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Display Debugging with display_debug

The display_debug command in the ChromeOS Shell provides a suite of tools for diagnosing and troubleshooting display-related issues on ChromeOS devices. These tools allow users to collect logs, adjust tracing verbosity, and follow structured debugging steps.

Subcommands and Usage

1. trace_start

Enable detailed tracing for display debugging.

bash display_debug trace_start

This increases the size and verbosity of logging through drm_trace.

2. trace_stop

Disable detailed tracing and reset logging settings to default.

bash display_debug trace_stop

This command is useful for stopping verbose logging once debugging is complete.

3. trace_annotate

Append custom messages to the drm_trace log for additional context.

bash display_debug trace_annotate <message>

Replace <message> with a string to describe a specific event or observation.

4. diagnose

Retrieve step-by-step instructions for debugging display issues.

bash display_debug diagnose

This outputs a sequence of actions that can help identify and resolve common display problems.

Example Usage

Enabling Tracing for Debugging

```bash

Start detailed tracing

display_debug trace_start

Add a custom message to the log

display_debug trace_annotate "Started tracing after screen flickering issue observed" ```

Stopping Tracing

```bash

Stop tracing and reset to default logging

display_debug trace_stop ```

Getting Debugging Instructions

```bash

Retrieve diagnostic steps

display_debug diagnose ```

Best Practices

  1. Enable Tracing When Issues Occur
  2. Use trace_start to capture detailed logs during display issues.

  3. Annotate logs with key events using trace_annotate.

  4. Follow Diagnostic Steps

  5. Use the diagnose command to get clear troubleshooting guidance.

  6. Review logs for errors or anomalies after collecting data.

  7. Stop Tracing After Debugging

  8. Always use trace_stop to reset logging settings after debugging to minimize unnecessary log usage.

This tool is essential for developers and advanced users aiming to pinpoint and resolve display-related problems efficiently.