How to Fix: Linux setterm -powersave - error: "cannont (un)set powersave mode"
Linux setterm -powersave error: unable to power down backlight.
📋 Table of Contents
The error 'cannot (un)set powersave mode: Invalid argument' when using the `setterm -powersave` command on Linux systems can be frustrating for users trying to control the backlight of an LCD panel. This issue affects users who are trying to power down the backlight completely, but instead receive an error message indicating that the `-powersave` option is invalid.
This problem occurs when the system's display settings are not properly configured or when there is a conflict with other display-related software. In this guide, we will explore the root causes of this issue and provide two alternative methods to control the backlight power on your Linux system.
🛑 Root Causes of the Error
- The primary reason for this error is that the `-powersave` option in `setterm` is not a valid argument for controlling the display's powersave mode. The `powersave` command is used to adjust the screen's brightness and power consumption, but it does not provide a way to completely power down the backlight. This is because the backlight control is typically handled by the device's hardware or a separate driver.
- An alternative reason for this issue could be that there is a conflict with other display-related software, such as X11 or a custom display manager, which may be interfering with the `setterm` command. In some cases, these conflicts can cause the `-powersave` option to appear as an invalid argument.
✅ Best Solutions to Fix It
Using sysfs to control backlight power
- Step 1: To use sysfs to control the backlight power, you need to identify the device file that controls the backlight. This can usually be found in the `/sys/class/backlight/` directory. For example, on an O2 Joggler device, the backlight device file is `/sys/class/backlight/lcd_backlight/brightness`.
- Step 2: Once you have identified the device file, you can use the `echo` command to set the backlight power level to 0. For example: `echo 0 > /sys/class/backlight/lcd_backlight/brightness`. This will completely power down the backlight.
- Step 3: Note that setting the backlight power level to 0 may not work if there is a conflict with other display-related software or if the device's hardware does not support this feature.
Using a custom driver to control backlight power
- Step 1: If you have access to a custom driver that provides backlight control, you can use it to set the backlight power level to 0. For example, on an O2 Joggler device, you can use the `echo` command with the `sysfs` interface to set the backlight power level: `echo 0 > /sys/class/backlight/lcd_backlight/pseudo_file`.
- Step 2: Make sure that the custom driver is loaded and configured correctly before attempting to control the backlight. You may need to modify the device tree or add configuration files to enable this feature.
🎯 Final Words
In conclusion, the 'cannot (un)set powersave mode: Invalid argument' error when using `setterm -powersave` can be resolved by using sysfs to control the backlight power or a custom driver. By following the steps outlined in this guide, you should be able to completely power down the backlight on your Linux system.
❓ Frequently Asked Questions
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