linux-kernel - Re: [PATCH v1 5/5] of: property: Skip adding device links to suppliers that aren't devices

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Message-ID: <CAGETcx_CL9P3svctyDuGpavG4Ykd+o2G-rxDAE5OUvxL+sj6xA@mail.gmail.com>
Date:   Mon, 4 Nov 2019 11:01:44 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Len Brown <lenb@...nel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v1 5/5] of: property: Skip adding device links to
 suppliers that aren't devices

On Mon, Nov 4, 2019 at 7:18 AM Rob Herring <robh+dt@...nel.org> wrote:
>
> On Mon, Oct 28, 2019 at 5:00 PM Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > Some devices need to be initialized really early and can't wait for
> > driver core or drivers to be functional.  These devices are typically
> > initialized without creating a struct device for their device nodes.
> >
> > If a supplier ends up being one of these devices, skip trying to add
> > device links to them.
> >
> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > ---
> >  drivers/of/property.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/of/property.c b/drivers/of/property.c
> > index f16f85597ccc..21c9d251318a 100644
> > --- a/drivers/of/property.c
> > +++ b/drivers/of/property.c
> > @@ -1038,6 +1038,7 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
> >         struct device *sup_dev;
> >         int ret = 0;
> >         struct device_node *tmp_np = sup_np;
> > +       int is_populated;
> >
> >         of_node_get(sup_np);
> >         /*
> > @@ -1062,9 +1063,10 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
> >                 return -EINVAL;
> >         }
> >         sup_dev = get_dev_from_fwnode(&sup_np->fwnode);
> > +       is_populated = of_node_check_flag(sup_np, OF_POPULATED);
> >         of_node_put(sup_np);
> >         if (!sup_dev)
> > -               return -EAGAIN;
> > +               return is_populated ? 0 : -EAGAIN;
>
> You're only using the flag in one spot and a comment would be good
> here, so I'd just do:
>
> if (of_node_check_flag(sup_np, OF_POPULATED))
>         return 0; /* Early device without a struct device */

Hi Rob,

Thanks for the review.

I'm using the flag to keep the error handling code simple/cleaner. I
can't do the check like that after I do a put on the sup_np.

Yeah, I was actually planning to add a dev_dbg() message when this
happens and returning a -EINVAL (that'll be ignored by the caller)
instead of -EAGAIN (that's NOT ignored by the caller).

Looks like these changes go pulled into driver-core-next. So I'll send
a delta patch to add the dbg message and also address you nit on the
other patch.

Thanks,
Saravana