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 [off-list ref] wrote:

quoted

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@kernel.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@kernel.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