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From: Benjamin Tissoires <bentiss@kernel.org>
Date: Fri, 07 Jun 2024 17:28:36 +0200
Subject: [PATCH HID v2 16/16] HID: bpf: make part of struct hid_device
 writable
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Message-Id: <20240607-hid_bpf_struct_ops-v2-16-3f95f4d02292@kernel.org>
References: <20240607-hid_bpf_struct_ops-v2-0-3f95f4d02292@kernel.org>
In-Reply-To: <20240607-hid_bpf_struct_ops-v2-0-3f95f4d02292@kernel.org>
To: Shuah Khan <shuah@kernel.org>, Jiri Kosina <jikos@kernel.org>, 
 Jonathan Corbet <corbet@lwn.net>, Alexei Starovoitov <ast@kernel.org>
Cc: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, 
 bpf@vger.kernel.org, linux-input@vger.kernel.org, linux-doc@vger.kernel.org, 
 Benjamin Tissoires <bentiss@kernel.org>

It is useful to change the name, the phys and/or the uniq of a
struct hid_device during .rdesc_fixup().

For example, hid-uclogic.ko changes the uniq to store the firmware version
to differentiate between 2 devices sharing the same PID. In the same
way, changing the device name is useful when the device export 3 nodes,
all with the same name.

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

---

new in v2
---
 drivers/hid/bpf/hid_bpf_struct_ops.c | 3 +++
 include/linux/hid_bpf.h              | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c
index 944e6d91a36b..14a4c64ae242 100644
--- a/drivers/hid/bpf/hid_bpf_struct_ops.c
+++ b/drivers/hid/bpf/hid_bpf_struct_ops.c
@@ -74,6 +74,9 @@ static int hid_bpf_ops_btf_struct_access(struct bpf_verifier_log *log,
 
 	const struct hid_bpf_offset_write_range write_ranges[] = {
 		WRITE_RANGE(hid_bpf_ctx, retval, 0, 0),
+		WRITE_RANGE(hid_device, name, 0, -1), /* minus 1 to ensure \0 at the end */
+		WRITE_RANGE(hid_device, uniq, 0, -1), /* minus 1 to ensure \0 at the end */
+		WRITE_RANGE(hid_device, phys, 0, -1), /* minus 1 to ensure \0 at the end */
 	};
 #undef WRITE_RANGE
 	const struct btf_type *state = NULL;
diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h
index 88ab4925bdaa..ff30cbc0a090 100644
--- a/include/linux/hid_bpf.h
+++ b/include/linux/hid_bpf.h
@@ -43,7 +43,7 @@ struct hid_device;
  * ``hid`` and ``allocated_size`` are read-only, ``size`` and ``retval`` are read-write.
  */
 struct hid_bpf_ctx {
-	const struct hid_device *hid;
+	struct hid_device *hid;
 	__u32 allocated_size;
 	union {
 		__s32 retval;

-- 
2.44.0