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From:   Benjamin Tissoires <benjamin.tissoires@redhat.com>
To:     Greg KH <gregkh@linuxfoundation.org>,
        Jiri Kosina <jikos@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>, Shuah Khan <shuah@kernel.org>,
        Dave Marchevsky <davemarchevsky@fb.com>,
        Joe Stringer <joe@cilium.io>, Jonathan Corbet <corbet@lwn.net>
Cc:     Tero Kristo <tero.kristo@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-input@vger.kernel.org,
        netdev@vger.kernel.org, bpf@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>
Subject: [PATCH bpf-next v5 05/17] HID: core: store the unique system identifier in hid_device
Date:   Wed, 18 May 2022 22:59:12 +0200
Message-Id: <20220518205924.399291-6-benjamin.tissoires@redhat.com>
In-Reply-To: <20220518205924.399291-1-benjamin.tissoires@redhat.com>
References: <20220518205924.399291-1-benjamin.tissoires@redhat.com>
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This unique identifier is currently used only for ensuring uniqueness in
sysfs. However, this could be handful for userspace to refer to a specific
hid_device by this id.

2 use cases are in my mind: LEDs (and their naming convention), and
HID-BPF.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

---

new in v5
---
 drivers/hid/hid-core.c | 4 +++-
 include/linux/hid.h    | 2 ++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index db925794fbe6..e78f35cfd2d1 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2735,10 +2735,12 @@ int hid_add_device(struct hid_device *hdev)
 			hid_warn(hdev, "bad device descriptor (%d)\n", ret);
 	}
 
+	hdev->id = atomic_inc_return(&id);
+
 	/* XXX hack, any other cleaner solution after the driver core
 	 * is converted to allow more than 20 bytes as the device name? */
 	dev_set_name(&hdev->dev, "%04X:%04X:%04X.%04X", hdev->bus,
-		     hdev->vendor, hdev->product, atomic_inc_return(&id));
+		     hdev->vendor, hdev->product, hdev->id);
 
 	hid_debug_register(hdev, dev_name(&hdev->dev));
 	ret = device_add(&hdev->dev);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 4363a63b9775..a43dd17bc78f 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -658,6 +658,8 @@ struct hid_device {							/* device report descriptor */
 	struct list_head debug_list;
 	spinlock_t  debug_list_lock;
 	wait_queue_head_t debug_wait;
+
+	unsigned int id;						/* system unique id */
 };
 
 #define to_hid_device(pdev) \
-- 
2.36.1