From mboxrd@z Thu Jan  1 00:00:00 1970
From: Claude Code Review Bot <claude-review@example.com>
To: dri-devel-reviews@example.com
Subject: Claude review: drm: ensure blend mode supported if pixel format with alpha exposed
Date: Wed, 27 May 2026 14:23:00 +1000
Message-ID: <review-patch2-20260526181700.25310-3-leandro.ribeiro@collabora.com>
In-Reply-To: <20260526181700.25310-3-leandro.ribeiro@collabora.com>
References: <20260526181700.25310-1-leandro.ribeiro@collabora.com> <20260526181700.25310-3-leandro.ribeiro@collabora.com>
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Patch Review

**Potential NULL pointer dereference.** In `validate_blend_mode_for_alpha_f=
ormats()`:

```c
for (i =3D 0; i < plane->format_count; i++) {
    fmt =3D drm_format_info(plane->format_types[i]);
    if (fmt->has_alpha) {
```

`drm_format_info()` can return NULL for unknown formats (it only does a `WA=
RN_ON(!info)` internally, then returns NULL). If a buggy driver registers a=
n unknown fourcc, this validation function =E2=80=94 which exists precisely=
 to catch driver bugs =E2=80=94 would hit a NULL dereference on `fmt->has_a=
lpha`.

This should have a NULL check:

```c
fmt =3D drm_format_info(plane->format_types[i]);
if (fmt && fmt->has_alpha) {
```

In practice this is unlikely to trigger since any driver with an unknown fo=
rmat would already be very broken, but a validation function should be defe=
nsive.

**Otherwise the logic is correct.** The early return when `blend_mode_prope=
rty` is set avoids unnecessary iteration. The `break` after the first warni=
ng avoids spamming the log. The placement in `drm_mode_config_validate()` i=
n the existing `drm_for_each_plane` loop is efficient.

**Minor style nit:** The WARN format string is split across lines:

```c
WARN(1, "[PLANE:%d:%s] pixel format with alpha exposed but "
     "blend mode not setup", plane->base.id, plane->name);
```

"not setup" should be "not set up" (two words =E2=80=94 "setup" is a noun, =
"set up" is the verb/participle form). Very minor.

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