driver: __init と __exit を指定

[masnagam]

モジュールの初期化および終了関数にそれぞれ __init と __exit を指定した．これらマクロを使用していなくても大きな問題は発生しないと考えられるが，一般的な作法として追加した．

これらマクロの説明は以下を参照:

• https://tldp.org/LDP/lkmpg/2.4/html/x281.htm
• https://fastbitlab.com/linux-device-driver-programming-lecture-18-__init-and-__exit-macros/
• https://shnoh171.github.io/linux%20kernel/2019/09/01/linux-kernel-module-basics.html

ビルド確認

archlinxイメージを使用

$ docker run --rm -it -v $(pwd):/px4_drv archlinux
[root@1245c254444d px4_drv]# uname -a
Linux 1245c254444d 6.15.7-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 17 Jul 2025 21:05:29 +0000 x86_64 GNU/Linux

以下を実行

pacman -Sy --noconfirm dkms gcc linux-headers make
cp -a ./ /usr/src/px4_drv-0.5.4
dkms add px4_drv/0.5.4
dkms install px4_drv/0.5.4
find /lib/modules -name px4_drv.ko

TODO

ビルド時に以下のメッセージが表示される．

Deprecated feature: CLEAN (/var/lib/dkms/px4_drv/0.5.4/source/dkms.conf)

以下の修正でCLEANはdkmsから削除された:

• dkms-project/dkms@754f26f

Summary by CodeRabbit

• リファクタ
  • 新しいカーネルバージョン（6.15.4以降）に対応するため、初期化およびクリーンアップ処理の内部実装を調整しました。動作や機能には変更ありません。

[coderabbitai]

Walkthrough

driver/driver_module.c の初期化関数とクリーンアップ関数に、カーネルバージョン 6.15.4 以上の場合のみ __init および __exit マクロを付与するよう変更されました。関数名や制御フロー自体は変更されていません。

Changes

ファイル	変更概要
driver/driver_module.c	カーネル6.15.4以上で初期化関数に__init、クリーンアップ関数に__exitマクロを付与。関数名やロジックは変更なし。

Poem

うさぎがコードにぴょんと跳ね、
マクロを添えて新たな種、
カーネル見守り静かに待つ、
初期化も終了も、
うさぎのしっぽでふわり包む。
🐇✨

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Reviewing files that changed from the base of the PR and between 5ac1fca and fe259b5.

📒 Files selected for processing (1)

• driver/driver_module.c (2 hunks)

🔇 Additional comments (1)

driver/driver_module.c (1)

19-24: バージョン分岐が過剰です ― module_init / module_exit と __init / __exit は古いカーネルでも利用可能

__init / __exit も module_init / module_exit も 2.6 系から既に存在しており、6.15 以降に限定する理由はありません。
現状の分岐では

• 6.15 未満のカーネルで “グローバル記号 init_module / cleanup_module” を公開する旧式 API を使う
• 6.15 以上で “静的関数 + module_init/module_exit” を使う

という二重実装になり、保守コストが上がります。どのバージョンでも後者（静的関数 + マクロ）のみで問題なく動作します。

提案 diff（分岐を削除し、シンプルに統一）:

-#if LINUX_VERSION_CODE >= KERNEL_VERSION(6,15,4)
-static int __init m_init(void)
-#else
-int init_module(void)
-#endif
+static int __init m_init(void)

 ...

-#if LINUX_VERSION_CODE >= KERNEL_VERSION(6,15,4)
-static void __exit m_cleanup(void)
-#else
-void cleanup_module(void)
-#endif
+static void __exit m_cleanup(void)

 ...

-#if LINUX_VERSION_CODE >= KERNEL_VERSION(6,15,4)
 module_init(m_init);
 module_exit(m_cleanup);
-#endif

これで全カーネルで同一コードパスとなり、不要な条件分岐・重複が排除できます。
互換性に懸念があれば alias マクロで旧シンボルを残す手も取れますが、通常は不要です。
[ suggest_essential_refactor ]

Also applies to: 55-67

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[tsukumijima]

ありがとうございます！