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

[Mark Bloch <mbloch@nvidia.com>]

On 04/06/2026 6:53, Randy Dunlap wrote:
> 
> 
> 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?

Jiri suggested using the square brackets, and I liked that they made the
selector look like a grouped argument. But if that is too confusing, I can
also drop them and use a simpler separator, for example:

	devlink_eswitch_mode=
			[NET]
			Format:
			<selector>=<mode>

			<selector>:
			* | <handle>[,<handle>...]

			<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=switchdev_inactive

Does this look better to you?

Mark

> 
>>>> +
>>>> +			<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
>>>
>>>
>>
>