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Date: Wed, 20 May 2020 10:15:17 +0530
From: Amit Kucheria <amit.kucheria@...durent.com>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: Zhang Rui <rui.zhang@...el.com>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
LKML <linux-kernel@...r.kernel.org>,
Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [RFC][PATCH 1/5] thermal: Add support for /dev/thermal_notify
On Mon, May 4, 2020 at 11:47 PM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> This change adds an optional feature to add a new device entry
> /dev/thermal_notify.
>
> When config CONFIG_THERMAL_USER_EVENT_INTERFACE is selected, this new
> device entry is created.
>
> Thermal core or any thermal driver can use thermal_dev_send_event() interface
Do you have any particular use case in mind where a platform driver
will use this interface to send platform-specific events?
IMO, we should probably try to keep this restricted to messages from
thermal core if we are to have any hope of having a standard library
in userspace capable of parsing these thermal events.
> to send events. Each user events follows a standard format:
> - zone_id
> - event_id
> - event_data
> - reserved for future, currently 0s
>
> User space can basically:
> fd = open ("/dev/thermal_notify")
> In a loop
> read (fd)
> read and process event
>
> or
> fd = open ("/dev/thermal_notify")
> Set the fs as non blocking
> In a loop
> Use poll() and wait
> read and process event
>
> There are predefined events added to thermal.h. Based on need they can
> be extended.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
> drivers/thermal/Kconfig | 9 ++
> drivers/thermal/Makefile | 3 +
> drivers/thermal/thermal_dev_if.c | 195 +++++++++++++++++++++++++++++++
> include/linux/thermal.h | 24 ++++
> 4 files changed, 231 insertions(+)
> create mode 100644 drivers/thermal/thermal_dev_if.c
>
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index 91af271e9bb0..27d05d62458e 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -78,6 +78,15 @@ config THERMAL_WRITABLE_TRIPS
> Say 'Y' here if you would like to allow userspace tools to
> change trip temperatures.
>
> +config THERMAL_USER_EVENT_INTERFACE
> + bool "Allow user space to read thermal events from a dev file"
> + help
> + This option allows a user space program to read thermal events
> + via /dev/thermal_notify file.
> +
> + Say 'Y' here if you would like to allow userspace programs to
> + read thermal events.
> +
> choice
> prompt "Default Thermal governor"
> default THERMAL_DEFAULT_GOV_STEP_WISE
> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index 8c8ed7b79915..8f65832d755a 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -11,6 +11,9 @@ thermal_sys-y += thermal_core.o thermal_sysfs.o \
> thermal_sys-$(CONFIG_THERMAL_HWMON) += thermal_hwmon.o
> thermal_sys-$(CONFIG_THERMAL_OF) += of-thermal.o
>
> +# Thermal user space events
> +obj-$(CONFIG_THERMAL_USER_EVENT_INTERFACE) += thermal_dev_if.o
> +
> # governors
> thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE) += fair_share.o
> thermal_sys-$(CONFIG_THERMAL_GOV_BANG_BANG) += gov_bang_bang.o
> diff --git a/drivers/thermal/thermal_dev_if.c b/drivers/thermal/thermal_dev_if.c
> new file mode 100644
> index 000000000000..763bfe9eef9d
> --- /dev/null
> +++ b/drivers/thermal/thermal_dev_if.c
> @@ -0,0 +1,195 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Thermal device file interface
> + * Copyright (c) 2020, Intel Corporation.
> + * All rights reserved.
> + *
> + * Author: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> + */
> +
> +#include <linux/init.h>
> +#include <linux/kfifo.h>
> +#include <linux/miscdevice.h>
> +#include <linux/poll.h>
> +#include <linux/slab.h>
> +#include <linux/thermal.h>
> +#include <linux/wait.h>
> +
> +#define THERMAL_DEV_FIFO_SIZE 1024
> +
> +struct thermal_chdev_sample {
> + int zone_id;
> + int event;
> + u64 event_data;
> + u64 reserved;
> +};
> +
> +struct thermal_chdev {
> + struct miscdevice therm_dev;
> + struct kfifo data_fifo;
> + unsigned long misc_opened;
> + wait_queue_head_t wait;
> +};
> +
> +static DEFINE_MUTEX(thermal_chdev_mutex);
> +static struct thermal_chdev *thermal_chdev;
> +
> +static int thermal_chdev_open(struct inode *inode, struct file *file)
> +{
> + struct thermal_chdev *chdev;
> +
> + chdev = container_of(file->private_data, struct thermal_chdev, therm_dev);
> +
> + /* We essentially have single reader and writer */
> + if (test_and_set_bit(0, &chdev->misc_opened))
> + return -EBUSY;
> +
> + return stream_open(inode, file);
> +}
> +
> +static int thermal_chdev_release(struct inode *inode, struct file *file)
> +{
