Claude review: drm/mipi-dbi: Provide callbacks for atomic interfaces

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

Patch Review

Provides new standalone atomic helper functions (`drm_mipi_dbi_*` prefix) and initializer macros (`DRM_MIPI_DBI_PLANE_FUNCS`, `DRM_MIPI_DBI_CRTC_FUNCS`, etc.) for drivers to use with regular atomic modesetting.

**Bug — uninitialized variable:** In `drm_mipi_dbi_plane_helper_atomic_check()` (mbox line ~1106):
```c
struct drm_crtc_state *new_crtc_state;

if (new_plane_state->crtc)
    new_crtc_state = drm_atomic_get_new_crtc_state(state, new_plane_state->crtc);

ret = drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state, ...);
```
When `new_plane_state->crtc` is NULL (plane being disabled), `new_crtc_state` is **used uninitialized**. While `drm_atomic_helper_check_plane_state()` does handle `crtc_state == NULL`, it will receive stack garbage rather than NULL. This must be:
```c
struct drm_crtc_state *new_crtc_state = NULL;
```

**Minor:** The tail of the same function is redundant:
```c
if (ret)
    return ret;
else if (!new_plane_state->visible)
    return 0;
return 0;
```
This could simply be `return ret;`. The `else if` branch suggests future checks were intended but not yet added.

**Minor:** Moving `drm_gem_atomic_helper.h`, `drm_gem_framebuffer_helper.h`, `drm_probe_helper.h`, and `drm_atomic_state_helper.h` into `drm_mipi_dbi.h` (to support the initializer macros) adds transitive header weight to all includers. This is a common trade-off for macro-based initializers.

### PATCH 4 (04/16): drm/hx8357d: Use regular atomic helpers

Standard mechanical conversion. Introduces `struct hx8357d_device` wrapping `mipi_dbi_dev` with embedded plane/crtc/encoder/connector. Converts `yx240qv29_enable` to `hx8357d_crtc_helper_atomic_enable`. Probe open-codes the pipeline setup using the new `DRM_MIPI_DBI_*` macros.

No issues found.

### PATCH 5 (05/16): drm/ili9163: Use regular atomic helpers

Identical structural conversion as hx8357d.

No issues found.

### PATCH 6 (06/16): drm/ili9225: Use regular atomic helpers

More complex conversion since ili9225 has custom update and disable callbacks. Uses `DRM_GEM_SHADOW_PLANE_HELPER_FUNCS` instead of `DRM_MIPI_DBI_PLANE_HELPER_FUNCS` since it provides its own `atomic_update`. The old `!pipe->crtc.state->active` guard is correctly replaced with `!plane_state->fb` (standard pattern for regular atomic helpers where the framework manages CRTC-active gating).

No issues found.

### PATCH 7 (07/16): drm/ili9341: Use regular atomic helpers

Standard mechanical conversion, same pattern as hx8357d/ili9163.

No issues found.

### PATCH 8 (08/16): drm/ili9486: Use regular atomic helpers

Standard mechanical conversion. Minor improvement: renames old `waveshare_enable` to `ili9486_crtc_helper_atomic_enable` for consistency.

No issues found.

### PATCH 9 (09/16): drm/mi0283qt: Use regular atomic helpers

Standard mechanical conversion.

No issues found.

### PATCH 10 (10/16): drm/panel-mipi-dbi: Use regular atomic helpers

Slightly different from others because the pixel format is determined dynamically at probe time. Correctly passes the runtime `formats[]` array to `drm_universal_plane_init()` while using `formats[0]` (native format) for `drm_mipi_dbi_dev_init()` buffer sizing.

No issues found.

### PATCH 11 (11/16): drm/st7586: Use regular atomic helpers

Complex conversion like ili9225 — custom update, enable, and disable. Uses `DRM_FORMAT_XRGB8888` only (this driver does internal 2bpp grayscale conversion). Sets `preferred_depth = 24` to match XRGB8888.

**Minor style inconsistency:** `st7586_plane_helper_atomic_update` uses `if (drm_dev_enter(...)) { ... }` while ili9225's equivalent uses the early-return pattern. Both are correct but inconsistent.

### PATCH 12 (12/16): drm/st7735r: Rename struct st7735r_priv to struct st7735r_device

Purely cosmetic rename to follow DRM naming conventions. Adds `to_st7735r_device()` upcast helper.

No issues found.

### PATCH 13 (13/16): drm/st7735r: Rename priv variable to st7735r

Purely cosmetic rename of local variable `priv` → `st7735r`.

No issues found.

### PATCH 14 (14/16): drm/st7735r: Use regular atomic helpers

Standard mechanical conversion for st7735r. Uses the `DRM_MIPI_DBI_*` macros. Only custom callback is `st7735r_crtc_helper_atomic_enable`.

No issues found.

### PATCH 15 (15/16): drm/mipi-dbi: Remove simple-display helpers from mipi-dbi

Large deletion patch removing all now-unused simple-display-pipe wrapper functions (`mipi_dbi_pipe_update`, `mipi_dbi_pipe_disable`, `mipi_dbi_enable_flush`, `mipi_dbi_dev_init_with_formats`, `mipi_dbi_dev_init`, etc.), the `DRM_MIPI_DBI_SIMPLE_DISPLAY_PIPE_FUNCS` macro, and the `pipe`/`connector` fields from `struct mipi_dbi_dev`.

No issues found. Clean removal of dead code.

### PATCH 16 (16/16): drm/simple-kms: Deprecate simple-kms helpers

Strips all kerneldoc from `drm_simple_kms_helper.c`/`.h`, removes the "Simple KMS Helper Reference" from the GPU documentation, and adds TODO items for converting remaining users.

**Three typos:**
- Commit message (line 5016): `"voluteers"` → `"volunteers"`
- TODO item (line 5105): `"fucntions"` → `"functions"`
- Header deprecation comment (lines 5306-5307):
  ```
  Simple KMS helpers are deprected in favor of regular atomic helpers. Do not
  use the min new code.
  ```
  Should be: `"deprecated"` and `"Do not use them in new code."`

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