linux-kernel - [PATCH RFC 3/4] HID: change return type of report

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Message-Id: <20240730-hid-const-fixup-v1-3-f667f9a653ba@weissschuh.net>
Date: Tue, 30 Jul 2024 23:35:59 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Jiri Kosina <jikos@...nel.org>, Benjamin Tissoires <bentiss@...nel.org>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH RFC 3/4] HID: change return type of report_fixup() to const

By allowing the drivers to return a "const *" they can constify their
static report arrays.
This makes it clear to driver authors that the HID core will not modify
those reports and they can be reused for multiple devices.
Furthermore security is slightly improved as those reports are protected
against accidental or malicious modifications.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 drivers/hid/hid-cmedia.c     | 2 +-
 drivers/hid/hid-sensor-hub.c | 2 +-
 include/linux/hid.h          | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/hid-cmedia.c b/drivers/hid/hid-cmedia.c
index 0681d8882ac8..d235dbedab8c 100644
--- a/drivers/hid/hid-cmedia.c
+++ b/drivers/hid/hid-cmedia.c
@@ -199,7 +199,7 @@ static struct hid_driver cmhid_driver = {
 	.input_mapping = cmhid_input_mapping,
 };
 
-static __u8 *cmhid_hs100b_report_fixup(struct hid_device *hid, __u8 *rdesc,
+static const __u8 *cmhid_hs100b_report_fixup(struct hid_device *hid, __u8 *rdesc,
 				       unsigned int *rsize)
 {
 	if (*rsize == HS100B_RDESC_ORIG_SIZE) {
diff --git a/drivers/hid/hid-sensor-hub.c b/drivers/hid/hid-sensor-hub.c
index 26e93a331a51..7bd86eef6ec7 100644
--- a/drivers/hid/hid-sensor-hub.c
+++ b/drivers/hid/hid-sensor-hub.c
@@ -580,7 +580,7 @@ void sensor_hub_device_close(struct hid_sensor_hub_device *hsdev)
 }
 EXPORT_SYMBOL_GPL(sensor_hub_device_close);
 
-static __u8 *sensor_hub_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+static const __u8 *sensor_hub_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 		unsigned int *rsize)
 {
 	/*
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 1533c9dcd3a6..8b3807609ff2 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -822,7 +822,7 @@ struct hid_driver {
 			struct hid_usage *usage, __s32 value);
 	void (*report)(struct hid_device *hdev, struct hid_report *report);
 
-	__u8 *(*report_fixup)(struct hid_device *hdev, __u8 *buf,
+	const __u8 *(*report_fixup)(struct hid_device *hdev, __u8 *buf,
 			unsigned int *size);
 
 	int (*input_mapping)(struct hid_device *hdev,

-- 
2.45.2