[PATCH v3] PM / devfreq: Add new name attribute for sysfs

[PATCH v3] PM / devfreq: Add new name attribute for sysfs

[Chanwoo Choi]

The 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.

Cc: stable@vger.kernel.org
Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
---
 Changes from v2:
- Change the order of name_show() according to the sequence in devfreq_attrs[]

Changes from v1:
- Update sysfs-class-devfreq documentation
- Show device name directly from 'devfreq->dev.parent'

Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
 drivers/devfreq/devfreq.c                     | 9 +++++++++
 2 files changed, 16 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
index 01196e19afca..75897e2fde43 100644
--- a/Documentation/ABI/testing/sysfs-class-devfreq
+++ b/Documentation/ABI/testing/sysfs-class-devfreq
@@ -7,6 +7,13 @@ Description:
 		The name of devfreq object denoted as ... is same as the
 		name of device using devfreq.
 
+What:		/sys/class/devfreq/.../name
+Date:		November 2019
+Contact:	Chanwoo Choi <cw00.choi@samsung.com>
+Description:
+		The /sys/class/devfreq/.../name shows the name of device
+		of the corresponding devfreq object.
+
 What:		/sys/class/devfreq/.../governor
 Date:		September 2011
 Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 65a4b6cf3fa5..6f4d93d2a651 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -1169,6 +1169,14 @@ int devfreq_remove_governor(struct devfreq_governor *governor)
 }
 EXPORT_SYMBOL(devfreq_remove_governor);
 
+static ssize_t name_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct devfreq *devfreq = to_devfreq(dev);
+	return sprintf(buf, "%s\n", dev_name(devfreq->dev.parent));
+}
+static DEVICE_ATTR_RO(name);
+
 static ssize_t governor_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
@@ -1477,6 +1485,7 @@ static ssize_t trans_stat_show(struct device *dev,
 static DEVICE_ATTR_RO(trans_stat);
 
 static struct attribute *devfreq_attrs[] = {
+	&dev_attr_name.attr,
 	&dev_attr_governor.attr,
 	&dev_attr_available_governors.attr,
 	&dev_attr_cur_freq.attr,
-- 
2.17.1

Re: [PATCH v3] PM / devfreq: Add new name attribute for sysfs

[Greg KH]

On Mon, Nov 25, 2019 at 10:03:57AM +0900, Chanwoo Choi wrote:
> The 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.
> 
> Cc: stable@vger.kernel.org
> Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
> ---
>  Changes from v2:
> - Change the order of name_show() according to the sequence in devfreq_attrs[]
> 
> Changes from v1:
> - Update sysfs-class-devfreq documentation
> - Show device name directly from 'devfreq->dev.parent'
> 

Shouldn't you just revert the original patch here?  Why did the sysfs
file change?

> Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
>  drivers/devfreq/devfreq.c                     | 9 +++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
> index 01196e19afca..75897e2fde43 100644
> --- a/Documentation/ABI/testing/sysfs-class-devfreq
> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
> @@ -7,6 +7,13 @@ Description:
>  		The name of devfreq object denoted as ... is same as the
>  		name of device using devfreq.
>  
> +What:		/sys/class/devfreq/.../name
> +Date:		November 2019
> +Contact:	Chanwoo Choi <cw00.choi@samsung.com>
> +Description:
> +		The /sys/class/devfreq/.../name shows the name of device
> +		of the corresponding devfreq object.
> +
>  What:		/sys/class/devfreq/.../governor
>  Date:		September 2011
>  Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 65a4b6cf3fa5..6f4d93d2a651 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -1169,6 +1169,14 @@ int devfreq_remove_governor(struct devfreq_governor *governor)
>  }
>  EXPORT_SYMBOL(devfreq_remove_governor);
>  
> +static ssize_t name_show(struct device *dev,
> +			struct device_attribute *attr, char *buf)
> +{
> +	struct devfreq *devfreq = to_devfreq(dev);
> +	return sprintf(buf, "%s\n", dev_name(devfreq->dev.parent));

Why is the parent's name being set here, and not the device name?

The device name should be the name of the directory, and the parent's
name is the name of the parent directory, why is a sysfs attribute for a
name needed at all?

confused,

greg k-h

Re: [PATCH v3] PM / devfreq: Add new name attribute for sysfs

[Chanwoo Choi]

Hi Greg,

On 11/25/19 5:50 PM, Greg KH wrote:
> On Mon, Nov 25, 2019 at 10:03:57AM +0900, Chanwoo Choi wrote:
>> The 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.
>>
>> Cc: stable@vger.kernel.org
>> Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> ---
>>  Changes from v2:
>> - Change the order of name_show() according to the sequence in devfreq_attrs[]
>>
>> Changes from v1:
>> - Update sysfs-class-devfreq documentation
>> - Show device name directly from 'devfreq->dev.parent'
>>
> 
> Shouldn't you just revert the original patch here?  Why did the sysfs
> file change?

The initial devfreq code used the parent device name for device name
corresponding to devfreq object instead of 'devfreq%d' style.
Before applied The commit 4585fbcb5331 ("PM / devfreq: Modify
the device name as devfreq(X) for sysfs"), the devfreq sysfs
showed the parent device name as following:

For example on Odroid-XU3 board before applied the commit 4585fbcb5331,
	/sys/class/devfreq/soc:bus_wcore
	/sys/class/devfreq/soc:bus_noc
	...(skip)


But, I think that devfreq subsystem had to show the consistent
sysfs entry name for devfreq device like input, thermal, hwmon subsystem.

For example on Odroid-XU3 board,
- The input subsystem show the 'input%d' style for input device.
$root@localhost:/# ls /sys/class/input/                                         
event0  event1  input0  input1  mice  mouse0

- The thermal subsystem show the 'cooling_device%d' style for thermal cooling device.
$ root@localhost:/# ls /sys/class/thermal/                                       
cooling_device0  cooling_device2  thermal_zone1  thermal_zone3
cooling_device1  thermal_zone0    thermal_zone2  thermal_zone4

- The hwmon subsystem show the 'hwmon%d' style for h/w monitor device.
$root@localhost:/# ls /sys/class/hwmon/                                         
hwmon0


So, I tried to make the consistent sysfs entry name for devfreq device
by contributing commit 4585fbcb5331 ("PM / devfreq: Modify the device name as
devfreq(X) for sysfs"). But, The commit 4585fbcb5331 have missed that sysfs
interface had to provide the real device name. Some subsystem like thermal
and hwmon provide the device type or device name through sysfs interface.
It is possible to make the user to find their own specific device by iteration
on user-space.

root@localhost:/# cat /sys/class/thermal/cooling_device0/type 
pwm-fan
root@localhost:/# cat /sys/class/thermal/cooling_device1/type                  
thermal-cpufreq-0
root@localhost:/# cat /sys/class/thermal/cooling_device2/type                  
thermal-cpufreq-1

root@localhost:/# cat /sys/class/hwmon/hwmon0/name                             
pwmfan


So, I add the new 'name' attribute of sysfs for devfreq device.

