netdev - Re: [RFC PATCH fwctl 5/5] pds_fwctl: add Documentation entries

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Message-ID: <cdf30ddd-6d88-4fd7-877e-1a15a7cc5ec6@amd.com>
Date: Thu, 13 Feb 2025 15:18:54 -0800
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: jgg@...dia.com, andrew.gospodarek@...adcom.com,
 aron.silverton@...cle.com, dan.j.williams@...el.com, daniel.vetter@...ll.ch,
 dave.jiang@...el.com, dsahern@...nel.org, gospo@...adcom.com,
 hch@...radead.org, itayavr@...dia.com, jiri@...dia.com, kuba@...nel.org,
 lbloch@...dia.com, leonro@...dia.com, saeedm@...dia.com,
 linux-cxl@...r.kernel.org, linux-rdma@...r.kernel.org,
 netdev@...r.kernel.org, brett.creeley@....com
Subject: Re: [RFC PATCH fwctl 5/5] pds_fwctl: add Documentation entries

On 2/12/2025 4:51 AM, Jonathan Cameron wrote:
> 
> On Tue, 11 Feb 2025 15:48:54 -0800
> Shannon Nelson <shannon.nelson@....com> wrote:
> 
>> Add pds_fwctl to the driver and fwctl documentation pages.
>>
>> Signed-off-by: Shannon Nelson <shannon.nelson@....com>
>> ---
>>   Documentation/userspace-api/fwctl/fwctl.rst   |  1 +
>>   Documentation/userspace-api/fwctl/index.rst   |  1 +
>>   .../userspace-api/fwctl/pds_fwctl.rst         | 41 +++++++++++++++++++
>>   3 files changed, 43 insertions(+)
>>   create mode 100644 Documentation/userspace-api/fwctl/pds_fwctl.rst
>>
>> diff --git a/Documentation/userspace-api/fwctl/fwctl.rst b/Documentation/userspace-api/fwctl/fwctl.rst
>> index 428f6f5bb9b4..72853b0d3dc8 100644
>> --- a/Documentation/userspace-api/fwctl/fwctl.rst
>> +++ b/Documentation/userspace-api/fwctl/fwctl.rst
>> @@ -150,6 +150,7 @@ fwctl User API
>>
>>   .. kernel-doc:: include/uapi/fwctl/fwctl.h
>>   .. kernel-doc:: include/uapi/fwctl/mlx5.h
>> +.. kernel-doc:: include/uapi/fwctl/pds.h
>>
>>   sysfs Class
>>   -----------
>> diff --git a/Documentation/userspace-api/fwctl/index.rst b/Documentation/userspace-api/fwctl/index.rst
>> index 06959fbf1547..12a559fcf1b2 100644
>> --- a/Documentation/userspace-api/fwctl/index.rst
>> +++ b/Documentation/userspace-api/fwctl/index.rst
>> @@ -10,3 +10,4 @@ to securely construct and execute RPCs inside device firmware.
>>      :maxdepth: 1
>>
>>      fwctl
>> +   pds_fwctl
>> diff --git a/Documentation/userspace-api/fwctl/pds_fwctl.rst b/Documentation/userspace-api/fwctl/pds_fwctl.rst
>> new file mode 100644
>> index 000000000000..9fb1b4ac0a5e
>> --- /dev/null
>> +++ b/Documentation/userspace-api/fwctl/pds_fwctl.rst
>> @@ -0,0 +1,41 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +================
>> +fwctl pds driver
>> +================
>> +
>> +:Author: Shannon Nelson
>> +
>> +Overview
>> +========
>> +
>> +The PDS Core device makes an fwctl service available through an
>> +auxiliary_device named pds_core.fwctl.N.  The pds_fwctl driver binds
>> +to this device and registers itself with the fwctl bus.  The resulting
>> +userspace interface is used by an application that is a part of the
>> +AMD/Pensando software package for the Distributed Service Card (DSC).
> 
> Jason, where did we get to on the question of a central open repo etc?
> 
>> +
>> +The pds_fwctl driver has little knowledge of the firmware's internals,
>> +only knows how to send adminq commands for fwctl requests.  The set of
>> +operations available through this interface depends on the firmware in
>> +the DSC, and the userspace application version must match the firmware
>> +so that they can talk to each other.
>> +
>> +This set of available operations is not known to the pds_fwctl driver.
>> +When a connection is created the pds_fwctl driver requests from the
>> +firmware list of endpoints and a list of operations for each endpoint.
>> +This list of operations includes a minumum scope level that the pds_fwctl
>> +driver can use for filtering privilege levels.
> 
> Ah. Ok. So the scope is provided in the replies to these queries.
> Do we have anything to verify that today?
> Also, I wasn't sure when reading driver on whether the operations list
> is dynamic or something we can read once and cache?

We request the operations list once on the first query of each endpoint 
and cache them for the next time.

> 
>> +
>> +pds_fwctl User API
>> +==================
>> +
>> +.. kernel-doc:: include/uapi/fwctl/pds.h
>> +
>> +Each RPC request includes the target endpoint and the operation id, and in
>> +and out buffer lengths and pointers.  The driver verifies the existence
>> +of the requested endpoint and operations, then checks the current scope
>> +against the required scope of the operation.  The adminq request is then
> 
> Spell out admin q (or is that a typo?)

The "adminq" is the particular object name, so I'll keep that, but I can 
certainly add a little more text around it.

Thanks for your review comments, we appreciate it!

Cheers,
sln


> 
>> +put together with the request data and sent to the firmware, and the
>> +results are returned to the caller.
>> +
>