From: Kant Fan <kant@allwinnertech.com>
To: myungjoo.ham@samsung.com, kyungmin.park@samsung.com,
cw00.choi@samsung.com
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
allwinner-opensource-support@allwinnertech.com
Subject: [RESEND] devfreq: governor: Save void *data in the governor userspace
Date: Tue, 29 Mar 2022 17:14:49 +0800 [thread overview]
Message-ID: <20220329091449.105308-1-kant@allwinnertech.com> (raw)
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(). So if a governor want to use void *data
to do some other things, it must save void *data in the init()
function and restore void *data in the exit() function.
Signed-off-by: Kant Fan <kant@allwinnertech.com>
---
drivers/devfreq/governor_userspace.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
index ab9db7adb3ad..dbbb448dcbcf 100644
--- a/drivers/devfreq/governor_userspace.c
+++ b/drivers/devfreq/governor_userspace.c
@@ -17,6 +17,7 @@
struct userspace_data {
unsigned long user_frequency;
bool valid;
+ void *saved_data;
};
static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
@@ -91,6 +92,7 @@ static int userspace_init(struct devfreq *devfreq)
goto out;
}
data->valid = false;
+ data->saved_data = devfreq->data;
devfreq->data = data;
err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
@@ -100,6 +102,8 @@ static int userspace_init(struct devfreq *devfreq)
static void userspace_exit(struct devfreq *devfreq)
{
+ struct userspace_data *data = devfreq->data;
+ void *saved_data = data->saved_data;
/*
* Remove the sysfs entry, unless this is being called after
* device_del(), which should have done this already via kobject_del().
@@ -108,7 +112,7 @@ static void userspace_exit(struct devfreq *devfreq)
sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
kfree(devfreq->data);
- devfreq->data = NULL;
+ devfreq->data = saved_data;
}
static int devfreq_userspace_handler(struct devfreq *devfreq,
--
2.29.0
next reply other threads:[~2022-03-29 9:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-29 9:14 Kant Fan [this message]
2022-09-14 9:15 ` [RESEND] devfreq: governor: Save void *data in the governor userspace Kant Fan
[not found] ` <CGME20220914091525epcas1p31c8a9b11ba7a36da4678e3254b0ea962@epcms1p8>
2022-09-14 9:43 ` MyungJoo Ham
2022-09-15 7:41 ` Kant Fan
2022-09-21 13:15 ` Kant Fan
2022-09-26 9:50 ` MyungJoo Ham
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