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: <CAGETcx8Oc63WXy6VPNQ6uO1JhQpVFgcCYNhSJNbvDp1CD18KQg@mail.gmail.com>
Date:   Wed, 1 Sep 2021 14:53:56 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
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, Sep 1, 2021 at 8:45 AM Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> 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:

*face palm* Right. I forgot that. I just read "bus" and my mind went
to busses added as devices. It apparently also didn't help [1] which
is surprising to me. I'll dig into that separately. I'll look into
fixing this. The annoying part is that some devices have compatible
property that's both "simple-bus" and some other string that a driver
actually matches with.

-Saravana

>
> "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
> >