linux-kernel - Re: [PATCH] PM / devfreq: Add new name attribute for sysfs

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Date:   Thu, 30 Aug 2018 07:59:43 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc:     myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        rafael.j.wysocki@...el.com, chanwoo@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] PM / devfreq: Add new name attribute for sysfs

Hi Bartlomiej,

On 2018년 08월 29일 21:50, Bartlomiej Zolnierkiewicz wrote:
> 
> Hi Chanwoo,
> 
> On Wednesday, August 29, 2018 04:34:06 PM Chanwoo Choi wrote:
>> commit 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for
>> sysfs") changed the node name to devfreq(x). After this commit, it is not
>> possible to get the device name through /sys/class/devfreq/devfreq(X)/*.
>>
>> Add new name attribute in order to get device name.
> 
> Could you please describe the issue encountered in more detail
> (what the old device name is needed for)?

You can check it on mail thread[1].
[1] https://lkml.org/lkml/2018/5/8/1042

>  
>> Cc: stable@...r.kernel.org
>> Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
>> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
>> ---
>>  drivers/devfreq/devfreq.c | 11 +++++++++++
>>  include/linux/devfreq.h   |  3 +++
>>  2 files changed, 14 insertions(+)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 4c49bb1330b5..2145563d5ee5 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -620,6 +620,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  	}
>>  	devfreq->max_freq = devfreq->scaling_max_freq;
>>
>> +	devfreq->name = dev_name(devfreq->dev.parent);
> 
> It seems that 'dev' can be used instead of 'devfreq->dev.parent'.

devfreq->dev.parent is same with dev. it doesn't matter.

> 
>> +	if (IS_ERR_OR_NULL(devfreq->name))
> 
> Error values are not encoded into pointer returned by dev_name()
> (drivers/base/ code is only checking for pointer being NULL).

OK. I'll just check whether NULL or not.

> 
>> +		return -EINVAL;
> 
> This leaks 'devfreq' object and doesn't encode return value into
> pointer returned by devfreq_add_device(), it should be replaced by:

Right. I'll fix it.

> 
> 	err = -EINVAL;
> 	goto err_dev;
> 
>>  	dev_set_name(&devfreq->dev, "devfreq%d",
>>  				atomic_inc_return(&devfreq_no));
>>  	err = device_register(&devfreq->dev);
> 
> Best regards,
> --
> Bartlomiej Zolnierkiewicz
> Samsung R&D Institute Poland
> Samsung Electronics
> 
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics