Re: [PATCH v3] PM/devfreq: governor: Add a private governor_data for governor

[Kant Fan]

On 10/22/2022 7:41 AM, Chanwoo Choi wrote:
> Hi,
>
> Looks good to me. But, you need to send it to the stable mailing list
> too as I commented on previous mail.
>
> Please add stable@xxxxxxxxxxxxxxx to Cc.

Hi Chanwoo,
Thanks for the notice. Please review this patch-v4 [1].

[1]
https://lore.kernel.org/all/20221025072109.64025-1-kant@xxxxxxxxxxxxxxxxx/

--
Best Regards,
Kant Fan

> On 22. 10. 14. 18:43, Kant Fan wrote:
> > The member void *data in the structure devfreq can be overwrite
> > by governor_userspace. For example:
> > 1. The device driver assigned the devfreq governor to simple_ondemand
> > by the function devfreq_add_device() and init the devfreq member
> > void *data to a pointer of a static structure devfreq_simple_ondemand_data
> > by the function devfreq_add_device().
> > 2. The user changed the devfreq governor to userspace by the command
> > "echo userspace > /sys/class/devfreq/.../governor".
> > 3. The governor userspace alloced a dynamic memory for the struct
> > userspace_data and assigend the member void *data of devfreq to
> > this memory by the function userspace_init().
> > 4. The user changed the devfreq governor back to simple_ondemand
> > by the command "echo simple_ondemand > /sys/class/devfreq/.../governor".
> > 5. The governor userspace exited and assigned the member void *data
> > in the structure devfreq to NULL by the function userspace_exit().
> > 6. The governor simple_ondemand fetched the static information of
> > devfreq_simple_ondemand_data in the function
> > devfreq_simple_ondemand_func() but the member void *data of devfreq was
> > assigned to NULL by the function userspace_exit().
> > 7. The information of upthreshold and downdifferential is lost
> > and the governor simple_ondemand can't work correctly.
> >
> > The member void *data in the structure devfreq is designed for
> > a static pointer used in a governor and inited by the function
> > devfreq_add_device(). This patch add an element named governor_data
> > in the devfreq structure which can be used by a governor(E.g userspace)
> > who want to assign a private data to do some private things.
> >
> > Fixes: ce26c5bb9569 ("PM / devfreq: Add basic governors")
> >
> > Acked-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> >
> > Signed-off-by: Kant Fan <kant@xxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/devfreq/devfreq.c            |  6 ++----
> >   drivers/devfreq/governor_userspace.c | 12 ++++++------
> >   include/linux/devfreq.h              |  7 ++++---
> >   3 files changed, 12 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > index 63347a5ae599..8c5f6f7fca11 100644
> > --- a/drivers/devfreq/devfreq.c
> > +++ b/drivers/devfreq/devfreq.c
> > @@ -776,8 +776,7 @@ static void remove_sysfs_files(struct devfreq *devfreq,
> >    * @dev:	the device to add devfreq feature.
> >    * @profile:	device-specific profile to run devfreq.
> >    * @governor_name:	name of the policy to choose frequency.
> > - * @data:	private data for the governor. The devfreq framework does not
> > - *		touch this value.
> > + * @data:	devfreq driver pass to governors, governor should not change it.
> >    */
> >   struct devfreq *devfreq_add_device(struct device *dev,
> >   				   struct devfreq_dev_profile *profile,
> > @@ -1011,8 +1010,7 @@ static void devm_devfreq_dev_release(struct device *dev, void *res)
> >    * @dev:	the device to add devfreq feature.
> >    * @profile:	device-specific profile to run devfreq.
> >    * @governor_name:	name of the policy to choose frequency.
> > - * @data:	private data for the governor. The devfreq framework does not
> > - *		touch this value.
> > + * @data:	 devfreq driver pass to governors, governor should not change it.
> >    *
> >    * This function manages automatically the memory of devfreq device using device
> >    * resource management and simplify the free operation for memory of devfreq
> > diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
> > index ab9db7adb3ad..d69672ccacc4 100644
> > --- a/drivers/devfreq/governor_userspace.c
> > +++ b/drivers/devfreq/governor_userspace.c
> > @@ -21,7 +21,7 @@ struct userspace_data {
> >   
> >   static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
> >   {
> > -	struct userspace_data *data = df->data;
> > +	struct userspace_data *data = df->governor_data;
> >   
> >   	if (data->valid)
> >   		*freq = data->user_frequency;
> > @@ -40,7 +40,7 @@ static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
> >   	int err = 0;
> >   
> >   	mutex_lock(&devfreq->lock);
> > -	data = devfreq->data;
> > +	data = devfreq->governor_data;
> >   
> >   	sscanf(buf, "%lu", &wanted);
> >   	data->user_frequency = wanted;
> > @@ -60,7 +60,7 @@ static ssize_t set_freq_show(struct device *dev,
> >   	int err = 0;
> >   
> >   	mutex_lock(&devfreq->lock);
> > -	data = devfreq->data;
> > +	data = devfreq->governor_data;
> >   
> >   	if (data->valid)
> >   		err = sprintf(buf, "%lu\n", data->user_frequency);
> > @@ -91,7 +91,7 @@ static int userspace_init(struct devfreq *devfreq)
> >   		goto out;
> >   	}
> >   	data->valid = false;
> > -	devfreq->data = data;
> > +	devfreq->governor_data = data;
> >   
> >   	err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
> >   out:
> > @@ -107,8 +107,8 @@ static void userspace_exit(struct devfreq *devfreq)
> >   	if (devfreq->dev.kobj.sd)
> >   		sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
> >   
> > -	kfree(devfreq->data);
> > -	devfreq->data = NULL;
> > +	kfree(devfreq->governor_data);
> > +	devfreq->governor_data = NULL;
> >   }
> >   
> >   static int devfreq_userspace_handler(struct devfreq *devfreq,
> > diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> > index 34aab4dd336c..4dc7cda4fd46 100644
> > --- a/include/linux/devfreq.h
> > +++ b/include/linux/devfreq.h
> > @@ -152,8 +152,8 @@ struct devfreq_stats {
> >    * @max_state:		count of entry present in the frequency table.
> >    * @previous_freq:	previously configured frequency value.
> >    * @last_status:	devfreq user device info, performance statistics
> > - * @data:	Private data of the governor. The devfreq framework does not
> > - *		touch this.
> > + * @data:	devfreq driver pass to governors, governor should not change it.
> > + * @governor_data:	private data for governors, devfreq core doesn't touch it.
> >    * @user_min_freq_req:	PM QoS minimum frequency request from user (via sysfs)
> >    * @user_max_freq_req:	PM QoS maximum frequency request from user (via sysfs)
> >    * @scaling_min_freq:	Limit minimum frequency requested by OPP interface
> > @@ -193,7 +193,8 @@ struct devfreq {
> >   	unsigned long previous_freq;
> >   	struct devfreq_dev_status last_status;
> >   
> > -	void *data; /* private data for governors */
> > +	void *data;
> > +	void *governor_data;
> >   
> >   	struct dev_pm_qos_request user_min_freq_req;
> >   	struct dev_pm_qos_request user_max_freq_req;