>-U 521:521,1001 -r /accounts/1000/shared/camera -c /base/etc/system/config/adas_example_capture.conf</SLM:args>
    <SLM:depend>resarb</SLM:depend>
    <SLM:depend>screen-ready</SLM:depend>
  </SLM:component>
...
  <SLM:component name="adas_example">
    <SLM:command>/base/usr/bin/adas_example</SLM:command>
    <SLM:args>-pointcloud</SLM:args>
    <SLM:depend>sensor</SLM:depend>
    <SLM:stop stop="signal">SIGTERM</SLM:stop>
  </SLM:component>
...
</SLM:system>

If your application uses other sensors, in addition to a file camera, more components and dependencies than what's shown here may be required in the SLM configuration file.

Example: SLM configuration for USB cameras to boot immediately

Updated: April 19, 2023

This example describes how to set up a SLM file to use a USB camera immediately after the target boots.

For this configuration, you must ensure that you have a USB camera configured in the sensor configuration file. For example: 

begin SENSOR_UNIT_1
    type = usb_camera
    usb_driver_path = /dev/usb/io-usb-otg
    name = front-camera
    position = 0, 0, 0
    direction = 0, 0, 1
    address = -1, -1, -1, -1
end SENSOR_UNIT_1

For more information, see the “Example: Sensor configuration file for USB camera” section.

To configure your SLM configuration file to start using a USB camera, here's what you need to do:
  • If it's not already part of your IFS image, start the USB driver before you start the Sensor service (sensor).

    For a USB camera to start immediately after the board boots, the USB driver must start before the Sensor service. If the USB driver isn't already part of your IFS image, you need to start the USB driver in your SLM configuration and have the Sensor service depend on it. For example, you would specify that the sensor component depends on the usb component.

    If you aren't using a USB camera, you don't need to set up a dependency on the usb component in your SLM configuration file.

  • Ensure that the Sensor service has a dependency on Screen.

    For example, start the sensor component with a dependency to wait until the screen_ready component comes up.

  • Start your camera application.

Your SLM configuration should include components as follows: 

<SLM:system xmlns:SLM="SLM">
...
  <SLM:component name="screen-ready">
    <SLM:command launch="builtin">no_op</SLM:command>
    <SLM:waitfor wait="pathname">/dev/screen</SLM:waitfor>
  </SLM:component>
...
  <!-- Include a usb component to start the USB driver using SLM
   if the USB driver isn't already part of your IFS image.
  -->
    <SLM:component name="usb">
    <SLM:command>io-usb-otg</SLM:command>
    <SLM:args>-n /dev/usb/io-usb-otg -d hcd-xhci</SLM:args>
  </SLM:component>
...
  <SLM:component name="resarb">
    <SLM:command>/base/bin/resarb</SLM:command>
    <SLM:stop stop="signal">SIGTERM</SLM:stop>
  </SLM:component>
...
  <SLM:component name="sensor">
    <SLM:command>/base/bin/sensor</SLM:command>
    <SLM:args>-U 521:521,1001 -r /accounts/1000/shared/camera -c /base/etc/system/config/usb_camera.conf</SLM:args>
    <!-- Add a dependency on the usb component if you are starting the USB driver through SLM. -->
    <SLM:depend>usb</SLM:depend>
    <SLM:depend>screen-ready</SLM:depend>
  </SLM:component>
...
  <SLM:component name="adas_example">
    <SLM:command>/base/usr/bin/adas_example</SLM:command>
    <SLM:args>-pointcloud</SLM:args>
    <SLM:depend>sensor</SLM:depend>
    <SLM:stop stop="signal">SIGTERM</SLM:stop>
  </SLM:component>
...
</SLM:system>

If your application uses other sensors, in addition to a USB camera, more components and dependencies than what's shown here may be required in the SLM configuration file.