hwmon: (asus_atk0110) Don't load if ACPI resources aren't enforced

When the user passes the kernel parameter acpi_enforce_resources=lax,
the ACPI resources are no longer protected, so a native driver can
make use of them. In that case, we do not want the asus_atk0110 to be
loaded. Unfortunately, this driver loads automatically due to its
MODULE_DEVICE_TABLE, so the user ends up with two drivers loaded for
the same device - this is bad.

So I suggest that we prevent the asus_atk0110 driver from loading if
acpi_enforce_resources=lax.
Signed-off-by: NJean Delvare <khali@linux-fr.org>
Acked-by: NLuca Tettamanti <kronos.it@gmail.com>
Cc: Len Brown <lenb@kernel.org>

drivers/acpi/osl.c

@@ -1206,6 +1206,15 @@ int acpi_check_mem_region(resource_size_t start, resource_size_t n,
 }
 EXPORT_SYMBOL(acpi_check_mem_region);
 
+/*
+ * Let drivers know whether the resource checks are effective
+ */
+int acpi_resources_are_enforced(void)
+{
+	return acpi_enforce_resources == ENFORCE_RESOURCES_STRICT;
+}
+EXPORT_SYMBOL(acpi_resources_are_enforced);
+
 /*
  * Acquire a spinlock.
  *

drivers/hwmon/asus_atk0110.c

@@ -1411,6 +1411,13 @@ static int __init atk0110_init(void)
 {
 	int ret;
 
+	/* Make sure it's safe to access the device through ACPI */
+	if (!acpi_resources_are_enforced()) {
+		pr_err("atk: Resources not safely usable due to "
+		       "acpi_enforce_resources kernel parameter\n");
+		return -EBUSY;
+	}
+
 	ret = acpi_bus_register_driver(&atk_driver);
 	if (ret)
 		pr_info("atk: acpi_bus_register_driver failed: %d\n", ret);

include/linux/acpi.h

@@ -248,6 +248,8 @@ int acpi_check_region(resource_size_t start, resource_size_t n,
 int acpi_check_mem_region(resource_size_t start, resource_size_t n,
 		      const char *name);
 
+int acpi_resources_are_enforced(void);
+
 #ifdef CONFIG_PM_SLEEP
 void __init acpi_no_s4_hw_signature(void);
 void __init acpi_old_suspend_ordering(void);