> + struct thermal_chdev *chdev;
> +
> + chdev = container_of(file->private_data, struct thermal_chdev, therm_dev);
> +
> + clear_bit(0, &chdev->misc_opened);
> +
> + return 0;
> +}
> +
> +static __poll_t thermal_chdev_poll(struct file *file, struct poll_table_struct *wait)
> +{
> + struct thermal_chdev *chdev;
> + __poll_t mask = 0;
> +
> + chdev = container_of(file->private_data, struct thermal_chdev, therm_dev);
> +
> + poll_wait(file, &chdev->wait, wait);
> +
> + if (!kfifo_is_empty(&chdev->data_fifo))
> + mask = EPOLLIN | EPOLLRDNORM;
> +
> + return mask;
> +}
> +
> +static ssize_t thermal_chdev_read(struct file *file, char __user *buf, size_t count, loff_t *f_ps)
> +{
> + struct thermal_chdev *chdev;
> + unsigned int copied;
> + int ret;
> +
> + chdev = container_of(file->private_data, struct thermal_chdev, therm_dev);
> +
> + if (count < sizeof(struct thermal_chdev_sample))
> + return -EINVAL;
> +
> + do {
> + if (kfifo_is_empty(&chdev->data_fifo)) {
> + if (file->f_flags & O_NONBLOCK)
> + return -EAGAIN;
> +
> + ret = wait_event_interruptible(chdev->wait, !kfifo_is_empty(&chdev->data_fifo));
> + if (ret)
> + return ret;
> + }
> + ret = kfifo_to_user(&chdev->data_fifo, buf, count, &copied);
> + if (ret)
> + return ret;
> +
> + } while (copied == 0);
> +
> + return copied;
> +}
> +
> +static int thermal_chdev_capture_sample(struct thermal_chdev *chdev, struct thermal_chdev_sample *sample)
> +{
> + int ret = 0;
> +
> + if (!test_bit(0, &chdev->misc_opened))
> + return 0;
> +
> + mutex_lock(&thermal_chdev_mutex);
> + if (kfifo_avail(&chdev->data_fifo) >= sizeof(*sample)) {
> + kfifo_in(&chdev->data_fifo, (unsigned char *)sample, sizeof(*sample));
> + wake_up(&chdev->wait);
> + } else {
> + ret = -ENOMEM;
> + }
> + mutex_unlock(&thermal_chdev_mutex);
> +
> + return ret;
> +}
> +
> +static const struct file_operations thermal_chdev_fops = {
> + .open = thermal_chdev_open,
> + .read = thermal_chdev_read,
> + .release = thermal_chdev_release,
> + .poll = thermal_chdev_poll,
> + .llseek = noop_llseek,
> +};
> +
> +static int thermal_dev_if_add(void)
> +{
> + int ret;
> +
> + if (thermal_chdev)
> + return 0;
> +
> + thermal_chdev = kzalloc(sizeof(*thermal_chdev), GFP_KERNEL);
> + if (!thermal_chdev)
> + return -ENOMEM;
> +
> + ret = kfifo_alloc(&thermal_chdev->data_fifo, THERMAL_DEV_FIFO_SIZE, GFP_KERNEL);
> + if (ret)
> + goto free_mem;
> +
> + init_waitqueue_head(&thermal_chdev->wait);
> +
> + thermal_chdev->therm_dev.minor = MISC_DYNAMIC_MINOR;
> + thermal_chdev->therm_dev.name = "thermal_notify";
> + thermal_chdev->therm_dev.fops = &thermal_chdev_fops;
> + ret = misc_register(&thermal_chdev->therm_dev);
> + if (ret) {
> + kfifo_free(&thermal_chdev->data_fifo);
> + goto free_mem;
> + }
> +
> + return 0;
> +
> +free_mem:
> + kfree(thermal_chdev);
> + thermal_chdev = NULL;
> + return ret;
> +}
> +
> +/**
> + * thermal_dev_send_event() - Send thermal event to user space
> + * @zone_id: Zone id of the caller
> + * @event: A predefined thermal event
> + * @event_data: Event specific data
> + *
> + * An interface to send event to user space with an optional associated
> + * data.
> + *
> + * Return: 0 on success, other values on error.
> + */
> +int thermal_dev_send_event(int zone_id, enum thermal_device_events event, u64 event_data)
> +{
> + struct thermal_chdev_sample sample;
> +
> + if (!thermal_chdev) {
> + int ret;
> +
> + ret = thermal_dev_if_add();
> + if (ret)
> + return ret;
> + }
> +
> + sample.zone_id = zone_id;
> + sample.event = event;
> + sample.event_data = event_data;
> + sample.reserved = 0;
> + return thermal_chdev_capture_sample(thermal_chdev, &sample);
> +}
> +EXPORT_SYMBOL_GPL(thermal_dev_send_event);
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index c91b1e344d56..f5e1e7c6a9a2 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -543,4 +543,28 @@ static inline void thermal_notify_framework(struct thermal_zone_device *tz,
> { }
> #endif /* CONFIG_THERMAL */
>
> +enum thermal_device_events {
> + THERMAL_TEMP_SAMPLE = 0,
> + THERMAL_ZONE_CREATE,
> + THERMAL_ZONE_DELETE,
> + THERMAL_ZONE_DISABLED,
> + THERMAL_ZONE_ENABLED,
> + THERMAL_TEMP_LOW_THRES,
> + THERMAL_TEMP_HIGH_THRES,
> + THERMAL_TRIP_ADD,
> + THERMAL_TRIP_DELETE,
> + THERMAL_TRIP_UPDATE,
> + THERMAL_TRIP_REACHED,
> + THERMAL_PERF_CHANGED,
> +};
> +
> +#ifdef CONFIG_THERMAL_USER_EVENT_INTERFACE
> +int thermal_dev_send_event(int zone_id, enum thermal_device_events event, u64 event_data);
> +#else
> +int thermal_dev_send_event(int zone_id, enum thermal_device_events event, u64 event_data)
> +{
> + return 0;
> +}
> +#endif
> +
> #endif /* __THERMAL_H__ */
> --
> 2.25.4
>
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