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

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Message-ID: <20231113103820.7b04f5d0@bootlin.com>
Date:   Mon, 13 Nov 2023 10:38:20 +0100
From:   Herve Codina <herve.codina@...tlin.com>
To:     Saravana Kannan <saravanak@...gle.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

Hi Saravana,

On Fri, 10 Nov 2023 17:50:07 -0800
Saravana Kannan <saravanak@...gle.com> wrote:

> 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.

In fact, I will remove the check if(!sup_handle) in the next iteration.

Indeed, sup_handle cannot be NULL.
sup_dev is retrieved from fwnode_get_next_parent_dev() or get_dev_from_fwnode().
In both cases, if sup_dev is valid, sup_dev->fwnode is valid too.
So, the check and the dev_dbg() call make no sense.

Best regards,
Hervé