linux-kernel - Re: [RFC][PATCH] thermal: add sysfs

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Date:	Wed, 24 Feb 2016 20:24:09 +0000
From:	"Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"srikars@...dia.com" <srikars@...dia.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [RFC][PATCH] thermal: add sysfs_notify on some attributes

On Tue, 2016-02-23 at 20:11 -0800, Srikar Srimath Tirumala wrote:
> Add a sysfs_notify on thermal_zone*/temp and cooling_device*/
> cur_state whenever a passive or critical trip is triggered.
> 
> This change allows usermode apps to register itself to get notified,
> when certain thermal conditions occur and reduce their workload.
> This workload throttling can reduce\prevent throttling of hardware
> clocks while allowing some other critical apps to run longer
> reliably.
> Signed-off-by: Srikar Srimath Tirumala <srikars@...dia.com>
> ---
>  drivers/thermal/thermal_core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/thermal/thermal_core.c
> b/drivers/thermal/thermal_core.c
> index a0a8fd1..d8d257d 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -567,6 +567,8 @@ void thermal_zone_device_update(struct
> thermal_zone_device *tz)
>  
>  	for (count = 0; count < tz->trips; count++)
>  		handle_thermal_trip(tz, count);
> +
> +	sysfs_notify(&tz->device.kobj, NULL, "temp");
When user space governor is used this will result in two notifications
to user space.
Also you want when a trip is violated. For some driver there will be
too many calls from irq thread, so you may want in handle_thermal_trip
when a trip is violated.

Thanks,
Srinivas
>  }
>  EXPORT_SYMBOL_GPL(thermal_zone_device_update);
>  
> @@ -1638,6 +1640,7 @@ void thermal_cdev_update(struct
> thermal_cooling_device *cdev)
>  	cdev->updated = true;
>  	trace_cdev_update(cdev, target);
>  	dev_dbg(&cdev->device, "set to state %lu\n", target);
> +	sysfs_notify(&cdev->device.kobj, NULL, "cur_state");
>  }
>  EXPORT_SYMBOL(thermal_cdev_update);
>