Claude review: accel/amdxdna: Return errors for failed debug BO commands

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

Patch Review

**Hunk 1 — `aie2_sched_drvcmd_resp_handler` refactor (lines 305–321)**

Good cleanup. The original code had a subtle bug: when `data` was NULL, it jumped to `out` with `ret = 0` and never wrote `job->drv_cmd->result`, leaving it at whatever the caller initialized (zero via `{ 0 }`). Callers check `if (cmd.result)` to detect failure, so they'd see success.

The new code:
```c
if (unlikely(!data || size != sizeof(u32))) {
    job->drv_cmd->result = U32_MAX;
    ret = -EINVAL;
} else {
    job->drv_cmd->result = readl(data);
}
```

This correctly handles both error paths: `ret = -EINVAL` for the return value, and `U32_MAX` as the result sentinel so callers checking `cmd.result` also see a failure. The `if/else` replacing the `goto out` pattern is cleaner for this two-case logic.

**Hunk 2 — `aie2_hwctx_cfg_debug_bo` missing error return (line 940)**

This is the core bug. Before the fix:
```c
aie2_cmd_wait(hwctx, seq);
if (cmd.result) {
    XDNA_ERR(xdna, "Response failure 0x%x", cmd.result);
    goto put_obj;
}
```

At this point `ret` is still 0 from the successful `amdxdna_cmd_submit` call, so jumping to `put_obj` returns success to userspace despite logging the error. The fix adding `ret = -EINVAL` is correct and matches the pattern already used in `aie2_hwctx_sync_debug_bo` (line 994 in the tree).

**Minor observation on commit message:** The commit message says "The config and sync debug BO commands currently may report success even when the operation fails." However, `aie2_hwctx_sync_debug_bo` already correctly returns `-EINVAL` when `cmd.result` is non-zero (tree lines 992–994). The "sync" part of the fix is only via the response handler change (the `data == NULL` path), not a missing error return like the config function had. This is technically accurate but could be clearer — the config function had two bugs (response handler + missing ret assignment) while the sync function only had the response handler one.

**No other issues found.** The patch is correct and ready to merge.

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