> 
>> Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
>>  drivers/devfreq/devfreq.c                     | 9 +++++++++
>>  2 files changed, 16 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
>> index 01196e19afca..75897e2fde43 100644
>> --- a/Documentation/ABI/testing/sysfs-class-devfreq
>> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
>> @@ -7,6 +7,13 @@ Description:
>>  		The name of devfreq object denoted as ... is same as the
>>  		name of device using devfreq.
>>  
>> +What:		/sys/class/devfreq/.../name
>> +Date:		November 2019
>> +Contact:	Chanwoo Choi <cw00.choi@samsung.com>
>> +Description:
>> +		The /sys/class/devfreq/.../name shows the name of device
>> +		of the corresponding devfreq object.
>> +
>>  What:		/sys/class/devfreq/.../governor
>>  Date:		September 2011
>>  Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 65a4b6cf3fa5..6f4d93d2a651 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -1169,6 +1169,14 @@ int devfreq_remove_governor(struct devfreq_governor *governor)
>>  }
>>  EXPORT_SYMBOL(devfreq_remove_governor);
>>  
>> +static ssize_t name_show(struct device *dev,
>> +			struct device_attribute *attr, char *buf)
>> +{
>> +	struct devfreq *devfreq = to_devfreq(dev);
>> +	return sprintf(buf, "%s\n", dev_name(devfreq->dev.parent));
> 
> Why is the parent's name being set here, and not the device name?

The device name style in struct devfreq is 'devfreq%d' instead of
parent device name in order to keep the consistent naming style for devfreq device
as I mentioned above. 'devfreq%d' name is consistent name style for devfreq device.
But, it don't show the real h/w device name. So, show the parent device name
which is specified on device-tree file.

> 
> The device name should be the name of the directory, and the parent's
> name is the name of the parent directory, why is a sysfs attribute for a
> name needed at all?

I add my comment why 'name' attribute is needed with the example of
other subsystem in the linux kernel. Instead of adding duplicate answer,
you could check my comment above.

> 
> confused,
> 
> greg k-h
> 
> 

Best Regards,
Chanwoo Choi

Re: [PATCH v3] PM / devfreq: Add new name attribute for sysfs

[Greg KH]

On Tue, Nov 26, 2019 at 12:08:18PM +0900, Chanwoo Choi wrote:
> Hi Greg,
> 
> On 11/25/19 5:50 PM, Greg KH wrote:
> > On Mon, Nov 25, 2019 at 10:03:57AM +0900, Chanwoo Choi wrote:
> >> The 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.
> >>
> >> Cc: stable@vger.kernel.org
> >> Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
> >> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
> >> ---
> >>  Changes from v2:
> >> - Change the order of name_show() according to the sequence in devfreq_attrs[]
> >>
> >> Changes from v1:
> >> - Update sysfs-class-devfreq documentation
> >> - Show device name directly from 'devfreq->dev.parent'
> >>
> > 
> > Shouldn't you just revert the original patch here?  Why did the sysfs
> > file change?
> 
> The initial devfreq code used the parent device name for device name
> corresponding to devfreq object instead of 'devfreq%d' style.
> Before applied The commit 4585fbcb5331 ("PM / devfreq: Modify
> the device name as devfreq(X) for sysfs"), the devfreq sysfs
> showed the parent device name as following:
> 
> For example on Odroid-XU3 board before applied the commit 4585fbcb5331,
> 	/sys/class/devfreq/soc:bus_wcore
> 	/sys/class/devfreq/soc:bus_noc
> 	...(skip)
> 
> 
> But, I think that devfreq subsystem had to show the consistent
> sysfs entry name for devfreq device like input, thermal, hwmon subsystem.
> 
> For example on Odroid-XU3 board,
> - The input subsystem show the 'input%d' style for input device.
> $root@localhost:/# ls /sys/class/input/                                         
> event0  event1  input0  input1  mice  mouse0
> 
> - The thermal subsystem show the 'cooling_device%d' style for thermal cooling device.
> $ root@localhost:/# ls /sys/class/thermal/                                       
> cooling_device0  cooling_device2  thermal_zone1  thermal_zone3
> cooling_device1  thermal_zone0    thermal_zone2  thermal_zone4
> 
> - The hwmon subsystem show the 'hwmon%d' style for h/w monitor device.
> $root@localhost:/# ls /sys/class/hwmon/                                         
> hwmon0
> 
> 
> So, I tried to make the consistent sysfs entry name for devfreq device
> by contributing commit 4585fbcb5331 ("PM / devfreq: Modify the device name as
> devfreq(X) for sysfs"). But, The commit 4585fbcb5331 have missed that sysfs
> interface had to provide the real device name. Some subsystem like thermal
> and hwmon provide the device type or device name through sysfs interface.
> It is possible to make the user to find their own specific device by iteration
> on user-space.
> 
> root@localhost:/# cat /sys/class/thermal/cooling_device0/type 
> pwm-fan
> root@localhost:/# cat /sys/class/thermal/cooling_device1/type                  
> thermal-cpufreq-0
> root@localhost:/# cat /sys/class/thermal/cooling_device2/type                  
> thermal-cpufreq-1
> 
> root@localhost:/# cat /sys/class/hwmon/hwmon0/name                             
> pwmfan
> 
> 
> So, I add the new 'name' attribute of sysfs for devfreq device.
> 
> > 
> >> Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
> >>  drivers/devfreq/devfreq.c                     | 9 +++++++++
> >>  2 files changed, 16 insertions(+)
> >>
> >> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
> >> index 01196e19afca..75897e2fde43 100644
> >> --- a/Documentation/ABI/testing/sysfs-class-devfreq
> >> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
> >> @@ -7,6 +7,13 @@ Description:
> >>  		The name of devfreq object denoted as ... is same as the
> >>  		name of device using devfreq.
> >>  
> >> +What:		/sys/class/devfreq/.../name
> >> +Date:		November 2019
> >> +Contact:	Chanwoo Choi <cw00.choi@samsung.com>
> >> +Description:
> >> +		The /sys/class/devfreq/.../name shows the name of device
> >> +		of the corresponding devfreq object.
> >> +
> >>  What:		/sys/class/devfreq/.../governor
> >>  Date:		September 2011
> >>  Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
> >> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> >> index 65a4b6cf3fa5..6f4d93d2a651 100644
> >> --- a/drivers/devfreq/devfreq.c
> >> +++ b/drivers/devfreq/devfreq.c
> >> @@ -1169,6 +1169,14 @@ int devfreq_remove_governor(struct devfreq_governor *governor)
> >>  }
> >>  EXPORT_SYMBOL(devfreq_remove_governor);
> >>  
> >> +static ssize_t name_show(struct device *dev,
> >> +			struct device_attribute *attr, char *buf)
> >> +{
> >> +	struct devfreq *devfreq = to_devfreq(dev);
> >> +	return sprintf(buf, "%s\n", dev_name(devfreq->dev.parent));
> > 
> > Why is the parent's name being set here, and not the device name?
> 
> The device name style in struct devfreq is 'devfreq%d' instead of
> parent device name in order to keep the consistent naming style for devfreq device
> as I mentioned above. 'devfreq%d' name is consistent name style for devfreq device.
> But, it don't show the real h/w device name. So, show the parent device name
> which is specified on device-tree file.

