linux-kernel - Re: [PATCH 1/1] driver core: Keep the supplier fwnode consistent with the device

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Date:   Fri, 10 Nov 2023 17:50:07 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Herve Codina <herve.codina@...tlin.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org,
        Allan Nielsen <allan.nielsen@...rochip.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Steen Hegelund <steen.hegelund@...rochip.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/1] driver core: Keep the supplier fwnode consistent with
 the device

On Thu, Nov 9, 2023 at 11:56 PM Herve Codina <herve.codina@...tlin.com> wrote:
>
> The commit 3a2dbc510c43 ("driver core: fw_devlink: Don't purge child
> fwnode's consumer links") introduces the possibility to use the
> supplier's parent device instead of the supplier itself.
> In that case the supplier fwnode used is not updated and is no more
> consistent with the supplier device used.
>
> Update the fwnode used to be consistent with the supplier device used.
>
> Fixes: 3a2dbc510c43 ("driver core: fw_devlink: Don't purge child fwnode's consumer links")
> Cc: stable@...r.kernel.org
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> ---
>  drivers/base/core.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 4d8b315c48a1..17f2568e0a79 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2076,6 +2076,18 @@ static int fw_devlink_create_devlink(struct device *con,
>                 sup_dev = get_dev_from_fwnode(sup_handle);
>
>         if (sup_dev) {
> +               /*
> +                * The supplier device may have changed and so, the supplier
> +                * fwnode maybe inconsistent.
> +                * Update the supplier fwnode
> +                */
> +               sup_handle = sup_dev->fwnode;
> +               if (!sup_handle) {
> +                       dev_dbg(con, "Not linking %s - fwnode NULL\n",
> +                               dev_name(sup_dev));
> +                       goto out;
> +               }
> +

Nack. It's easier to debug when you know what supplier you were
pointing to in DT that triggered the creation of the device link. The
parent could be several levels up and multiple supplier links might be
skipped for various reasons. If they all printed the parent's fwnode,
it'll be confusing to debug.

-Saravana

>                 /*
>                  * If it's one of those drivers that don't actually bind to
>                  * their device using driver core, then don't wait on this
> --
> 2.41.0
>