linux-kernel - Re: [PATCH v1 1/2] device property: Keep secondary firmware node secondary by type

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Message-ID: <CAJZ5v0h5DF5g5TvO+sZWmJyBi=Z09EbiCkkn=jGwV3e2gM_HAQ@mail.gmail.com>
Date:   Tue, 27 Oct 2020 19:21:57 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Saravana Kannan <saravanak@...gle.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Ferry Toth <fntoth@...il.com>
Subject: Re: [PATCH v1 1/2] device property: Keep secondary firmware node
 secondary by type

On Thu, Oct 22, 2020 at 8:41 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> Behind primary and secondary we understand the type of the nodes
> which might define their ordering. However, if primary node gone,
> we can't maintain the ordering by definition of the linked list.
> Thus, by ordering secondary node becomes first in the list.
> But in this case the meaning of it is still secondary (or auxiliary).
> The type of the node is maintained by the secondary pointer in it:
>
>         secondary pointer               Meaning
>         NULL or valid                   primary node
>         ERR_PTR(-ENODEV)                secondary node
>
> So, if by some reason we do the following sequence of calls
>
>         set_primary_fwnode(dev, NULL);
>         set_primary_fwnode(dev, primary);
>
> we should preserve secondary node.
>
> This concept is supported by the description of set_primary_fwnode()
> along with implementation of set_secondary_fwnode(). Hence, fix
> the commit c15e1bdda436 to follow this as well.
>
> Fixes: c15e1bdda436 ("device property: Fix the secondary firmware node handling in set_primary_fwnode()")
> Cc: Ferry Toth <fntoth@...il.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/base/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index c852f16c111b..41feab679fa1 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4278,7 +4278,7 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>         } else {
>                 if (fwnode_is_primary(fn)) {
>                         dev->fwnode = fn->secondary;
> -                       fn->secondary = NULL;
> +                       fn->secondary = ERR_PTR(-ENODEV);
>                 } else {
>                         dev->fwnode = NULL;
>                 }
> --

Applied as 5.10-rc material along with the [2/2], thanks!