linux-kernel - Re: [PATCH v1] driver core: fw_devlink: Don't create device links for devices not on a bus

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Message-ID: <CAPDyKFpQqKx2UDo4kc3eAxPfp47gOGbjtnm0fg1q+bshpb-vew@mail.gmail.com>
Date:   Wed, 1 Sep 2021 17:44:51 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] driver core: fw_devlink: Don't create device links for
 devices not on a bus

On Wed, 1 Sept 2021 at 00:45, Saravana Kannan <saravanak@...gle.com> wrote:
>
> Devices that are not on a bus will never have a driver bound to it. So,
> fw_devlink should not create device links for it as it can cause probe
> issues[1] or sync_state() call back issues[2].
>
> [1] - https://lore.kernel.org/lkml/CAGETcx_xJCqOWtwZ9Ee2+0sPGNLM5=F=djtbdYENkAYZa0ynqQ@mail.gmail.com/
> [2] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@mail.gmail.com/

Unfortunately, this doesn't fix my problem in [2].

When the "soctest" device is initialized, via of_platform_populate(),
it will be attached to the platform bus, hence the check for the bus
pointer that you suggest to add below, doesn't have an impact on my
use case. I still get the below in the log:

"platform soctest: Linked as a sync state only consumer to pm_domain_test"

Kind regards
Uffe

> Fixes: f9aa460672c9 ("driver core: Refactor fw_devlink feature")
> Reported-by: Ulf Hansson <ulf.hansson@...aro.org>
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/base/core.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index f6360490a4a3..304a06314656 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -1719,8 +1719,24 @@ static int fw_devlink_create_devlink(struct device *con,
>         struct device *sup_dev;
>         int ret = 0;
>
> +       /*
> +        * If a consumer device is not on a bus (i.e. a driver will never bind
> +        * to it), it doesn't make sense for fw_devlink to create device links
> +        * for it.
> +        */
> +       if (con->bus == NULL)
> +               return -EINVAL;
> +
>         sup_dev = get_dev_from_fwnode(sup_handle);
>         if (sup_dev) {
> +               /*
> +                * If a supplier device is not on a bus (i.e. a driver will
> +                * never bind to it), it doesn't make sense for fw_devlink to
> +                * create device links for it.
> +                */
> +               if (sup_dev->bus == NULL)
> +                       return -EINVAL;
> +
>                 /*
>                  * If it's one of those drivers that don't actually bind to
>                  * their device using driver core, then don't wait on this
> --
> 2.33.0.259.gc128427fd7-goog
>