I'm sorry, but I still do not understand.  Can you show me the directory
tree before and after here?

thanks,

greg k-h

Re: [PATCH v3] PM / devfreq: Add new name attribute for sysfs

[Chanwoo Choi]

On 11/26/19 4:53 PM, Greg KH wrote:
> On Tue, Nov 26, 2019 at 12:08:18PM +0900, Chanwoo Choi wrote:
>> Hi Greg,
>>
>> On 11/25/19 5:50 PM, Greg KH wrote:
>>> On Mon, Nov 25, 2019 at 10:03:57AM +0900, Chanwoo Choi wrote:
>>>> The 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.
>>>>
>>>> Cc: stable@vger.kernel.org
>>>> Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
>>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>>> ---
>>>>  Changes from v2:
>>>> - Change the order of name_show() according to the sequence in devfreq_attrs[]
>>>>
>>>> Changes from v1:
>>>> - Update sysfs-class-devfreq documentation
>>>> - Show device name directly from 'devfreq->dev.parent'
>>>>
>>>
>>> Shouldn't you just revert the original patch here?  Why did the sysfs
>>> file change?
>>
>> The initial devfreq code used the parent device name for device name
>> corresponding to devfreq object instead of 'devfreq%d' style.
>> Before applied The commit 4585fbcb5331 ("PM / devfreq: Modify
>> the device name as devfreq(X) for sysfs"), the devfreq sysfs
>> showed the parent device name as following:
>>
>> For example on Odroid-XU3 board before applied the commit 4585fbcb5331,
>> 	/sys/class/devfreq/soc:bus_wcore
>> 	/sys/class/devfreq/soc:bus_noc
>> 	...(skip)
>>
>>
>> But, I think that devfreq subsystem had to show the consistent
>> sysfs entry name for devfreq device like input, thermal, hwmon subsystem.
>>
>> For example on Odroid-XU3 board,
>> - The input subsystem show the 'input%d' style for input device.
>> $root@localhost:/# ls /sys/class/input/                                         
>> event0  event1  input0  input1  mice  mouse0
>>
>> - The thermal subsystem show the 'cooling_device%d' style for thermal cooling device.
>> $ root@localhost:/# ls /sys/class/thermal/                                       
>> cooling_device0  cooling_device2  thermal_zone1  thermal_zone3
>> cooling_device1  thermal_zone0    thermal_zone2  thermal_zone4
>>
>> - The hwmon subsystem show the 'hwmon%d' style for h/w monitor device.
>> $root@localhost:/# ls /sys/class/hwmon/                                         
>> hwmon0
>>
>>
>> So, I tried to make the consistent sysfs entry name for devfreq device
>> by contributing commit 4585fbcb5331 ("PM / devfreq: Modify the device name as
>> devfreq(X) for sysfs"). But, The commit 4585fbcb5331 have missed that sysfs
>> interface had to provide the real device name. Some subsystem like thermal
>> and hwmon provide the device type or device name through sysfs interface.
>> It is possible to make the user to find their own specific device by iteration
>> on user-space.
>>
>> root@localhost:/# cat /sys/class/thermal/cooling_device0/type 
>> pwm-fan
>> root@localhost:/# cat /sys/class/thermal/cooling_device1/type                  
>> thermal-cpufreq-0
>> root@localhost:/# cat /sys/class/thermal/cooling_device2/type                  
>> thermal-cpufreq-1
>>
>> root@localhost:/# cat /sys/class/hwmon/hwmon0/name                             
>> pwmfan
>>
>>
>> So, I add the new 'name' attribute of sysfs for devfreq device.
>>
>>>
>>>> Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
>>>>  drivers/devfreq/devfreq.c                     | 9 +++++++++
>>>>  2 files changed, 16 insertions(+)
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
>>>> index 01196e19afca..75897e2fde43 100644
>>>> --- a/Documentation/ABI/testing/sysfs-class-devfreq
>>>> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
>>>> @@ -7,6 +7,13 @@ Description:
>>>>  		The name of devfreq object denoted as ... is same as the
>>>>  		name of device using devfreq.
>>>>  
>>>> +What:		/sys/class/devfreq/.../name
>>>> +Date:		November 2019
>>>> +Contact:	Chanwoo Choi <cw00.choi@samsung.com>
>>>> +Description:
>>>> +		The /sys/class/devfreq/.../name shows the name of device
>>>> +		of the corresponding devfreq object.
>>>> +
>>>>  What:		/sys/class/devfreq/.../governor
>>>>  Date:		September 2011
>>>>  Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
>>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>>> index 65a4b6cf3fa5..6f4d93d2a651 100644
>>>> --- a/drivers/devfreq/devfreq.c
>>>> +++ b/drivers/devfreq/devfreq.c
>>>> @@ -1169,6 +1169,14 @@ int devfreq_remove_governor(struct devfreq_governor *governor)
>>>>  }
>>>>  EXPORT_SYMBOL(devfreq_remove_governor);
>>>>  
>>>> +static ssize_t name_show(struct device *dev,
>>>> +			struct device_attribute *attr, char *buf)
>>>> +{
>>>> +	struct devfreq *devfreq = to_devfreq(dev);
>>>> +	return sprintf(buf, "%s\n", dev_name(devfreq->dev.parent));
>>>
>>> Why is the parent's name being set here, and not the device name?
>>
>> The device name style in struct devfreq is 'devfreq%d' instead of
>> parent device name in order to keep the consistent naming style for devfreq device
>> as I mentioned above. 'devfreq%d' name is consistent name style for devfreq device.
>> But, it don't show the real h/w device name. So, show the parent device name
>> which is specified on device-tree file.
> 
> I'm sorry, but I still do not understand.  Can you show me the directory
> tree before and after here?
> 

I'm sorry for not enough description. I add the following example on Odroid-XU3 board.


