syslog/ramlog: remove magic flag

[anchao]

Summary

syslog/ramlog: remove magic flag

1. remove magic flag
2. move g_sysdev to bss
3. clear ramlog buffer only if in custom section

Signed-off-by: chao an [email protected]

Impact

N/A

Testing

ci-check

[nuttxpr]

[Experimental Bot, please feedback here]

This PR appears to mostly meet the NuttX requirements, but is missing some information:

What's good:

• Summary: Provides a high-level overview of the changes being made. However, it could be more descriptive. What is the magic flag and why should it be removed?
• Testing: Indicates that CI checks were performed, which is good. However, providing actual log snippets (even if shortened) would be even better.

What needs improvement:

• Impact: While marking everything as N/A might be technically correct, it's unlikely that every category is truly unaffected. For example:
  • Impact on build: Even small code changes can alter build times or memory usage. Consider if this is relevant.
  • Impact on compatibility: Does removing this magic flag potentially break any existing configurations or use cases?
• Testing:
  • Be specific about the build host and target(s) used for testing.
  • Provide snippets of the testing logs before and after the change. This helps reviewers quickly understand the impact of the changes.

Recommendation:

Before merging, expand on the Impact section, even if briefly, to confirm that the potential implications have been considered. Additionally, enhance the Testing section with specifics about the test environment and relevant log snippets.

[acassis]

@anchao I think the magic flag is useful to search where the ramlog starts in the memory in case where someone is debug NuttX bringup and doesn't have serial console working.

Maybe @patacongo can confirm the reason he included it.

[patacongo]

The flag was used to distinguish between a cold start and a reset. This was added by Xiaomi just a few months ago. See

commit 0da8755fbce536da81894694c47905430d38848b
Author: yuanyongjian <[email protected]>
Date:   Thu Nov 23 13:02:47 2023 +0800

    syslog/ramlog:Add tags to distinguish between hot start and cold start

    Signed-off-by: yuanyongjian <[email protected]>

[anchao]

@acassis @patacongo This PR will use the header pointer to check if it is hot/cold reset, so removing the magic will give the same functionality.

[xiaoxiang781216]

@acassis @patacongo This PR will use the header pointer to check if it is hot/cold reset, so removing the magic will give the same functionality.

but the check doesn't work since g_sysdev is initialized to zero by boot every time.

[xiaoxiang781216]

what's the benefit to change the static data initialization to the runtime initialization?