Claude review: dyndbg: factor ddebug_match_desc out from ddebug_change

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Commit message quality:** Good. Clearly explains the motivation — extracting the inner-loop filter logic into a separate function for readability.

**Review of the changes:**

This is a straightforward, clean code refactor. The new function:

```c
static bool ddebug_match_desc(const struct ddebug_query *query,
			      struct _ddebug *dp,
			      int valid_class)
```

extracts exactly the per-descriptor matching logic from `ddebug_change()`, converting each `continue` to `return false`. The transformation is correct — each filter condition is preserved identically.

**Minor observations:**

1. The `dp` parameter could be `const`:
```c
			      struct _ddebug *dp,
```
Since `ddebug_match_desc` only reads from `dp`, marking it `const struct _ddebug *dp` would better express intent. This is a nit, not a blocker.

2. The commit message says "also fix checkpatch complaints about spaces and braces." Looking at the diff, the only style change I can see is the spacing around `query->format+1` → `query->format + 1` (line 702 vs the removed line 750). The commit message should either enumerate what style fixes were made or just omit this note if it's a single trivial whitespace change. Mixing style fixes with refactoring in one commit is generally acceptable when the style fix is trivial like this one.

3. The function placement is good — it's placed immediately above `ddebug_change()` where it's called, with the existing block comment acting as a natural separator.

**Verdict:** Clean, correct refactoring. No functional changes. Reviewed-by worthy.

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