1. Before applied commit 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X),

root@localhost:~# ls /sys/class/devfreq                                        
soc:bus_disp1       soc:bus_fsys_apb  soc:bus_gscl_scaler  soc:bus_mscl
soc:bus_disp1_fimd  soc:bus_g2d       soc:bus_jpeg         soc:bus_noc
soc:bus_fsys        soc:bus_g2d_acp   soc:bus_jpeg_apb     soc:bus_peri
soc:bus_fsys2       soc:bus_gen       soc:bus_mfc          soc:bus_wcore

root@localhost:~# ls -al /sys/class/devfreq
total 0
drwxr-xr-x  2 root root 0 Jan  1 09:00 .
drwxr-xr-x 52 root root 0 Jan  1 09:00 ..
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_disp1 -> ../../devices/platform/soc/soc:bus_disp1/devfreq/soc:bus_disp1
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_disp1_fimd -> ../../devices/platform/soc/soc:bus_disp1_fimd/devfreq/soc:bus_did
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys -> ../../devices/platform/soc/soc:bus_fsys/devfreq/soc:bus_fsys
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys2 -> ../../devices/platform/soc/soc:bus_fsys2/devfreq/soc:bus_fsys2
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys_apb -> ../../devices/platform/soc/soc:bus_fsys_apb/devfreq/soc:bus_fsys_ab
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_g2d -> ../../devices/platform/soc/soc:bus_g2d/devfreq/soc:bus_g2d
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_g2d_acp -> ../../devices/platform/soc/soc:bus_g2d_acp/devfreq/soc:bus_g2d_acp
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_gen -> ../../devices/platform/soc/soc:bus_gen/devfreq/soc:bus_gen
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_gscl_scaler -> ../../devices/platform/soc/soc:bus_gscl_scaler/devfreq/soc:bus_r
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_jpeg -> ../../devices/platform/soc/soc:bus_jpeg/devfreq/soc:bus_jpeg
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_jpeg_apb -> ../../devices/platform/soc/soc:bus_jpeg_apb/devfreq/soc:bus_jpeg_ab
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_mfc -> ../../devices/platform/soc/soc:bus_mfc/devfreq/soc:bus_mfc
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_mscl -> ../../devices/platform/soc/soc:bus_mscl/devfreq/soc:bus_mscl
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_noc -> ../../devices/platform/soc/soc:bus_noc/devfreq/soc:bus_noc
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_peri -> ../../devices/platform/soc/soc:bus_peri/devfreq/soc:bus_peri
lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_wcore -> ../../devices/platform/soc/soc:bus_wcore/devfreq/soc:bus_wcore



2. After applied commit 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X),

root@localhost:~# ls  /sys/class/devfreq                                       
devfreq0   devfreq11  devfreq14  devfreq3  devfreq6  devfreq9
devfreq1   devfreq12  devfreq15  devfreq4  devfreq7
devfreq10  devfreq13  devfreq2   devfreq5  devfreq8

root@localhost:~# ls -al /sys/class/devfreq                                    
total 0
drwxr-xr-x  2 root root 0 Jan  1 09:02 .
drwxr-xr-x 52 root root 0 Jan  1 09:02 ..
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq0 -> ../../devices/platform/soc/soc:bus_wcore/devfreq/devfreq0
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq1 -> ../../devices/platform/soc/soc:bus_noc/devfreq/devfreq1
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq10 -> ../../devices/platform/soc/soc:bus_jpeg/devfreq/devfreq10
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq11 -> ../../devices/platform/soc/soc:bus_jpeg_apb/devfreq/devfreq11
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq12 -> ../../devices/platform/soc/soc:bus_disp1_fimd/devfreq/devfreq12
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq13 -> ../../devices/platform/soc/soc:bus_disp1/devfreq/devfreq13
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq14 -> ../../devices/platform/soc/soc:bus_gscl_scaler/devfreq/devfreq14
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq15 -> ../../devices/platform/soc/soc:bus_mscl/devfreq/devfreq15
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq2 -> ../../devices/platform/soc/soc:bus_fsys_apb/devfreq/devfreq2
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq3 -> ../../devices/platform/soc/soc:bus_fsys/devfreq/devfreq3
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq4 -> ../../devices/platform/soc/soc:bus_fsys2/devfreq/devfreq4
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq5 -> ../../devices/platform/soc/soc:bus_mfc/devfreq/devfreq5
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq6 -> ../../devices/platform/soc/soc:bus_gen/devfreq/devfreq6
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq7 -> ../../devices/platform/soc/soc:bus_peri/devfreq/devfreq7
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq8 -> ../../devices/platform/soc/soc:bus_g2d/devfreq/devfreq8
lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq9 -> ../../devices/platform/soc/soc:bus_g2d_acp/devfreq/devfreq9


Best Regards,
Chanwoo Choi

Re: [PATCH v3] PM / devfreq: Add new name attribute for sysfs

[Greg KH]

