netdev - Re: [Intel-wired-lan] [PATCH iwl-next v4 4/5] ice: Add tx_scheduling

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Date: Tue, 27 Feb 2024 13:17:44 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Mateusz Polchlopek <mateusz.polchlopek@...el.com>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	horms@...nel.org, przemyslaw.kitszel@...el.com,
	Lukasz Czapnik <lukasz.czapnik@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH iwl-next v4 4/5] ice: Add
 tx_scheduling_layers devlink param

Tue, Feb 27, 2024 at 03:37:00AM CET, kuba@...nel.org wrote:
>On Sun, 25 Feb 2024 08:18:00 +0100 Jiri Pirko wrote:
>> >Do you recall any specific param that got rejected from mlx5?
>> >Y'all were allowed to add the eq sizing params, which I think
>> >is not going to be mlx5-only for long. Otherwise I only remember
>> >cases where I'd try to push people to use the resource API, which
>> >IMO is better for setting limits and delegating resources.  
>> 
>> I don't have anything solid in mind, I would have to look it up. But
>> there is certainly quite big amount of uncertainties among my
>> colleagues to jundge is some param would or would not be acceptable to
>> you. That's why I believe it would save a lot of people time to write
>> the policy down in details, with examples, etc. Could you please?
>
>How about this? (BTW took me half an hour to write, just in case 
>you're wondering)
>
>diff --git a/Documentation/networking/devlink/devlink-params.rst b/Documentation/networking/devlink/devlink-params.rst
>index 4e01dc32bc08..f1eef6d065be 100644
>--- a/Documentation/networking/devlink/devlink-params.rst
>+++ b/Documentation/networking/devlink/devlink-params.rst
>@@ -9,10 +9,12 @@ level device functionality. Since devlink can operate at the device-wide
> level, it can be used to provide configuration that may affect multiple
> ports on a single device.
> 
>-This document describes a number of generic parameters that are supported
>-across multiple drivers. Each driver is also free to add their own
>-parameters. Each driver must document the specific parameters they support,
>-whether generic or not.
>+There are two categories of devlink parameters - generic parameters
>+and device-specific quirks. Generic devlink parameters are configuration
>+knobs which don't fit into any larger API, but are supported across multiple
>+drivers. This document describes a number of generic parameters.
>+Each driver can also add its own parameters, which are documented in driver
>+specific files.
> 
> Configuration modes
> ===================
>@@ -137,3 +139,32 @@ own name.
>    * - ``event_eq_size``
>      - u32
>      - Control the size of asynchronous control events EQ.
>+
>+Adding new params
>+=================
>+
>+Addition of new devlink params is carefully scrutinized upstream.
>+More complete APIs (in devlink, ethtool, netdev etc.) are always preferred,
>+devlink params should never be used in their place e.g. to allow easier
>+delivery via out-of-tree modules, or to save development time.
>+
>+devlink parameters must always be thoroughly documented, both from technical
>+perspective (to allow meaningful upstream review), and from user perspective
>+(to allow users to make informed decisions).
>+
>+The requirements above should make it obvious that any "automatic" /
>+"pass-through" registration of devlink parameters, based on strings
>+read from the device, will not be accepted.
>+
>+There are two broad categories of devlink params which had been accepted
>+in the past:
>+
>+ - device-specific configuration knobs, which cannot be inferred from
>+   other device configuration. Note that the author is expected to study
>+   other drivers to make sure that the configuration is in fact unique
>+   to the implementation.
>+
>+ - configuration which must be set at device initialization time.
>+   Allowing user to enable features at runtime is always preferable
>+   but in reality most devices allow certain features to be enabled/disabled
>+   only by changing configuration stored in NVM.

Looks like most of the generic params does not fit either of these 2
categories. Did you mean these 2 categories for driver specific?