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SubjectRe: [RFC][PATCH 4/5] thermal: Add support for setting polling interval
On Mon, May 4, 2020 at 11:47 PM Srinivas Pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
> Add new attribute in the thermal syfs for setting temperature sampling
> interval when CONFIG_THERMAL_USER_EVENT_INTERFACE is defined. The default
> value is 0, which means no polling.
>
> At this interval user space will get an event THERMAL_TEMP_SAMPLE with
> temperature sample. This reuses existing polling mecahnism when polling
> or passive delay is specified during zone registry. To avoid interference
> with passive and polling delay, this new polling attribute can't be used
> for those zones.

Why should the kernel periodically emit events for userspace when the
userspace is perfectly capable of deciding how frequently it wants to
poll a file for changes?

>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> ---
> drivers/thermal/thermal_core.c | 7 +++++++
> drivers/thermal/thermal_sysfs.c | 36 +++++++++++++++++++++++++++++++--
> include/linux/thermal.h | 1 +
> 3 files changed, 42 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 14770d882d42..17cd799b0073 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -313,6 +313,8 @@ static void monitor_thermal_zone(struct thermal_zone_device *tz)
> thermal_zone_device_set_polling(tz, tz->passive_delay);
> else if (tz->polling_delay)
> thermal_zone_device_set_polling(tz, tz->polling_delay);
> + else if (tz->temp_polling_delay)
> + thermal_zone_device_set_polling(tz, tz->temp_polling_delay);
> else
> thermal_zone_device_set_polling(tz, 0);
>
> @@ -446,6 +448,11 @@ static void update_temperature(struct thermal_zone_device *tz)
> tz->temperature = temp;
> mutex_unlock(&tz->lock);
>
> + if (tz->temp_polling_delay) {
> + thermal_dev_send_event(tz->id, THERMAL_TEMP_SAMPLE, temp);
> + monitor_thermal_zone(tz);
> + }
> +
> trace_thermal_temperature(tz);
> if (tz->last_temperature == THERMAL_TEMP_INVALID)
> dev_dbg(&tz->device, "last_temperature N/A, current_temperature=%d\n",
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index aa85424c3ac4..0df7997993fe 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -248,6 +248,36 @@ create_thres_attr(temp_thres_low);
> create_thres_attr(temp_thres_high);
> create_thres_attr(temp_thres_hyst);
>
> +static ssize_t
> +temp_polling_delay_store(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct thermal_zone_device *tz = to_thermal_zone(dev);
> + int val;
> +
> + if (kstrtoint(buf, 10, &val))
> + return -EINVAL;
> +
> + if (val && val < 1000)
> + return -EINVAL;
> +
> + tz->temp_polling_delay = val;
> + thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
> +
> + return count;
> +}
> +
> +static ssize_t
> +temp_polling_delay_show(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + struct thermal_zone_device *tz = to_thermal_zone(dev);
> +
> + return sprintf(buf, "%d\n", tz->temp_polling_delay);
> +}
> +
> +static DEVICE_ATTR_RW(temp_polling_delay);
> +
> static int create_user_events_attrs(struct thermal_zone_device *tz)
> {
> struct attribute **attrs;
> @@ -260,8 +290,8 @@ static int create_user_events_attrs(struct thermal_zone_device *tz)
> if (tz->ops->get_temp_thres_high)
> ++index;
>
> - /* One additional space for NULL */
> - attrs = kcalloc(index + 1, sizeof(*attrs), GFP_KERNEL);
> + /* One additional space for NULL and temp_pollling_delay */
> + attrs = kcalloc(index + 2, sizeof(*attrs), GFP_KERNEL);
> if (!attrs)
> return -ENOMEM;
>
> @@ -312,6 +342,8 @@ static int create_user_events_attrs(struct thermal_zone_device *tz)
> attrs[index] = &tz->threshold_attrs[index].attr.attr;
> ++index;
> }
> + if (!tz->polling_delay && !tz->passive_delay)
> + attrs[index++] = &dev_attr_temp_polling_delay.attr;
> attrs[index] = NULL;
> tz->threshold_attribute_group.attrs = attrs;
>
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index ee9d79ace7ce..0ec4bd8c9c5c 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -216,6 +216,7 @@ struct thermal_zone_device {
> enum thermal_notify_event notify_event;
> struct attribute_group threshold_attribute_group;
> struct thermal_attr *threshold_attrs;
> + int temp_polling_delay;
> };
>
> /**
> --
> 2.25.4
>

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