linux-kernel - Re: [PATCH v1 5/5] of: property: Delete of

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Message-ID: <CAMuHMdW_pvt1b6Y8e5j0Q5yDFMsg5z61upOo+gFaq7zf1F0V6w@mail.gmail.com>
Date:   Tue, 31 Mar 2020 14:20:27 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Len Brown <lenb@...nel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v1 5/5] of: property: Delete of_devlink kernel commandline option

Hi Saravana,

On Sat, Feb 22, 2020 at 2:41 AM Saravana Kannan <saravanak@...gle.com> wrote:
> With the addition of fw_devlink kernel commandline option, of_devlink is
> redundant and not useful anymore. So, delete it.
>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>

Thanks for your patch!

This is now commit e94f62b7140fa3da ("of: property: Delete of_devlink
kernel commandline option") upstream.

> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3299,12 +3299,6 @@
>                         This can be set from sysctl after boot.
>                         See Documentation/admin-guide/sysctl/vm.rst for details.
>
> -       of_devlink      [OF, KNL] Create device links between consumer and
> -                       supplier devices by scanning the devictree to infer the
> -                       consumer/supplier relationships.  A consumer device
> -                       will not be probed until all the supplier devices have
> -                       probed successfully.
> -
>         ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
>                         See Documentation/debugging-via-ohci1394.txt for more
>                         info.

While I agree with the thunk above...

> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 15fc9315f1a7..f104f15b57fb 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -1299,15 +1299,9 @@ static int of_link_to_suppliers(struct device *dev,
>         return ret;
>  }
>
> -static bool of_devlink;
> -core_param(of_devlink, of_devlink, bool, 0);
> -
>  static int of_fwnode_add_links(const struct fwnode_handle *fwnode,
>                                struct device *dev)
>  {
> -       if (!of_devlink)
> -               return 0;
> -
>         if (unlikely(!is_of_node(fwnode)))
>                 return 0;

... I have some reservations about removing the actual code.
The "of_devlink" kernel parameter was supported in v5.5 and v5.6, so
removing its support may silently break some setups.

Is this likely to happen?
Do we need a compatibility fallback that warns to user to update his kernel
command line?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds