linux-kernel - Re: [PATCH v3 3/3] thermal: create softlink by name for thermal_zone and cooling

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Date:   Fri, 6 Dec 2019 11:15:45 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Wei Wang <wvw@...gle.com>
Cc:     wei.vince.wang@...il.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,
        Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [PATCH v3 3/3] thermal: create softlink by name for thermal_zone
 and cooling_device

On Wed, Dec 04, 2019 at 11:19:53PM -0800, Wei Wang wrote:
> 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.

This is useful, especially for systems with plenty of thermal zones :)

> Signed-off-by: Wei Wang <wvw@...gle.com>
> Reviewed-by: Amit Kucheria <amit.kucheria@...aro.org>
> ---
>  drivers/thermal/thermal_core.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 9db7f72e70f8..7872bd527f3f 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;
>  
> @@ -999,9 +1002,15 @@ __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 */
> @@ -1167,6 +1176,8 @@ 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);
>  
> @@ -1354,6 +1365,12 @@ 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 */
> @@ -1425,6 +1442,8 @@ 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);
>  

Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
Tested-by: Matthias Kaehlcke <mka@...omium.org>