Claude review: drm/rockchip: dw_hdmi: Propagate bus format to display driver

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

Patch Review

**Status: Bug found**

This patch reads the negotiated bus format from the bridge state and maps it to the rockchip output mode (AAAA or YUV420).

**Bug**: In `dw_hdmi_rockchip_get_bus_format()`:

```c
bridge_state = drm_atomic_get_bridge_state(conn_state->state, bridge);
if (!bridge_state)
	return 0;
```

`drm_atomic_get_bridge_state()` returns `ERR_CAST()` on failure (i.e., `ERR_PTR`), **not** NULL. This NULL check will never catch an error. The code will proceed with an `ERR_PTR` value in `bridge_state` and dereference it, causing a crash.

This should be:
```c
if (IS_ERR(bridge_state))
	return 0;
```

Or better, since this is called from `atomic_check`, the error should be propagated:
```c
if (IS_ERR(bridge_state))
	return PTR_ERR(bridge_state);
```

But that would require changing the return type of `dw_hdmi_rockchip_get_bus_format()` to handle errors. The simplest safe fix is to use `IS_ERR(bridge_state)`.

**Minor**: The commit message has a typo: "inpact" should be "impact".

**Additional note**: The `__free(drm_bridge_put)` cleanup annotation on `bridge` is a nice use of scope-based resource management for the bridge reference obtained from `drm_bridge_chain_get_first_bridge()`.

The `MEDIA_BUS_FMT_FIXED` fallthrough to `MEDIA_BUS_FMT_RGB888_1X24` is the right default behavior. The switch covers RGB, YCbCr 4:4:4, and YCbCr 4:2:0 at both 8 and 10 bit depths.

The `s->bus_format = bus_format` assignment correctly propagates the format to `rockchip_crtc_state`, which has the `bus_format` field (verified in `rockchip_drm_drv.h`).

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Generated by Claude Code Patch Reviewer