linux-kernel - [PATCH 4/5] platform/x86: dell-ddv: Add "force" module param

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Message-Id: <20230126194021.381092-5-W_Armin@gmx.de>
Date:   Thu, 26 Jan 2023 20:40:20 +0100
From:   Armin Wolf <W_Armin@....de>
To:     hdegoede@...hat.com, markgross@...nel.org
Cc:     jdelvare@...e.com, linux@...ck-us.net,
        platform-driver-x86@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] platform/x86: dell-ddv: Add "force" module param

Until now, the dell-wmi-ddv driver needs to be manually
patched and compiled to test compatibility with unknown
DDV WMI interface versions.
Add a module param to allow users to force loading even
when a unknown interface version was detected. Since this
might cause various unwanted side effects, the module param
is marked as unsafe.
Also update kernel-parameters.txt.

Signed-off-by: Armin Wolf <W_Armin@....de>
---
 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 drivers/platform/x86/dell/dell-wmi-ddv.c        | 13 +++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6cfa6e3996cf..9bbff5113427 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1024,6 +1024,9 @@
 	dell_smm_hwmon.fan_max=
 			[HW] Maximum configurable fan speed.

+	dell_wmi_ddv.force=
+			[HW] Do not check for supported WMI interface versions.
+
 	dfltcc=		[HW,S390]
 			Format: { on | off | def_only | inf_only | always }
 			on:       s390 zlib hardware support for compression on
diff --git a/drivers/platform/x86/dell/dell-wmi-ddv.c b/drivers/platform/x86/dell/dell-wmi-ddv.c
index 58fadb74e86a..9695bf493ea6 100644
--- a/drivers/platform/x86/dell/dell-wmi-ddv.c
+++ b/drivers/platform/x86/dell/dell-wmi-ddv.c
@@ -34,6 +34,10 @@
 #define DELL_EPPID_LENGTH	20
 #define DELL_EPPID_EXT_LENGTH	23

+static bool force;
+module_param_unsafe(force, bool, 0);
+MODULE_PARM_DESC(force, "Force loading without checking for supported WMI interface versions");
+
 enum dell_ddv_method {
 	DELL_DDV_BATTERY_DESIGN_CAPACITY	= 0x01,
 	DELL_DDV_BATTERY_FULL_CHARGE_CAPACITY	= 0x02,
@@ -349,8 +353,13 @@ static int dell_wmi_ddv_probe(struct wmi_device *wdev, const void *context)
 		return ret;

 	dev_dbg(&wdev->dev, "WMI interface version: %d\n", version);
-	if (version < DELL_DDV_SUPPORTED_VERSION_MIN || version > DELL_DDV_SUPPORTED_VERSION_MAX)
-		return -ENODEV;
+	if (version < DELL_DDV_SUPPORTED_VERSION_MIN || version > DELL_DDV_SUPPORTED_VERSION_MAX) {
+		if (!force)
+			return -ENODEV;
+
+		dev_warn(&wdev->dev, "Loading despite unsupported WMI interface version (%u)\n",
+			 version);
+	}

 	data = devm_kzalloc(&wdev->dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
--
2.30.2