platform/x86: asus-wmi: export symbols used for read/write WMI

Export symbols for reading/writing WMI symbols using a namespace.
Existing functions:
- asus_wmi_evaluate_method
- asus_wmi_set_devstate
New function:
- asus_wmi_get_devstate_dsts

The new function is intended for use with DSTS WMI method only and
avoids requiring the asus_wmi driver data to select the WMI method.

Co-developed-by: Denis Benato <[e-mail]>
Signed-off-by: Denis Benato <[e-mail]>
Signed-off-by: Luke D. Jones <[e-mail]>
Reviewed-by: Mario Limonciello <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

drivers/platform/x86/asus-wmi.c

···
 {
 	return asus_wmi_evaluate_method3(method_id, arg0, arg1, 0, retval);
 }
-EXPORT_SYMBOL_GPL(asus_wmi_evaluate_method);
+EXPORT_SYMBOL_NS_GPL(asus_wmi_evaluate_method, "ASUS_WMI");
 
 static int asus_wmi_evaluate_method5(u32 method_id,
 		u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4, u32 *retval)
···
 	return 0;
 }
 
-int asus_wmi_set_devstate(u32 dev_id, u32 ctrl_param,
-				 u32 *retval)
+/**
+ * asus_wmi_get_devstate_dsts() - Get the WMI function state.
+ * @dev_id: The WMI method ID to call.
+ * @retval: A pointer to where to store the value returned from WMI.
+ *
+ * Returns:
+ * * %-ENODEV	- method ID is unsupported.
+ * * %0			- successful and retval is filled.
+ * * %other		- error from WMI call.
+ */
+int asus_wmi_get_devstate_dsts(u32 dev_id, u32 *retval)
+{
+	int err;
+
+	err = asus_wmi_evaluate_method(ASUS_WMI_METHODID_DSTS, dev_id, 0, retval);
+	if (err)
+		return err;
+
+	if ((*retval & ASUS_WMI_DSTS_PRESENCE_BIT) == 0x00)
+		return -ENODEV;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(asus_wmi_get_devstate_dsts, "ASUS_WMI");
+
+/**
+ * asus_wmi_set_devstate() - Set the WMI function state.
+ *
+ * Note: an asus_wmi_set_devstate() call must be paired with a
+ * asus_wmi_get_devstate_dsts() to check if the WMI function is supported.
+ *
+ * @dev_id: The WMI function to call.
+ * @ctrl_param: The argument to be used for this WMI function.
+ * @retval: A pointer to where to store the value returned from WMI.
+ *
+ * Returns:
+ * * %-ENODEV	- method ID is unsupported.
+ * * %0			- successful and retval is filled.
+ * * %other		- error from WMI call.
+ */
+int asus_wmi_set_devstate(u32 dev_id, u32 ctrl_param, u32 *retval)
 {
 	return asus_wmi_evaluate_method(ASUS_WMI_METHODID_DEVS, dev_id,
 					ctrl_param, retval);
 }
+EXPORT_SYMBOL_NS_GPL(asus_wmi_set_devstate, "ASUS_WMI");
 
 /* Helper for special devices with magic return codes */
 static int asus_wmi_get_devstate_bits(struct asus_wmi *asus,

include/linux/platform_data/x86/asus-wmi.h

···
 #if IS_REACHABLE(CONFIG_ASUS_WMI)
 void set_ally_mcu_hack(enum asus_ally_mcu_hack status);
 void set_ally_mcu_powersave(bool enabled);
+int asus_wmi_get_devstate_dsts(u32 dev_id, u32 *retval);
 int asus_wmi_set_devstate(u32 dev_id, u32 ctrl_param, u32 *retval);
 int asus_wmi_evaluate_method(u32 method_id, u32 arg0, u32 arg1, u32 *retval);
 #else
···
 {
 }
 static inline int asus_wmi_set_devstate(u32 dev_id, u32 ctrl_param, u32 *retval)
+{
+	return -ENODEV;
+}
+static inline int asus_wmi_get_devstate_dsts(u32 dev_id, u32 *retval)
 {
 	return -ENODEV;
 }