Ethtool question

Ethtool question

[Ben Greear]

I noticed today that setting some ethtool settings to the same value
returns an error code.  I would think this should silently return
success instead?  Makes it easier to call it from scripts this way:

[root@lf0313-6477 lanforge]# ethtool -L eth3 combined 1
combined unmodified, ignoring
no channel parameters changed, aborting
current values: tx 0 rx 0 other 1 combined 1
[root@lf0313-6477 lanforge]# echo $?
1

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Ethtool question

[John W. Linville]

On Wed, Oct 11, 2017 at 09:51:56AM -0700, Ben Greear wrote:
> I noticed today that setting some ethtool settings to the same value
> returns an error code.  I would think this should silently return
> success instead?  Makes it easier to call it from scripts this way:
> 
> [root@lf0313-6477 lanforge]# ethtool -L eth3 combined 1
> combined unmodified, ignoring
> no channel parameters changed, aborting
> current values: tx 0 rx 0 other 1 combined 1
> [root@lf0313-6477 lanforge]# echo $?
> 1

I just had this discussion a couple of months ago with someone. My
initial feeling was like you, a no-op is not a failure. But someone
convinced me otherwise...I will now endeavour to remember who that
was and how they convinced me...

Anyone else have input here?

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville@tuxdriver.com			might be all we have.  Be ready.

Re: Ethtool question

[David Miller]

From: "John W. Linville" <linville@tuxdriver.com>
Date: Wed, 11 Oct 2017 16:44:07 -0400

> On Wed, Oct 11, 2017 at 09:51:56AM -0700, Ben Greear wrote:
>> I noticed today that setting some ethtool settings to the same value
>> returns an error code.  I would think this should silently return
>> success instead?  Makes it easier to call it from scripts this way:
>> 
>> [root@lf0313-6477 lanforge]# ethtool -L eth3 combined 1
>> combined unmodified, ignoring
>> no channel parameters changed, aborting
>> current values: tx 0 rx 0 other 1 combined 1
>> [root@lf0313-6477 lanforge]# echo $?
>> 1
> 
> I just had this discussion a couple of months ago with someone. My
> initial feeling was like you, a no-op is not a failure. But someone
> convinced me otherwise...I will now endeavour to remember who that
> was and how they convinced me...
> 
> Anyone else have input here?

I guess this usually happens when drivers don't support changing the
settings at all.  So they just make their ethtool operation for the
'set' always return an error.

We could have a generic ethtool helper that does "get" and then if the
"set" request is identical just return zero.

But from another perspective, the error returned from the "set" in this
situation also indicates to the user that the driver does not support
the "set" operation which has value and meaning in and of itself.  And
we'd lose that with the given suggestion.

Re: Ethtool question

[Ben Greear]

On 10/11/2017 01:49 PM, David Miller wrote:
> From: "John W. Linville" <linville@tuxdriver.com>
> Date: Wed, 11 Oct 2017 16:44:07 -0400
>
>> On Wed, Oct 11, 2017 at 09:51:56AM -0700, Ben Greear wrote:
>>> I noticed today that setting some ethtool settings to the same value
>>> returns an error code.  I would think this should silently return
>>> success instead?  Makes it easier to call it from scripts this way:
>>>
>>> [root@lf0313-6477 lanforge]# ethtool -L eth3 combined 1
>>> combined unmodified, ignoring
>>> no channel parameters changed, aborting
>>> current values: tx 0 rx 0 other 1 combined 1
>>> [root@lf0313-6477 lanforge]# echo $?
>>> 1
>>
>> I just had this discussion a couple of months ago with someone. My
>> initial feeling was like you, a no-op is not a failure. But someone
>> convinced me otherwise...I will now endeavour to remember who that
>> was and how they convinced me...
>>
>> Anyone else have input here?
>
> I guess this usually happens when drivers don't support changing the
> settings at all.  So they just make their ethtool operation for the
> 'set' always return an error.
>
> We could have a generic ethtool helper that does "get" and then if the
> "set" request is identical just return zero.
>
> But from another perspective, the error returned from the "set" in this
> situation also indicates to the user that the driver does not support
> the "set" operation which has value and meaning in and of itself.  And
> we'd lose that with the given suggestion.

In my case, the driver (igb) does support the set, my program just made the same
ethtool call several times and it fails after the initial change (that actually
changes something), as best as I can figure.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Ethtool question

[Roopa Prabhu]

On Thu, Oct 12, 2017 at 2:45 PM, Ben Greear <greearb@candelatech.com> wrote:
> On 10/11/2017 01:49 PM, David Miller wrote:
>>
>> From: "John W. Linville" <linville@tuxdriver.com>
>> Date: Wed, 11 Oct 2017 16:44:07 -0400
>>
>>> On Wed, Oct 11, 2017 at 09:51:56AM -0700, Ben Greear wrote:
>>>>
>>>> I noticed today that setting some ethtool settings to the same value
>>>> returns an error code.  I would think this should silently return
>>>> success instead?  Makes it easier to call it from scripts this way:
>>>>
>>>> [root@lf0313-6477 lanforge]# ethtool -L eth3 combined 1
>>>> combined unmodified, ignoring
>>>> no channel parameters changed, aborting
>>>> current values: tx 0 rx 0 other 1 combined 1
>>>> [root@lf0313-6477 lanforge]# echo $?
>>>> 1
>>>
>>>
>>> I just had this discussion a couple of months ago with someone. My
>>> initial feeling was like you, a no-op is not a failure. But someone
>>> convinced me otherwise...I will now endeavour to remember who that
>>> was and how they convinced me...
>>>
>>> Anyone else have input here?
>>
>>
>> I guess this usually happens when drivers don't support changing the
>> settings at all.  So they just make their ethtool operation for the
>> 'set' always return an error.
>>
>> We could have a generic ethtool helper that does "get" and then if the
>> "set" request is identical just return zero.
>>
>> But from another perspective, the error returned from the "set" in this
>> situation also indicates to the user that the driver does not support
>> the "set" operation which has value and meaning in and of itself.  And
>> we'd lose that with the given suggestion.
>
>
> In my case, the driver (igb) does support the set, my program just made the
> same
> ethtool call several times and it fails after the initial change (that
> actually
> changes something), as best as I can figure.


