Claude review: drm/ras: Introduce error threshold

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

Patch Review

This patch adds the core DRM RAS infrastructure for threshold queries. It follows the existing error counter pattern closely.

**Looks good:**
- The netlink policy tables, ops registrations, and `GENL_ADMIN_PERM` flags are all correct.
- Error handling with `genlmsg_cancel`/`nlmsg_free` on failure is done properly (addressed from v2 review).
- Documentation is clear and includes examples.

**Issues:**

1. **Missing locking around `xa_load` in threshold functions**: `get_node_error_threshold()` and `set_node_error_threshold()` call `xa_load()` on the shared xarray without any locking, same as the existing counter code. While this is consistent with the existing pattern, `set_error_threshold` is a write path — if concurrent set/get is expected, consider whether the driver callbacks need to be thread-safe (the docs should mention this responsibility). This is an existing issue inherited from the counter path, but worth documenting for the new threshold callbacks since set introduces a mutation operation that didn't exist with query-only.

2. **`query_error_threshold` callback signature asymmetry**: The `query_error_threshold` callback returns the `name` output parameter, but `set_error_threshold` does not take a name. This means `get_node_error_threshold` validates the error ID range AND asks the driver for the name, while `set_node_error_threshold` validates the range and just calls the driver. This is fine architecturally, but the name output from `query_error_threshold` exists only to populate the netlink reply — it would be cleaner to separate the "get name" concern from the "get threshold" concern, or document why they're coupled.

3. **`set-error-threshold` YAML spec has no reply section**:
```yaml
    -
      name: set-error-threshold
      doc: >-
           Set error threshold of a given counter.
      attribute-set: error-counter-attrs
      flags: [admin-perm]
      do:
        request:
          attributes:
            - node-id
            - error-id
            - error-threshold
```
There's no `reply:` block. This is fine if the intent is to return nothing on success (like `clear-error-counter`), but worth confirming that the generated code matches expectations.

4. **`get-error-threshold` spec missing `node-id` in reply**: The reply attributes are `error-id`, `error-name`, `error-threshold` — which matches `msg_reply_threshold()`. But it's inconsistent with `get-error-counter` which also doesn't include `node-id` in the reply, so this is consistent with the existing pattern.

---
Generated by Claude Code Patch Reviewer