On Tue, Nov 26, 2019 at 05:35:28PM +0900, Chanwoo Choi wrote:
> On 11/26/19 4:53 PM, Greg KH wrote:
> > On Tue, Nov 26, 2019 at 12:08:18PM +0900, Chanwoo Choi wrote:
> >> Hi Greg,
> >>
> >> On 11/25/19 5:50 PM, Greg KH wrote:
> >>> On Mon, Nov 25, 2019 at 10:03:57AM +0900, Chanwoo Choi wrote:
> >>>> The 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.
> >>>>
> >>>> Cc: stable@vger.kernel.org
> >>>> Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
> >>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
> >>>> ---
> >>>>  Changes from v2:
> >>>> - Change the order of name_show() according to the sequence in devfreq_attrs[]
> >>>>
> >>>> Changes from v1:
> >>>> - Update sysfs-class-devfreq documentation
> >>>> - Show device name directly from 'devfreq->dev.parent'
> >>>>
> >>>
> >>> Shouldn't you just revert the original patch here?  Why did the sysfs
> >>> file change?
> >>
> >> The initial devfreq code used the parent device name for device name
> >> corresponding to devfreq object instead of 'devfreq%d' style.
> >> Before applied The commit 4585fbcb5331 ("PM / devfreq: Modify
> >> the device name as devfreq(X) for sysfs"), the devfreq sysfs
> >> showed the parent device name as following:
> >>
> >> For example on Odroid-XU3 board before applied the commit 4585fbcb5331,
> >> 	/sys/class/devfreq/soc:bus_wcore
> >> 	/sys/class/devfreq/soc:bus_noc
> >> 	...(skip)
> >>
> >>
> >> But, I think that devfreq subsystem had to show the consistent
> >> sysfs entry name for devfreq device like input, thermal, hwmon subsystem.
> >>
> >> For example on Odroid-XU3 board,
> >> - The input subsystem show the 'input%d' style for input device.
> >> $root@localhost:/# ls /sys/class/input/                                         
> >> event0  event1  input0  input1  mice  mouse0
> >>
> >> - The thermal subsystem show the 'cooling_device%d' style for thermal cooling device.
> >> $ root@localhost:/# ls /sys/class/thermal/                                       
> >> cooling_device0  cooling_device2  thermal_zone1  thermal_zone3
> >> cooling_device1  thermal_zone0    thermal_zone2  thermal_zone4
> >>
> >> - The hwmon subsystem show the 'hwmon%d' style for h/w monitor device.
> >> $root@localhost:/# ls /sys/class/hwmon/                                         
> >> hwmon0
> >>
> >>
> >> So, I tried to make the consistent sysfs entry name for devfreq device
> >> by contributing commit 4585fbcb5331 ("PM / devfreq: Modify the device name as
> >> devfreq(X) for sysfs"). But, The commit 4585fbcb5331 have missed that sysfs
> >> interface had to provide the real device name. Some subsystem like thermal
> >> and hwmon provide the device type or device name through sysfs interface.
> >> It is possible to make the user to find their own specific device by iteration
> >> on user-space.
> >>
> >> root@localhost:/# cat /sys/class/thermal/cooling_device0/type 
> >> pwm-fan
> >> root@localhost:/# cat /sys/class/thermal/cooling_device1/type                  
> >> thermal-cpufreq-0
> >> root@localhost:/# cat /sys/class/thermal/cooling_device2/type                  
> >> thermal-cpufreq-1
> >>
> >> root@localhost:/# cat /sys/class/hwmon/hwmon0/name                             
> >> pwmfan
> >>
> >>
> >> So, I add the new 'name' attribute of sysfs for devfreq device.
> >>
> >>>
> >>>> Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
> >>>>  drivers/devfreq/devfreq.c                     | 9 +++++++++
> >>>>  2 files changed, 16 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
> >>>> index 01196e19afca..75897e2fde43 100644
> >>>> --- a/Documentation/ABI/testing/sysfs-class-devfreq
> >>>> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
> >>>> @@ -7,6 +7,13 @@ Description:
> >>>>  		The name of devfreq object denoted as ... is same as the
> >>>>  		name of device using devfreq.
> >>>>  
> >>>> +What:		/sys/class/devfreq/.../name
> >>>> +Date:		November 2019
> >>>> +Contact:	Chanwoo Choi <cw00.choi@samsung.com>
> >>>> +Description:
> >>>> +		The /sys/class/devfreq/.../name shows the name of device
> >>>> +		of the corresponding devfreq object.
> >>>> +
> >>>>  What:		/sys/class/devfreq/.../governor
> >>>>  Date:		September 2011
> >>>>  Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
> >>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> >>>> index 65a4b6cf3fa5..6f4d93d2a651 100644
> >>>> --- a/drivers/devfreq/devfreq.c
> >>>> +++ b/drivers/devfreq/devfreq.c
> >>>> @@ -1169,6 +1169,14 @@ int devfreq_remove_governor(struct devfreq_governor *governor)
> >>>>  }
> >>>>  EXPORT_SYMBOL(devfreq_remove_governor);
> >>>>  
> >>>> +static ssize_t name_show(struct device *dev,
> >>>> +			struct device_attribute *attr, char *buf)
> >>>> +{
> >>>> +	struct devfreq *devfreq = to_devfreq(dev);
> >>>> +	return sprintf(buf, "%s\n", dev_name(devfreq->dev.parent));
> >>>
> >>> Why is the parent's name being set here, and not the device name?
> >>
> >> The device name style in struct devfreq is 'devfreq%d' instead of
> >> parent device name in order to keep the consistent naming style for devfreq device
> >> as I mentioned above. 'devfreq%d' name is consistent name style for devfreq device.
> >> But, it don't show the real h/w device name. So, show the parent device name
> >> which is specified on device-tree file.
> > 
> > I'm sorry, but I still do not understand.  Can you show me the directory
> > tree before and after here?
> > 
> 
> I'm sorry for not enough description. I add the following example on Odroid-XU3 board.
> 
> 
> 1. Before applied commit 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X),
> 
> root@localhost:~# ls /sys/class/devfreq                                        
> soc:bus_disp1       soc:bus_fsys_apb  soc:bus_gscl_scaler  soc:bus_mscl
> soc:bus_disp1_fimd  soc:bus_g2d       soc:bus_jpeg         soc:bus_noc
> soc:bus_fsys        soc:bus_g2d_acp   soc:bus_jpeg_apb     soc:bus_peri
> soc:bus_fsys2       soc:bus_gen       soc:bus_mfc          soc:bus_wcore
> 
> root@localhost:~# ls -al /sys/class/devfreq
> total 0
> drwxr-xr-x  2 root root 0 Jan  1 09:00 .
> drwxr-xr-x 52 root root 0 Jan  1 09:00 ..
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_disp1 -> ../../devices/platform/soc/soc:bus_disp1/devfreq/soc:bus_disp1

Ah, that's odd, ok.

> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_disp1_fimd -> ../../devices/platform/soc/soc:bus_disp1_fimd/devfreq/soc:bus_did
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys -> ../../devices/platform/soc/soc:bus_fsys/devfreq/soc:bus_fsys
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys2 -> ../../devices/platform/soc/soc:bus_fsys2/devfreq/soc:bus_fsys2
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys_apb -> ../../devices/platform/soc/soc:bus_fsys_apb/devfreq/soc:bus_fsys_ab
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_g2d -> ../../devices/platform/soc/soc:bus_g2d/devfreq/soc:bus_g2d
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_g2d_acp -> ../../devices/platform/soc/soc:bus_g2d_acp/devfreq/soc:bus_g2d_acp
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_gen -> ../../devices/platform/soc/soc:bus_gen/devfreq/soc:bus_gen
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_gscl_scaler -> ../../devices/platform/soc/soc:bus_gscl_scaler/devfreq/soc:bus_r
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_jpeg -> ../../devices/platform/soc/soc:bus_jpeg/devfreq/soc:bus_jpeg
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_jpeg_apb -> ../../devices/platform/soc/soc:bus_jpeg_apb/devfreq/soc:bus_jpeg_ab
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_mfc -> ../../devices/platform/soc/soc:bus_mfc/devfreq/soc:bus_mfc
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_mscl -> ../../devices/platform/soc/soc:bus_mscl/devfreq/soc:bus_mscl
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_noc -> ../../devices/platform/soc/soc:bus_noc/devfreq/soc:bus_noc
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_peri -> ../../devices/platform/soc/soc:bus_peri/devfreq/soc:bus_peri
> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_wcore -> ../../devices/platform/soc/soc:bus_wcore/devfreq/soc:bus_wcore
> 
> 
> 
> 2. After applied commit 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X),
> 
> root@localhost:~# ls  /sys/class/devfreq                                       
> devfreq0   devfreq11  devfreq14  devfreq3  devfreq6  devfreq9
> devfreq1   devfreq12  devfreq15  devfreq4  devfreq7
> devfreq10  devfreq13  devfreq2   devfreq5  devfreq8

That's better.

> 
> root@localhost:~# ls -al /sys/class/devfreq                                    
> total 0
> drwxr-xr-x  2 root root 0 Jan  1 09:02 .
> drwxr-xr-x 52 root root 0 Jan  1 09:02 ..
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq0 -> ../../devices/platform/soc/soc:bus_wcore/devfreq/devfreq0
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq1 -> ../../devices/platform/soc/soc:bus_noc/devfreq/devfreq1
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq10 -> ../../devices/platform/soc/soc:bus_jpeg/devfreq/devfreq10
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq11 -> ../../devices/platform/soc/soc:bus_jpeg_apb/devfreq/devfreq11
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq12 -> ../../devices/platform/soc/soc:bus_disp1_fimd/devfreq/devfreq12
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq13 -> ../../devices/platform/soc/soc:bus_disp1/devfreq/devfreq13
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq14 -> ../../devices/platform/soc/soc:bus_gscl_scaler/devfreq/devfreq14
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq15 -> ../../devices/platform/soc/soc:bus_mscl/devfreq/devfreq15
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq2 -> ../../devices/platform/soc/soc:bus_fsys_apb/devfreq/devfreq2
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq3 -> ../../devices/platform/soc/soc:bus_fsys/devfreq/devfreq3
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq4 -> ../../devices/platform/soc/soc:bus_fsys2/devfreq/devfreq4
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq5 -> ../../devices/platform/soc/soc:bus_mfc/devfreq/devfreq5
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq6 -> ../../devices/platform/soc/soc:bus_gen/devfreq/devfreq6
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq7 -> ../../devices/platform/soc/soc:bus_peri/devfreq/devfreq7
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq8 -> ../../devices/platform/soc/soc:bus_g2d/devfreq/devfreq8
> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq9 -> ../../devices/platform/soc/soc:bus_g2d_acp/devfreq/devfreq9

Ok, this looks a bit better, but why is there the extra "devfreq"
directory in there?  That was in the original as well, but that feels
odd.

thanks,

greg k-h

Re: [PATCH v3] PM / devfreq: Add new name attribute for sysfs

[Chanwoo Choi]

