linux-kernel - Re: [PATCH v4] PM/devfreq: governor: Add a private governor

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Date:   Sun, 20 Nov 2022 20:50:44 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Kant Fan <kant@...winnertech.com>, myungjoo.ham@...sung.com,
        kyungmin.park@...sung.com, cw00.choi@...sung.com,
        mturquette@...com, rjw@...ysocki.net, khilman@...com
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v4] PM/devfreq: governor: Add a private governor_data for
 governor

On 22. 10. 25. 16:21, 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")
> Cc: stable@...r.kernel.org # 5.10+
> Reviewed-by: Chanwoo Choi <cwchoi00@...il.com>
> Acked-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> Signed-off-by: Kant Fan <kant@...winnertech.com>
> ---
>  drivers/devfreq/devfreq.c            |  6 ++----
>  drivers/devfreq/governor_userspace.c | 12 ++++++------
>  include/linux/devfreq.h              |  7 ++++---
>  3 files changed, 12 insertions(+), 13 deletions(-)
> 


(snip)

Applied it. Thanks.

-- 
Best Regards,
Samsung Electronics
Chanwoo Choi