linux-kernel - [PATCH] thermal: create softlink by name for thermal_zone and cooling

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Message-Id: <20191015061349.141448-1-wvw@google.com>
Date:   Mon, 14 Oct 2019 23:13:49 -0700
From:   Wei Wang <wvw@...gle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     wei.vince.wang@...il.com, Wei Wang <wvw@...gle.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] thermal: create softlink by name for thermal_zone and cooling_device

The paths thermal_zone%d and cooling_device%d are not intuitive and the
numbers are subject to change due to device tree change. This usually
leads to tree traversal in userspace code.
The patch creates `tz-by-name' and `cdev-by-name' for thermal zone and
cooling_device respectively.

Signed-off-by: Wei Wang <wvw@...gle.com>
---
 drivers/thermal/thermal_core.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index d4481cc8958f..0ff8fb1d7b0a 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -22,6 +22,7 @@
 #include <net/netlink.h>
 #include <net/genetlink.h>
 #include <linux/suspend.h>
+#include <linux/kobject.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/thermal.h>
@@ -46,6 +47,8 @@ static DEFINE_MUTEX(poweroff_lock);
 
 static atomic_t in_suspend;
 static bool power_off_triggered;
+static struct kobject *cdev_link_kobj;
+static struct kobject *tz_link_kobj;
 
 static struct thermal_governor *def_governor;
 
@@ -954,7 +957,7 @@ __thermal_cooling_device_register(struct device_node *np,
 	struct thermal_zone_device *pos = NULL;
 	int result;
 
-	if (type && strlen(type) >= THERMAL_NAME_LENGTH)
+	if (!type || !type[0] || strlen(type) >= THERMAL_NAME_LENGTH)
 		return ERR_PTR(-EINVAL);
 
 	if (!ops || !ops->get_max_state || !ops->get_cur_state ||
@@ -989,9 +992,15 @@ __thermal_cooling_device_register(struct device_node *np,
 		return ERR_PTR(result);
 	}
 
-	/* Add 'this' new cdev to the global cdev list */
+	/* Add 'this' new cdev to the global cdev list and create link*/
 	mutex_lock(&thermal_list_lock);
 	list_add(&cdev->node, &thermal_cdev_list);
+	if (!cdev_link_kobj)
+		cdev_link_kobj = kobject_create_and_add("cdev-by-name",
+						cdev->device.kobj.parent);
+	if (!cdev_link_kobj || sysfs_create_link(cdev_link_kobj,
+						&cdev->device.kobj, cdev->type))
+		dev_err(&cdev->device, "Failed to create cdev-by-name link\n");
 	mutex_unlock(&thermal_list_lock);
 
 	/* Update binding information for 'this' new cdev */
@@ -1157,6 +1166,8 @@ void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
 			}
 		}
 	}
+	if (cdev_link_kobj)
+		sysfs_remove_link(cdev_link_kobj, cdev->type);
 
 	mutex_unlock(&thermal_list_lock);
 
@@ -1340,6 +1351,12 @@ thermal_zone_device_register(const char *type, int trips, int mask,
 
 	mutex_lock(&thermal_list_lock);
 	list_add_tail(&tz->node, &thermal_tz_list);
+	if (!tz_link_kobj)
+		tz_link_kobj = kobject_create_and_add("tz-by-name",
+						tz->device.kobj.parent);
+	if (!tz_link_kobj || sysfs_create_link(tz_link_kobj,
+						&tz->device.kobj, tz->type))
+		dev_err(&tz->device, "Failed to create tz-by-name link\n");
 	mutex_unlock(&thermal_list_lock);
 
 	/* Bind cooling devices for this zone */
@@ -1411,6 +1428,8 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 			}
 		}
 	}
+	if (tz_link_kobj)
+		sysfs_remove_link(tz_link_kobj, tz->type);
 
 	mutex_unlock(&thermal_list_lock);
 
-- 
2.23.0.700.g56cf767bdb-goog