On 11/26/19 6:15 PM, Greg KH wrote:
> On Tue, Nov 26, 2019 at 05:35:28PM +0900, Chanwoo Choi wrote:
>> On 11/26/19 4:53 PM, Greg KH wrote:
>>> On Tue, Nov 26, 2019 at 12:08:18PM +0900, Chanwoo Choi wrote:
>>>> Hi Greg,
>>>>
>>>> On 11/25/19 5:50 PM, Greg KH wrote:
>>>>> On Mon, Nov 25, 2019 at 10:03:57AM +0900, Chanwoo Choi wrote:
>>>>>> The 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.
>>>>>>
>>>>>> Cc: stable@vger.kernel.org
>>>>>> Fixes: 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X) for sysfs")
>>>>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>>>>> ---
>>>>>>  Changes from v2:
>>>>>> - Change the order of name_show() according to the sequence in devfreq_attrs[]
>>>>>>
>>>>>> Changes from v1:
>>>>>> - Update sysfs-class-devfreq documentation
>>>>>> - Show device name directly from 'devfreq->dev.parent'
>>>>>>
>>>>>
>>>>> Shouldn't you just revert the original patch here?  Why did the sysfs
>>>>> file change?
>>>>
>>>> The initial devfreq code used the parent device name for device name
>>>> corresponding to devfreq object instead of 'devfreq%d' style.
>>>> Before applied The commit 4585fbcb5331 ("PM / devfreq: Modify
>>>> the device name as devfreq(X) for sysfs"), the devfreq sysfs
>>>> showed the parent device name as following:
>>>>
>>>> For example on Odroid-XU3 board before applied the commit 4585fbcb5331,
>>>> 	/sys/class/devfreq/soc:bus_wcore
>>>> 	/sys/class/devfreq/soc:bus_noc
>>>> 	...(skip)
>>>>
>>>>
>>>> But, I think that devfreq subsystem had to show the consistent
>>>> sysfs entry name for devfreq device like input, thermal, hwmon subsystem.
>>>>
>>>> For example on Odroid-XU3 board,
>>>> - The input subsystem show the 'input%d' style for input device.
>>>> $root@localhost:/# ls /sys/class/input/                                         
>>>> event0  event1  input0  input1  mice  mouse0
>>>>
>>>> - The thermal subsystem show the 'cooling_device%d' style for thermal cooling device.
>>>> $ root@localhost:/# ls /sys/class/thermal/                                       
>>>> cooling_device0  cooling_device2  thermal_zone1  thermal_zone3
>>>> cooling_device1  thermal_zone0    thermal_zone2  thermal_zone4
>>>>
>>>> - The hwmon subsystem show the 'hwmon%d' style for h/w monitor device.
>>>> $root@localhost:/# ls /sys/class/hwmon/                                         
>>>> hwmon0
>>>>
>>>>
>>>> So, I tried to make the consistent sysfs entry name for devfreq device
>>>> by contributing commit 4585fbcb5331 ("PM / devfreq: Modify the device name as
>>>> devfreq(X) for sysfs"). But, The commit 4585fbcb5331 have missed that sysfs
>>>> interface had to provide the real device name. Some subsystem like thermal
>>>> and hwmon provide the device type or device name through sysfs interface.
>>>> It is possible to make the user to find their own specific device by iteration
>>>> on user-space.
>>>>
>>>> root@localhost:/# cat /sys/class/thermal/cooling_device0/type 
>>>> pwm-fan
>>>> root@localhost:/# cat /sys/class/thermal/cooling_device1/type                  
>>>> thermal-cpufreq-0
>>>> root@localhost:/# cat /sys/class/thermal/cooling_device2/type                  
>>>> thermal-cpufreq-1
>>>>
>>>> root@localhost:/# cat /sys/class/hwmon/hwmon0/name                             
>>>> pwmfan
>>>>
>>>>
>>>> So, I add the new 'name' attribute of sysfs for devfreq device.
>>>>
>>>>>
>>>>>> Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
>>>>>>  drivers/devfreq/devfreq.c                     | 9 +++++++++
>>>>>>  2 files changed, 16 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
>>>>>> index 01196e19afca..75897e2fde43 100644
>>>>>> --- a/Documentation/ABI/testing/sysfs-class-devfreq
>>>>>> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
>>>>>> @@ -7,6 +7,13 @@ Description:
>>>>>>  		The name of devfreq object denoted as ... is same as the
>>>>>>  		name of device using devfreq.
>>>>>>  
>>>>>> +What:		/sys/class/devfreq/.../name
>>>>>> +Date:		November 2019
>>>>>> +Contact:	Chanwoo Choi <cw00.choi@samsung.com>
>>>>>> +Description:
>>>>>> +		The /sys/class/devfreq/.../name shows the name of device
>>>>>> +		of the corresponding devfreq object.
>>>>>> +
>>>>>>  What:		/sys/class/devfreq/.../governor
>>>>>>  Date:		September 2011
>>>>>>  Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
>>>>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>>>>> index 65a4b6cf3fa5..6f4d93d2a651 100644
>>>>>> --- a/drivers/devfreq/devfreq.c
>>>>>> +++ b/drivers/devfreq/devfreq.c
>>>>>> @@ -1169,6 +1169,14 @@ int devfreq_remove_governor(struct devfreq_governor *governor)
>>>>>>  }
>>>>>>  EXPORT_SYMBOL(devfreq_remove_governor);
>>>>>>  
>>>>>> +static ssize_t name_show(struct device *dev,
>>>>>> +			struct device_attribute *attr, char *buf)
>>>>>> +{
>>>>>> +	struct devfreq *devfreq = to_devfreq(dev);
>>>>>> +	return sprintf(buf, "%s\n", dev_name(devfreq->dev.parent));
>>>>>
>>>>> Why is the parent's name being set here, and not the device name?
>>>>
>>>> The device name style in struct devfreq is 'devfreq%d' instead of
>>>> parent device name in order to keep the consistent naming style for devfreq device
>>>> as I mentioned above. 'devfreq%d' name is consistent name style for devfreq device.
>>>> But, it don't show the real h/w device name. So, show the parent device name
>>>> which is specified on device-tree file.
>>>
>>> I'm sorry, but I still do not understand.  Can you show me the directory
>>> tree before and after here?
>>>
>>
>> I'm sorry for not enough description. I add the following example on Odroid-XU3 board.
>>
>>
>> 1. Before applied commit 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X),
>>
>> root@localhost:~# ls /sys/class/devfreq                                        
>> soc:bus_disp1       soc:bus_fsys_apb  soc:bus_gscl_scaler  soc:bus_mscl
>> soc:bus_disp1_fimd  soc:bus_g2d       soc:bus_jpeg         soc:bus_noc
>> soc:bus_fsys        soc:bus_g2d_acp   soc:bus_jpeg_apb     soc:bus_peri
>> soc:bus_fsys2       soc:bus_gen       soc:bus_mfc          soc:bus_wcore
>>
>> root@localhost:~# ls -al /sys/class/devfreq
>> total 0
>> drwxr-xr-x  2 root root 0 Jan  1 09:00 .
>> drwxr-xr-x 52 root root 0 Jan  1 09:00 ..
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_disp1 -> ../../devices/platform/soc/soc:bus_disp1/devfreq/soc:bus_disp1
> 
> Ah, that's odd, ok.
> 
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_disp1_fimd -> ../../devices/platform/soc/soc:bus_disp1_fimd/devfreq/soc:bus_did
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys -> ../../devices/platform/soc/soc:bus_fsys/devfreq/soc:bus_fsys
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys2 -> ../../devices/platform/soc/soc:bus_fsys2/devfreq/soc:bus_fsys2
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_fsys_apb -> ../../devices/platform/soc/soc:bus_fsys_apb/devfreq/soc:bus_fsys_ab
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_g2d -> ../../devices/platform/soc/soc:bus_g2d/devfreq/soc:bus_g2d
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_g2d_acp -> ../../devices/platform/soc/soc:bus_g2d_acp/devfreq/soc:bus_g2d_acp
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_gen -> ../../devices/platform/soc/soc:bus_gen/devfreq/soc:bus_gen
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_gscl_scaler -> ../../devices/platform/soc/soc:bus_gscl_scaler/devfreq/soc:bus_r
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_jpeg -> ../../devices/platform/soc/soc:bus_jpeg/devfreq/soc:bus_jpeg
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_jpeg_apb -> ../../devices/platform/soc/soc:bus_jpeg_apb/devfreq/soc:bus_jpeg_ab
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_mfc -> ../../devices/platform/soc/soc:bus_mfc/devfreq/soc:bus_mfc
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_mscl -> ../../devices/platform/soc/soc:bus_mscl/devfreq/soc:bus_mscl
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_noc -> ../../devices/platform/soc/soc:bus_noc/devfreq/soc:bus_noc
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_peri -> ../../devices/platform/soc/soc:bus_peri/devfreq/soc:bus_peri
>> lrwxrwxrwx  1 root root 0 Jan  1 09:00 soc:bus_wcore -> ../../devices/platform/soc/soc:bus_wcore/devfreq/soc:bus_wcore
>>
>>
>>
>> 2. After applied commit 4585fbcb5331 ("PM / devfreq: Modify the device name as devfreq(X),
>>
>> root@localhost:~# ls  /sys/class/devfreq                                       
>> devfreq0   devfreq11  devfreq14  devfreq3  devfreq6  devfreq9
>> devfreq1   devfreq12  devfreq15  devfreq4  devfreq7
>> devfreq10  devfreq13  devfreq2   devfreq5  devfreq8
> 
> That's better.
> 
>>
>> root@localhost:~# ls -al /sys/class/devfreq                                    
>> total 0
>> drwxr-xr-x  2 root root 0 Jan  1 09:02 .
>> drwxr-xr-x 52 root root 0 Jan  1 09:02 ..
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq0 -> ../../devices/platform/soc/soc:bus_wcore/devfreq/devfreq0
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq1 -> ../../devices/platform/soc/soc:bus_noc/devfreq/devfreq1
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq10 -> ../../devices/platform/soc/soc:bus_jpeg/devfreq/devfreq10
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq11 -> ../../devices/platform/soc/soc:bus_jpeg_apb/devfreq/devfreq11
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq12 -> ../../devices/platform/soc/soc:bus_disp1_fimd/devfreq/devfreq12
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq13 -> ../../devices/platform/soc/soc:bus_disp1/devfreq/devfreq13
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq14 -> ../../devices/platform/soc/soc:bus_gscl_scaler/devfreq/devfreq14
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq15 -> ../../devices/platform/soc/soc:bus_mscl/devfreq/devfreq15
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq2 -> ../../devices/platform/soc/soc:bus_fsys_apb/devfreq/devfreq2
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq3 -> ../../devices/platform/soc/soc:bus_fsys/devfreq/devfreq3
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq4 -> ../../devices/platform/soc/soc:bus_fsys2/devfreq/devfreq4
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq5 -> ../../devices/platform/soc/soc:bus_mfc/devfreq/devfreq5
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq6 -> ../../devices/platform/soc/soc:bus_gen/devfreq/devfreq6
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq7 -> ../../devices/platform/soc/soc:bus_peri/devfreq/devfreq7
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq8 -> ../../devices/platform/soc/soc:bus_g2d/devfreq/devfreq8
>> lrwxrwxrwx  1 root root 0 Jan  1 09:02 devfreq9 -> ../../devices/platform/soc/soc:bus_g2d_acp/devfreq/devfreq9
> 
> Ok, this looks a bit better, but why is there the extra "devfreq"
> directory in there?  That was in the original as well, but that feels
> odd.

