netdev - Re: [PATCH net-next 4/5] devlink: embed driver's priv data callback param into devlink

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Message-ID: <589aed8d-500c-4e92-91ca-492302bb2542@intel.com>
Date: Mon, 12 Aug 2024 13:50:06 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Jiri Pirko <jiri@...nulli.us>, Jakub Kicinski <kuba@...nel.org>
CC: <netdev@...r.kernel.org>, Ido Schimmel <idosch@...dia.com>, Petr Machata
	<petrm@...dia.com>, Andrew Lunn <andrew@...n.ch>, Florian Fainelli
	<f.fainelli@...il.com>, Vladimir Oltean <olteanv@...il.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Paolo
 Abeni" <pabeni@...hat.com>, Saeed Mahameed <saeedm@...dia.com>, "Leon
 Romanovsky" <leon@...nel.org>, Tariq Toukan <tariqt@...dia.com>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, <nex.sw.ncis.osdt.itp.upstreaming@...el.com>,
	Wojciech Drewek <wojciech.drewek@...el.com>
Subject: Re: [PATCH net-next 4/5] devlink: embed driver's priv data callback
 param into devlink_resource

On 8/9/24 13:02, Jiri Pirko wrote:
> Fri, Aug 09, 2024 at 04:41:50AM CEST, kuba@...nel.org wrote:
>> On Wed, 7 Aug 2024 08:49:57 +0200 Jiri Pirko wrote:
>>>> 	lockdep_assert_held(&devlink->lock);
>>>>
>>>> 	resource = devlink_resource_find(devlink, NULL, resource_id);
>>>> -	if (WARN_ON(!resource))
>>>> +	if (WARN_ON(!resource || occ_priv_size > resource->priv_size))
>>>
>>> Very odd. You allocate a mem in devl_resource_register() and here you
>>> copy data to it. Why the void pointer is not enough for you? You can
>>> easily alloc struct in the driver and pass a pointer to it.
>>>
>>> This is quite weird. Please don't.
>>
>> The patch is a bit of a half measure, true.

Another option to suit my wants would be to just pass resource_id to the
callbacks, would you accept that?

>>
>> Could you shed more light on the design choices for the resource API,
>> tho? Why the tying of objects by driver-defined IDs? It looks like
> 
> The ids are exposed all the way down to the user. They are the same
> across the reboots and allow user to use the same scripts. Similar to
> port index for example.
> 
> 
>> the callback for getting resources occupancy is "added" later once
>> the resource is registered? Is this some legacy of the old locking
>> scheme? It's quite unusual.

I did such review last month, many decisions really bother me :F, esp:
- whole thing is about limiting resources, driver asks HW for occupancy.

Some minor things:
- resizing request validation: parent asks children for permission;
- the function to commit the size after the reload is named
   devl_resource_size_get().

 From the user perspective, I'm going to add a setter, that will be
another mode of operation (if compared to the first thing on my complain
list):
+ there is a limit that is constant, and driver/user allocates resource
   from such pool.

> 
> It's been some while since I reviewed this, but afaik the reason is that
> the occupancy was not possible to obtain during reload, yet the resource
> itself stayed during reload. This is now not a problem, since
> devlink->lock protects it. I don't see why occupancy getter cannot be
> put during resource register, you are correct.
>
I could add that to my todo list