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From:   Daniel Lezcano <daniel.lezcano@linaro.org>
To:     daniel.lezcano@linaro.org, rafael@kernel.org
Cc:     rui.zhang@intel.com, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, Len Brown <lenb@kernel.org>,
        linux-acpi@vger.kernel.org (open list:ACPI)
Subject: [PATCH v3 5/6] thermal/drivers/acpi: Make cross dev link optional by configuration
Date:   Thu, 13 Apr 2023 13:46:46 +0200
Message-Id: <20230413114647.3878792-6-daniel.lezcano@linaro.org>
In-Reply-To: <20230413114647.3878792-1-daniel.lezcano@linaro.org>
References: <20230413114647.3878792-1-daniel.lezcano@linaro.org>
MIME-Version: 1.0
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The ACPI thermal driver creates a link in the thermal zone device
sysfs directory pointing to the device sysfs directory. At the same
time, it creates a back pointer link from the device to the thermal
zone device sysfs directory.

From a generic perspective, having a device pointer in the sysfs
thermal zone directory may make sense. But the opposite is not true as
the same driver can be related to multiple thermal zones.

The usage of these information is very specific to ACPI and it is
questionable if they are really needed.

Let's make the code optional and disable it by default. If it hurts,
we will revert this change.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/acpi/Kconfig   | 13 +++++++++
 drivers/acpi/thermal.c | 62 ++++++++++++++++++++++++++++--------------
 2 files changed, 55 insertions(+), 20 deletions(-)

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index ccbeab9500ec..7df4e18f06ef 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -336,6 +336,19 @@ config ACPI_THERMAL
 	  To compile this driver as a module, choose M here:
 	  the module will be called thermal.
 
+config ACPI_THERMAL_SYSFS_ADDON
+       bool "Enable thermal sysfs addon"
+       depends on ACPI_THERMAL
+       def_bool n
+       help
+	 Enable sysfs extra information added in the thermal zone and
+	 the driver specific sysfs directories. That could be a link
+	 to the associated thermal zone as well as a link pointing to
+	 the device from the thermal zone. By default those are
+	 disabled and are candidate for removal, if you need these
+	 information anyway, enable the option or upgrade the
+	 userspace program using them.
+
 config ACPI_PLATFORM_PROFILE
 	tristate
 
diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index 5763db4528b8..30fe189d04f8 100644
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -787,9 +787,44 @@ static struct thermal_zone_device_ops acpi_thermal_zone_ops = {
 	.critical = acpi_thermal_zone_device_critical,
 };
 
+#ifdef CONFIG_ACPI_THERMAL_SYSFS_ADDON
+static int acpi_thermal_zone_sysfs_add(struct acpi_thermal *tz)
+{
+	struct device *tzdev = thermal_zone_device(tz->thermal_zone);
+	int ret;
+	
+	ret = sysfs_create_link(&tz->device->dev.kobj,
+				&tzdev->kobj, "thermal_zone");
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_link(&tzdev->kobj,
+				   &tz->device->dev.kobj, "device");
+	if (ret)
+		sysfs_remove_link(&tz->device->dev.kobj, "thermal_zone");
+
+	return ret;
+}
+
+static void acpi_thermal_zone_sysfs_remove(struct acpi_thermal *tz)
+{
+	struct device *tzdev = thermal_zone_device(tz->thermal_zone);
+	
+	sysfs_remove_link(&tz->device->dev.kobj, "thermal_zone");
+	sysfs_remove_link(&tzdev->kobj, "device");
+}
+#else
+static inline int acpi_thermal_zone_sysfs_add(struct acpi_thermal *tz)
+{
+	return 0;
+}
+static inline void acpi_thermal_zone_sysfs_remove(struct acpi_thermal *tz)
+{
+}
+#endif
+
 static int acpi_thermal_register_thermal_zone(struct acpi_thermal *tz)
 {
-	struct device *tzdev;
 	int trips = 0;
 	int result;
 	acpi_status status;
@@ -821,23 +856,15 @@ static int acpi_thermal_register_thermal_zone(struct acpi_thermal *tz)
 	if (IS_ERR(tz->thermal_zone))
 		return -ENODEV;
 
-	tzdev = thermal_zone_device(tz->thermal_zone);
-	
-	result = sysfs_create_link(&tz->device->dev.kobj,
-				   &tzdev->kobj, "thermal_zone");
+	result = acpi_thermal_zone_sysfs_add(tz);
 	if (result)
 		goto unregister_tzd;
-
-	result = sysfs_create_link(&tzdev->kobj,
-				   &tz->device->dev.kobj, "device");
-	if (result)
-		goto remove_tz_link;
-
+	
 	status =  acpi_bus_attach_private_data(tz->device->handle,
 					       tz->thermal_zone);
 	if (ACPI_FAILURE(status)) {
 		result = -ENODEV;
-		goto remove_dev_link;
+		goto remove_links;
 	}
 
 	result = thermal_zone_device_enable(tz->thermal_zone);
@@ -851,10 +878,8 @@ static int acpi_thermal_register_thermal_zone(struct acpi_thermal *tz)
 
 acpi_bus_detach:
 	acpi_bus_detach_private_data(tz->device->handle);
-remove_dev_link:
-	sysfs_remove_link(&tzdev->kobj, "device");
-remove_tz_link:
-	sysfs_remove_link(&tz->device->dev.kobj, "thermal_zone");
+remove_links:
+	acpi_thermal_zone_sysfs_remove(tz);
 unregister_tzd:
 	thermal_zone_device_unregister(tz->thermal_zone);
 
@@ -863,10 +888,7 @@ static int acpi_thermal_register_thermal_zone(struct acpi_thermal *tz)
 
 static void acpi_thermal_unregister_thermal_zone(struct acpi_thermal *tz)
 {
-	struct device *tzdev = thermal_zone_device(tz->thermal_zone);
-	
-	sysfs_remove_link(&tz->device->dev.kobj, "thermal_zone");
-	sysfs_remove_link(&tzdev->kobj, "device");
+	acpi_thermal_zone_sysfs_remove(tz);
 	thermal_zone_device_unregister(tz->thermal_zone);
 	tz->thermal_zone = NULL;
 	acpi_bus_detach_private_data(tz->device->handle);
-- 
2.34.1