What extra directory are you talking about? I didn't create
the any extra directory for devfreq.

If you mention the following 'devfreq' directory, 
it is created by basic device driver code in linux kernel.
- /sys/devices/platform/soc/soc\:bus_wcore/devfreq/

or

Each devfreq0~15 directories indicates the each devfreq device.


For example, show the info of each path
root@localhost:~# ls -al /sys/devices/platform/soc/soc\:bus_wcore/             
total 0
drwxr-xr-x   4 root root    0 Jan  1 09:56 .
drwxr-xr-x 109 root root    0 Jan  1 09:56 ..
drwxr-xr-x   3 root root    0 Jan  1 09:56 devfreq
lrwxrwxrwx   1 root root    0 Jan  1 09:57 driver -> ../../../../bus/platform/drivers/exynos-bus
-rw-r--r--   1 root root 4096 Jan  1 09:57 driver_override
-r--r--r--   1 root root 4096 Jan  1 09:57 modalias
lrwxrwxrwx   1 root root    0 Jan  1 09:57 of_node -> ../../../../firmware/devicetree/base/soc/bus_wcore
drwxr-xr-x   2 root root    0 Jan  1 09:57 power
lrwxrwxrwx   1 root root    0 Jan  1 09:56 subsystem -> ../../../../bus/platform
-rw-r--r--   1 root root 4096 Jan  1 09:56 uevent

root@localhost:~# ls -al /sys/devices/platform/soc/soc\:bus_wcore/devfreq/     
total 0
drwxr-xr-x 3 root root 0 Jan  1 09:56 .
drwxr-xr-x 4 root root 0 Jan  1 09:56 ..
drwxr-xr-x 3 root root 0 Jan  1 09:56 devfreq0

root@localhost:~# ls -al /sys/devices/platform/soc/soc\:bus_wcore/devfreq/devfreq0
drwxr-xr-x 3 root root    0 Jan  1 09:56 .
drwxr-xr-x 3 root root    0 Jan  1 09:56 ..
-r--r--r-- 1 root root 4096 Jan  1 10:03 available_frequencies
-r--r--r-- 1 root root 4096 Jan  1 10:03 available_governors
-r--r--r-- 1 root root 4096 Jan  1 10:03 cur_freq
lrwxrwxrwx 1 root root    0 Jan  1 10:03 device -> ../../../soc:bus_wcore
-rw-r--r-- 1 root root 4096 Jan  1 10:03 governor
-rw-r--r-- 1 root root 4096 Jan  1 10:03 max_freq
-rw-r--r-- 1 root root 4096 Jan  1 10:03 min_freq
-r--r--r-- 1 root root 4096 Jan  1 10:03 name
-rw-r--r-- 1 root root 4096 Jan  1 10:03 polling_interval
drwxr-xr-x 2 root root    0 Jan  1 10:03 power
lrwxrwxrwx 1 root root    0 Jan  1 09:56 subsystem -> ../../../../../../class/devfreq
-r--r--r-- 1 root root 4096 Jan  1 10:03 target_freq
-r--r--r-- 1 root root 4096 Jan  1 10:03 trans_stat
-rw-r--r-- 1 root root 4096 Jan  1 09:56 uevent




-- 
Best Regards,
Chanwoo Choi
Samsung Electronics