This error is returned by ethtool user-space. It does a get, check and
then set if user has requested changes.

Re: Ethtool question

[Ben Greear]

On 10/12/2017 03:00 PM, Roopa Prabhu wrote:
> On Thu, Oct 12, 2017 at 2:45 PM, Ben Greear <greearb@candelatech.com> wrote:
>> On 10/11/2017 01:49 PM, David Miller wrote:
>>>
>>> From: "John W. Linville" <linville@tuxdriver.com>
>>> Date: Wed, 11 Oct 2017 16:44:07 -0400
>>>
>>>> On Wed, Oct 11, 2017 at 09:51:56AM -0700, Ben Greear wrote:
>>>>>
>>>>> I noticed today that setting some ethtool settings to the same value
>>>>> returns an error code.  I would think this should silently return
>>>>> success instead?  Makes it easier to call it from scripts this way:
>>>>>
>>>>> [root@lf0313-6477 lanforge]# ethtool -L eth3 combined 1
>>>>> combined unmodified, ignoring
>>>>> no channel parameters changed, aborting
>>>>> current values: tx 0 rx 0 other 1 combined 1
>>>>> [root@lf0313-6477 lanforge]# echo $?
>>>>> 1
>>>>
>>>>
>>>> I just had this discussion a couple of months ago with someone. My
>>>> initial feeling was like you, a no-op is not a failure. But someone
>>>> convinced me otherwise...I will now endeavour to remember who that
>>>> was and how they convinced me...
>>>>
>>>> Anyone else have input here?
>>>
>>>
>>> I guess this usually happens when drivers don't support changing the
>>> settings at all.  So they just make their ethtool operation for the
>>> 'set' always return an error.
>>>
>>> We could have a generic ethtool helper that does "get" and then if the
>>> "set" request is identical just return zero.
>>>
>>> But from another perspective, the error returned from the "set" in this
>>> situation also indicates to the user that the driver does not support
>>> the "set" operation which has value and meaning in and of itself.  And
>>> we'd lose that with the given suggestion.
>>
>>
>> In my case, the driver (igb) does support the set, my program just made the
>> same
>> ethtool call several times and it fails after the initial change (that
>> actually
>> changes something), as best as I can figure.
>
>
> This error is returned by ethtool user-space. It does a get, check and
> then set if user has requested changes.
>

So, should we fix ethtool to return 0 in this case instead of an error code?

I think so.  If the driver itself returns an error, then probably return the
error code and/or fix the driver as seems appropriate.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Ethtool question

[Gal Pressman]

On 16-Oct-17 21:10, Ben Greear wrote:
> On 10/12/2017 03:00 PM, Roopa Prabhu wrote:
>> On Thu, Oct 12, 2017 at 2:45 PM, Ben Greear <greearb@candelatech.com> wrote:
>>> On 10/11/2017 01:49 PM, David Miller wrote:
>>>>
>>>> From: "John W. Linville" <linville@tuxdriver.com>
>>>> Date: Wed, 11 Oct 2017 16:44:07 -0400
>>>>
>>>>> On Wed, Oct 11, 2017 at 09:51:56AM -0700, Ben Greear wrote:
>>>>>>
>>>>>> I noticed today that setting some ethtool settings to the same value
>>>>>> returns an error code.  I would think this should silently return
>>>>>> success instead?  Makes it easier to call it from scripts this way:
>>>>>>
>>>>>> [root@lf0313-6477 lanforge]# ethtool -L eth3 combined 1
>>>>>> combined unmodified, ignoring
>>>>>> no channel parameters changed, aborting
>>>>>> current values: tx 0 rx 0 other 1 combined 1
>>>>>> [root@lf0313-6477 lanforge]# echo $?
>>>>>> 1
>>>>>
>>>>>
>>>>> I just had this discussion a couple of months ago with someone. My
>>>>> initial feeling was like you, a no-op is not a failure. But someone
>>>>> convinced me otherwise...I will now endeavour to remember who that
>>>>> was and how they convinced me...
>>>>>
>>>>> Anyone else have input here?
>>>>
>>>>
>>>> I guess this usually happens when drivers don't support changing the
>>>> settings at all.  So they just make their ethtool operation for the
>>>> 'set' always return an error.
>>>>
>>>> We could have a generic ethtool helper that does "get" and then if the
>>>> "set" request is identical just return zero.
>>>>
>>>> But from another perspective, the error returned from the "set" in this
>>>> situation also indicates to the user that the driver does not support
>>>> the "set" operation which has value and meaning in and of itself.  And
>>>> we'd lose that with the given suggestion.
>>>
>>>
>>> In my case, the driver (igb) does support the set, my program just made the
>>> same
>>> ethtool call several times and it fails after the initial change (that
>>> actually
>>> changes something), as best as I can figure.
>>
>>
>> This error is returned by ethtool user-space. It does a get, check and
>> then set if user has requested changes.
>>
>
> So, should we fix ethtool to return 0 in this case instead of an error code?
>
> I think so.  If the driver itself returns an error, then probably return the
> error code and/or fix the driver as seems appropriate.
>
> Thanks,
> Ben
>

FWIW, seems like the code isn't consistent in this matter.
Setting pause/channels/coalescing with the same values will return an error code, but setting EEE will return success.