linux-kernel - Re: [PATCH net-next V3 02/14] documentation: networking: add shared devlink documentation

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Message-ID: <e6ad8812-d59b-40ae-8404-4babf88ec14d@infradead.org>
Date: Mon, 24 Nov 2025 15:02:08 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Tariq Toukan <tariqt@...dia.com>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>
Cc: Donald Hunter <donald.hunter@...il.com>, Jiri Pirko <jiri@...nulli.us>,
 Jonathan Corbet <corbet@....net>, Saeed Mahameed <saeedm@...dia.com>,
 Leon Romanovsky <leon@...nel.org>, Mark Bloch <mbloch@...dia.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-rdma@...r.kernel.org,
 Gal Pressman <gal@...dia.com>, Moshe Shemesh <moshe@...dia.com>,
 Carolina Jubran <cjubran@...dia.com>, Cosmin Ratiu <cratiu@...dia.com>,
 Jiri Pirko <jiri@...dia.com>
Subject: Re: [PATCH net-next V3 02/14] documentation: networking: add shared
 devlink documentation



On 11/24/25 2:27 PM, Tariq Toukan wrote:
> From: Jiri Pirko <jiri@...dia.com>
> 
> Document shared devlink instances for multiple PFs on the same chip.
> 
> Signed-off-by: Jiri Pirko <jiri@...dia.com>
> Reviewed-by: Cosmin Ratiu <cratiu@...dia.com>
> Signed-off-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  .../networking/devlink/devlink-shared.rst     | 66 +++++++++++++++++++
>  Documentation/networking/devlink/index.rst    |  1 +
>  2 files changed, 67 insertions(+)
>  create mode 100644 Documentation/networking/devlink/devlink-shared.rst
> 
> diff --git a/Documentation/networking/devlink/devlink-shared.rst b/Documentation/networking/devlink/devlink-shared.rst
> new file mode 100644
> index 000000000000..8377d524998f
> --- /dev/null
> +++ b/Documentation/networking/devlink/devlink-shared.rst
> @@ -0,0 +1,66 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +============================
> +Devlink Shared Instances
> +============================
> +
> +Overview
> +========
> +
> +Shared devlink instances allow multiple physical functions (PFs) on the same
> +chip to share an additional devlink instance for chip-wide operations. This
> +should be implemented within individual drivers alongside the individual PF
> +devlink instances, not replacing them.
> +
> +The shared devlink instance should be backed by a faux device and should
> +provide a common interface for operations that affect the entire chip
> +rather than individual PFs.
> +
> +Implementation
> +==============
> +
> +Architecture
> +------------
> +
> +The implementation should use:
> +
> +* **Faux device**: Virtual device backing the shared devlink instance
> +* **Chip identification**: PFs are grouped by chip using a driver-specific identifier
> +* **Shared instance management**: Global list of shared instances with reference counting
> +
> +Initialization Flow
> +-------------------
> +
> +1. **PF calls shared devlink init** during driver probe
> +2. **Chip identification** using driver-specific method to determine device identity
> +3. **Lookup existing shared instance** for this chip identifier
> +4. **Create new shared instance** if none exists:
> +
> +   * Create faux device with chip identifier as name
> +   * Allocate and register devlink instance
> +   * Add to global shared instances list
> +
> +5. **Add PF to shared instance** PF list
> +6. **Set nested devlink instance** dor the PF devlink instance

s/dor/for/

> +
> +Cleanup Flow
> +------------
> +
> +1. **Cleanup** when PF is removed; destroy shared instance when last PF is removed
> +
> +Chip Identification
> +-------------------
> +
> +PFs belonging to the same chip are identified using a driver-specific method.
> +The driver is free to choose any identifier that is suitable for determining
> +whether two PFs are part of the same device. Examples include VPD serial numbers,
> +device tree properties, or other hardware-specific identifiers.
> +
> +Locking
> +-------
> +
> +A global per-driver mutex protects the shared instances list and individual shared
> +instance PF lists during registration/deregistration.
> +
> +Similarly to other nested devlink instance relationships, devlink lock of
> +the shared instance should be always taken after the devlink lock of PF.


-- 
~Randy