linux-kernel - Re: [PATCH v2 08/17] driver core: Add fwnode link support

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Message-ID: <20201206074840.GB687065@unreal>
Date:   Sun, 6 Dec 2020 09:48:40 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        kernel-team@...roid.com, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 08/17] driver core: Add fwnode link support

On Fri, Nov 20, 2020 at 06:02:23PM -0800, Saravana Kannan wrote:
> Add support for creating supplier-consumer links between fwnodes.  It is
> intended for internal use the driver core and generic firmware support
> code (eg. Device Tree, ACPI), so it is simple by design and the API
> provided is limited.
>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/base/core.c    | 98 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/of/dynamic.c   |  1 +
>  include/linux/fwnode.h | 14 ++++++
>  3 files changed, 113 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 401fa7e3505c..e2b246a44d1a 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -50,6 +50,104 @@ static LIST_HEAD(wait_for_suppliers);
>  static DEFINE_MUTEX(wfs_lock);
>  static LIST_HEAD(deferred_sync);
>  static unsigned int defer_sync_state_count = 1;
> +static DEFINE_MUTEX(fwnode_link_lock);
> +
> +/**
> + * fwnode_link_add - Create a link between two fwnode_handles.
> + * @con: Consumer end of the link.
> + * @sup: Supplier end of the link.
> + *
> + * Create a fwnode link between fwnode handles @con and @sup. The fwnode link
> + * represents the detail that the firmware lists @sup fwnode as supplying a
> + * resource to @con.
> + *
> + * The driver core will use the fwnode link to create a device link between the
> + * two device objects corresponding to @con and @sup when they are created. The
> + * driver core will automatically delete the fwnode link between @con and @sup
> + * after doing that.
> + *
> + * Attempts to create duplicate links between the same pair of fwnode handles
> + * are ignored and there is no reference counting.

Sorry to ask, but why is that?
Isn't this a programmer error?

Thanks