linux-kernel - Re: [PATCH v3 2/2] of: property: Do not link to disabled devices

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Message-ID: <CAGETcx-g=4FQsYZ2=4wXV2EBeTAyt6182KVW2i1qroGajLgfrw@mail.gmail.com>
Date:   Mon, 20 Apr 2020 09:51:03 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] of: property: Do not link to disabled devices

On Mon, Apr 20, 2020 at 5:02 AM Nicolas Saenz Julienne
<nsaenzjulienne@...e.de> wrote:
>
> When creating a consumer/supplier relationship between two devices,
> make sure the supplier node is actually active. Otherwise this will
> create a link relationship that will never be fulfilled. This, in the
> worst case scenario, will hang the system during boot.
>
> Note that, in practice, the fact that a device-tree represented
> consumer/supplier relationship isn't fulfilled will not prevent devices
> from successfully probing.
>
> Fixes: a3e1d1a7f5fc ("of: property: Add functional dependency link from DT bindings")
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
>
> ---
>
> Changes since v2:
>  - Correct code comment
>  - Use already available return handling code
>
> Changes since v1:
>  - Move availability check into the compatible search code and stop if
>    node disabled
>
>  drivers/of/property.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index dc034eb45defd..7bcf31ba717d8 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -1045,8 +1045,20 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
>          * Find the device node that contains the supplier phandle.  It may be
>          * @sup_np or it may be an ancestor of @sup_np.
>          */
> -       while (sup_np && !of_find_property(sup_np, "compatible", NULL))
> +       while (sup_np) {
> +
> +               /* Don't allow linking to a disabled supplier */
> +               if (!of_device_is_available(sup_np)) {
> +                       of_node_put(sup_np);
> +                       sup_np = NULL;
> +               }
> +
> +               if (of_find_property(sup_np, "compatible", NULL))
> +                       break;
> +
>                 sup_np = of_get_next_parent(sup_np);
> +       }
> +
>         if (!sup_np) {
>                 dev_dbg(dev, "Not linking to %pOFP - No device\n", tmp_np);
>                 return -ENODEV;

Thanks for the fix!

Reviewed-by: Saravana Kannan <saravanak@...gle.com>