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References: <20220516100401.7639-1-ojeda@kernel.org>
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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 18 May 2022 08:52:37 +0100
Message-ID: <CAK8P3a3Z5qBQWUbPNEHhPDNX0XC8CQk+dUtC9K_=N3AXK2uHHA@mail.gmail.com>
Subject: Re: [PATCH v1] binder: convert `BINDER_*` ioctl `#define`s into an `enum`
To:     Miguel Ojeda <ojeda@kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Li Li <dualli@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Wedson Almeida Filho <wedsonaf@google.com>
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On Mon, May 16, 2022 at 11:04 AM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> -#define BINDER_WRITE_READ              _IOWR('b', 1, struct binder_write_read)
> -#define BINDER_SET_IDLE_TIMEOUT                _IOW('b', 3, __s64)
> -#define BINDER_SET_MAX_THREADS         _IOW('b', 5, __u32)
> -#define BINDER_SET_IDLE_PRIORITY       _IOW('b', 6, __s32)
> -#define BINDER_SET_CONTEXT_MGR         _IOW('b', 7, __s32)
> -#define BINDER_THREAD_EXIT             _IOW('b', 8, __s32)
> -#define BINDER_VERSION                 _IOWR('b', 9, struct binder_version)
> -#define BINDER_GET_NODE_DEBUG_INFO     _IOWR('b', 11, struct binder_node_debug_info)
> -#define BINDER_GET_NODE_INFO_FOR_REF   _IOWR('b', 12, struct binder_node_info_for_ref)
> -#define BINDER_SET_CONTEXT_MGR_EXT     _IOW('b', 13, struct flat_binder_object)
> -#define BINDER_FREEZE                  _IOW('b', 14, struct binder_freeze_info)
> -#define BINDER_GET_FROZEN_INFO         _IOWR('b', 15, struct binder_frozen_status_info)
> -#define BINDER_ENABLE_ONEWAY_SPAM_DETECTION    _IOW('b', 16, __u32)
> +enum {
> +       BINDER_WRITE_READ                       = _IOWR('b', 1, struct binder_write_read),
> +       BINDER_SET_IDLE_TIMEOUT                 = _IOW('b', 3, __s64),
> +       BINDER_SET_MAX_THREADS                  = _IOW('b', 5, __u32),
> +       BINDER_SET_IDLE_PRIORITY                = _IOW('b', 6, __s32),
> +       BINDER_SET_CONTEXT_MGR                  = _IOW('b', 7, __s32),
> +       BINDER_THREAD_EXIT                      = _IOW('b', 8, __s32),
> +       BINDER_VERSION                          = _IOWR('b', 9, struct binder_version),

I wonder if that breaks any tools that extract ioctl command number definitions
from kernel headers. I see one other header using enum, but everything else
has the #define. The main user of ioctl command definitions that comes to
mind is 'strace', but I don't know where they get the numbers from.

It's probably not a big deal as long as it's limited to binder, but it
may become
more of a problem if we do this for more subsystems over time.

         Arnd