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

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Date:   Fri, 23 Oct 2020 16:16:21 +0200
From:   Ferry Toth <fntoth@...il.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Saravana Kannan <saravanak@...gle.com>,
        linux-acpi@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v1 1/2] device property: Keep secondary firmware node
 secondary by type

Hi

Op 23-10-2020 om 14:34 schreef Heikki Krogerus:
> 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@...il.com>
>> Signed-off-by: Andy Shevchenko<andriy.shevchenko@...ux.intel.com>
> FWIW:
>
> Reviewed-by: Heikki Krogerus<heikki.krogerus@...ux.intel.com>
> Tested-by: Ferry Toth<fntoth@...il.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