netdev - Re: linux-next: build failure after merge of the bpf-next tree

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Date: Tue, 25 Jun 2024 17:54:47 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Thinker Li <thinker.li@...il.com>
Cc: Mark Brown <broonie@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov <ast@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>, 
	Jiri Kosina <jikos@...nel.org>, Martin KaFai Lau <martin.lau@...nel.org>, 
	linux-input@...r.kernel.org, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 
	Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the bpf-next tree

On Jun 24 2024, Thinker Li wrote:
> Hi Mark,
> 
> I'm sorry for not getting back to you sooner. I have been traveling
> since my last message.
> I guess this patch is for the HID tree. The changes in this patch are great.

Ok, thanks for the review. However, the need appears because there is a
conflicting update in the bpf tree.

May I ask the bpf maintainers (Daniel/Alexei/Andrii) for an immutable
tag I could merge to so I can take this patch from Mark?

> 
> However, I suggest you implement ".update" if you think it is
> reasonable for HID,
> although it is not a MUST-BE. ".update" provides a good feature that
> user space programs
> can update an implementation on the flight.

FWIW, Mark handles linux-next, so not sure he has deep knowledge of
HID-BPF, and not sure he wants too :)

Regarding .update, I'm not sure it's worth the effort for hid-bpf. Right
now HID-BPF programs are just a one-shot: you load them, pin them and
forget. This might be different when systemd starts implementing a HID
firewall, but we can cross that bridge when we see fit.

Cheers,
Benjamin

> 
> On Mon, Jun 17, 2024 at 11:16 AM Mark Brown <broonie@...nel.org> wrote:
> >
> > Hi all,
> >
> > After merging the bpf-next tree, today's linux-next build (x86_64
> > allmodconfig) failed like this:
> >
> > /tmp/next/build/drivers/hid/bpf/hid_bpf_struct_ops.c:280:16: error: initialization of 'int (*)(void *, struct bpf_link *)' from incompatible pointer type 'int (*)(void *)' [-Werror=incompatible-pointer-types]
> >   280 |         .reg = hid_bpf_reg,
> >       |                ^~~~~~~~~~~
> > /tmp/next/build/drivers/hid/bpf/hid_bpf_struct_ops.c:280:16: note: (near initialization for 'bpf_hid_bpf_ops.reg')
> > /tmp/next/build/drivers/hid/bpf/hid_bpf_struct_ops.c:281:18: error: initialization of 'void (*)(void *, struct bpf_link *)' from incompatible pointer type 'void (*)(void *)' [-Werror=incompatible-pointer-types]
> >   281 |         .unreg = hid_bpf_unreg,
> >       |                  ^~~~~~~~~~~~~
> > /tmp/next/build/drivers/hid/bpf/hid_bpf_struct_ops.c:281:18: note: (near initialization for 'bpf_hid_bpf_ops.unreg')
> >
> > Caused by commit
> >
> >   73287fe228721b ("bpf: pass bpf_struct_ops_link to callbacks in bpf_struct_ops.")
> >
> > interacting with commit
> >
> >   ebc0d8093e8c97 ("HID: bpf: implement HID-BPF through bpf_struct_ops")
> >
> > from the HID tree.
> >
> > I've fixed it up as below:
> >
> > From e8aeaba00440845f9bd8d6183ca5d7383a678cd3 Mon Sep 17 00:00:00 2001
> > From: Mark Brown <broonie@...nel.org>
> > Date: Mon, 17 Jun 2024 19:02:27 +0100
> > Subject: [PATCH] HID: bpf: Fix up build
> >
> > Fix up build error due to 73287fe228721b ("bpf: pass bpf_struct_ops_link to callbacks in bpf_struct_ops.")
> >
> > Signed-off-by: Mark Brown <broonie@...nel.org>
> > ---
> >  drivers/hid/bpf/hid_bpf_struct_ops.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c
> > index 5f200557ff12b..744318e7d936b 100644
> > --- a/drivers/hid/bpf/hid_bpf_struct_ops.c
> > +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c
> > @@ -175,7 +175,7 @@ static int hid_bpf_ops_init_member(const struct btf_type *t,
> >         return 0;
> >  }
> >
> > -static int hid_bpf_reg(void *kdata)
> > +static int hid_bpf_reg(void *kdata, struct bpf_link *link)
> >  {
> >         struct hid_bpf_ops *ops = kdata;
> >         struct hid_device *hdev;
> > @@ -229,7 +229,7 @@ static int hid_bpf_reg(void *kdata)
> >         return err;
> >  }
> >
> > -static void hid_bpf_unreg(void *kdata)
> > +static void hid_bpf_unreg(void *kdata, struct bpf_link *link)
> >  {
> >         struct hid_bpf_ops *ops = kdata;
> >         struct hid_device *hdev;
> > --
> > 2.39.2
> >