Re: [PATCH net-next V2 7/7] devlink: Add eswitch mode boot defaults

[Randy Dunlap <rdunlap@infradead.org>]

On 6/3/26 6:16 PM, Mark Bloch wrote:
> 
> 
> On 03/06/2026 23:06, Randy Dunlap wrote:
>> Hi.
>>
>> On 6/3/26 12:32 PM, Mark Bloch wrote:
>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>>> index 063c11ca33e5..7af9f2898d92 100644
>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>> @@ -1264,6 +1264,31 @@ Kernel parameters
>>>  	dell_smm_hwmon.fan_max=
>>>  			[HW] Maximum configurable fan speed.
>>>  
>>> +	devlink_eswitch_mode=
>>> +			[NET]
>>> +			Format:
>>> +			[<selector>]:<mode>
>>
>> It appears (please correct me if I am mistaken) that the '[' and ']'
>> above don't mean "optional" but instead they are required characters...
>>
>>> +
>>> +			<selector>:
>>> +			* | <handle>[,<handle>...]
>>
>> while here they mean "optional".
>>
>> That is confusing (inconsistent). Also, if the square brackets are
>> always required around the <selector>, what purpose do they serve?
> 
> Yes, you are right, this is confusing. The outer square brackets are part of
> the syntax and are required, while the brackets in "[,<handle>...]" mean that
> additional handles are optional.
> 
> I couldn't find a better way to describe this. What I want to say is that the
> selector is always wrapped in square brackets. Inside the brackets it can either
> be "*" to match all devices, or a comma separated list of handles. If "*" is
> not used, then at least one handle has to be provided.
> 
> Maybe it would be clearer to spell it out explicitly, something like:
> 
> Format:
>   [<selector>]:<mode>
> 
> The '[' and ']' characters are literal and required.
> 
> <selector>:
>   * | <handle>[,<handle>...]
> 
> If '*' is not used, <selector> must contain at least one <handle>.
> 
> Does that sound like a reasonable way to document it?

Yes, that helps a little bit. Better than nothing.

But why are they required at all?

>>> +
>>> +			<handle>:
>>> +			<bus-name>/<dev-name>
>>> +
>>> +			Configure default devlink eswitch mode for matching
>>> +			devlink instances during device initialization.
>>> +
>>> +			<mode>:
>>> +			legacy | switchdev | switchdev_inactive
>>> +
>>> +			Examples:
>>> +			devlink_eswitch_mode=[*]:switchdev
>>> +			devlink_eswitch_mode=[pci/0000:08:00.0]:switchdev
>>> +			devlink_eswitch_mode=[pci/0000:08:00.0,pci/0000:09:00.1]:legacy
>>> +
>>> +			See Documentation/networking/devlink/devlink-defaults.rst
>>> +			for the full syntax.
>>> +
>>>  	dfltcc=		[HW,S390]
>>>  			Format: { on | off | def_only | inf_only | always }
>>>  			on:       s390 zlib hardware support for compression on
>>
>>
> 

-- 
~Randy