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Date:   Fri, 23 Oct 2020 15:34:12 +0300
From:   Heikki Krogerus <heikki.krogerus@linux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org,
        Saravana Kannan <saravanak@google.com>,
        linux-acpi@vger.kernel.org,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Ferry Toth <fntoth@gmail.com>
Subject: Re: [PATCH v1 1/2] device property: Keep secondary firmware node
 secondary by type
Message-ID: <20201023123412.GA614478@kuha.fi.intel.com>
References: <20201022184100.71659-1-andriy.shevchenko@linux.intel.com>
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In-Reply-To: <20201022184100.71659-1-andriy.shevchenko@linux.intel.com>
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On Thu, Oct 22, 2020 at 09:40:59PM +0300, Andy Shevchenko 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@gmail.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.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;
>  		}
> -- 
> 2.28.0

-- 
heikki