linux-kernel - Re: [PATCH v2 3/4] driver core: Add fw_devlink.timeout param to stop waiting for devlinks

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Message-ID: <20221117151949.3cbc6cwphnv4scze@halaney-x13s>
Date:   Thu, 17 Nov 2022 09:19:49 -0600
From:   Andrew Halaney <ahalaney@...hat.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-arm-msm@...r.kernel.org, John Stultz <jstultz@...gle.com>,
        Peter Robinson <pbrobinson@...hat.com>,
        Steev Klimaszewski <steev@...i.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Enric Balletbo i Serra <eballetbo@...hat.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Brian Masney <bmasney@...hat.com>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v2 3/4] driver core: Add fw_devlink.timeout param to stop
 waiting for devlinks

On Wed, Nov 16, 2022 at 01:01:59PM +0100, Javier Martinez Canillas wrote:
> Currently, the probe deferral timeout does two things:
> 
> 1) Call to fw_devlink_drivers_done() to relax the device dependencies and
>    allow drivers to be probed if these dependencies are optional.
> 
> 2) Disable the probe deferral mechanism so that drivers will fail to probe
>    if the required dependencies are not present, instead of adding them to
>    the deferred probe pending list.
> 
> But there is no need to couple these two, for example the probe deferral
> can be used even when the device links are disable (i.e: fw_devlink=off).
> 
> So let's add a separate fw_devlink.timeout command line parameter to allow
> relaxing the device links and prevent drivers to wait for these to probe.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> ---
> 
> (no changes since v1)
> 
>  .../admin-guide/kernel-parameters.txt         |  7 ++++
>  drivers/base/dd.c                             | 38 ++++++++++++++++++-
>  2 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index a465d5242774..38138a44d5ed 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1581,6 +1581,13 @@
>  			dependencies. This only applies for fw_devlink=on|rpm.
>  			Format: <bool>
>  
> +	fw_devlink.timeout=

Just thought about this, but I think this should be called
fw_devlink_timeout. Generally the $MODULE.$PARAM syntax is reserved for
things that can be specificed with module_param().

The advantage is if you accidentally type say fw_devlink_timeut=10 the
kernel logs will indicate it has no clue what that means. Including the
"." makes the kernel assume that maybe a future module name fw_devlink
will be loaded, and at that time will see if that module has the
parameter mentioned. A little thing but I think work changing in v3.

Thanks,
Andrew