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References: <20240608-hid_bpf_struct_ops-v3-0-6ac6ade58329@kernel.org> <20240608-hid_bpf_struct_ops-v3-3-6ac6ade58329@kernel.org>
In-Reply-To: <20240608-hid_bpf_struct_ops-v3-3-6ac6ade58329@kernel.org>
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date: Mon, 10 Jun 2024 11:34:37 -0700
Message-ID: <CAADnVQJDZju=QMiAH=TpYHr6KQh3-TT-jNtJ-O2u7JstY5486Q@mail.gmail.com>
Subject: Re: [PATCH HID v3 03/16] HID: bpf: implement HID-BPF through bpf_struct_ops
To: Benjamin Tissoires <bentiss@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>, Jiri Kosina <jikos@kernel.org>, Jonathan Corbet <corbet@lwn.net>, 
	Alexei Starovoitov <ast@kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, 
	bpf <bpf@vger.kernel.org>, 
	"open list:HID CORE LAYER" <linux-input@vger.kernel.org>, 
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
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On Sat, Jun 8, 2024 at 2:01=E2=80=AFAM Benjamin Tissoires <bentiss@kernel.o=
rg> wrote:
>
> +
> +static int hid_bpf_ops_init_member(const struct btf_type *t,
> +                                const struct btf_member *member,
> +                                void *kdata, const void *udata)
> +{
> +       u32 moff =3D __btf_member_bit_offset(t, member) / 8;
> +       u32 flags;
> +
> +       switch (moff) {
> +       case offsetof(struct hid_bpf_ops, hid_id):
> +               /* For hid_id and flags fields, this function has to copy=
 it
> +                * and return 1 to indicate that the data has been handle=
d by
> +                * the struct_ops type, or the verifier will reject the m=
ap if
> +                * the value of those fields is not zero.
> +                */
> +               ((struct hid_bpf_ops *)kdata)->hid_id =3D ((struct hid_bp=
f_ops *)udata)->hid_id;
> +               return 1;
> +       case offsetof(struct hid_bpf_ops, flags):
> +               flags =3D ((struct hid_bpf_ops *)udata)->flags;
> +               if (flags & ~BPF_F_BEFORE)
> +                       return -EINVAL;
> +               ((struct hid_bpf_ops *)kdata)->flags =3D flags;

minor nit: I'd cast kdata/udate in the beginning of
the function to make the lines shorter and less verbose.
Similar to how bpf_tcp_ca_init_member() does it.

Acked-by: Alexei Starovoitov <ast@kernel.org>