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Subject: Re: [PATCH v1 2/2] device property: Don't clear secondary pointer for
 shared primary firmware node
To:     Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        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>
References: <20201022184100.71659-1-andriy.shevchenko@linux.intel.com>
 <20201022184100.71659-2-andriy.shevchenko@linux.intel.com>
 <20201023123544.GB614478@kuha.fi.intel.com>
From:   Ferry Toth <fntoth@gmail.com>
Message-ID: <584104f7-0d87-4070-1e67-f51f9bee0a94@gmail.com>
Date:   Fri, 23 Oct 2020 16:03:42 +0200
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Hi

Op 23-10-2020 om 14:35 schreef Heikki Krogerus:
> On Thu, Oct 22, 2020 at 09:41:00PM +0300, Andy Shevchenko wrote:
>> It appears that firmware nodes can be shared between devices. In such case
>> when a (child) device is about to be deleted, its firmware node may be shared
>> and ACPI_COMPANION_SET(..., NULL) call for it breaks the secondary link
>> of the shared primary firmware node.
>>
>> In order to prevent that, check, if the device has a parent and parent's
>> firmware node is shared with its child, and avoid crashing the link.
>>
>> Fixes: c15e1bdda436 ("device property: Fix the secondary firmware node handling in set_primary_fwnode()")
>> Reported-by: 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>

Tested-by: Ferry Toth <fntoth@gmail.com>

>> ---
>>   drivers/base/core.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>> index 41feab679fa1..78114ddac755 100644
>> --- a/drivers/base/core.c
>> +++ b/drivers/base/core.c
>> @@ -4264,6 +4264,7 @@ static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
>>    */
>>   void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>>   {
>> +	struct device *parent = dev->parent;
>>   	struct fwnode_handle *fn = dev->fwnode;
>>   
>>   	if (fwnode) {
>> @@ -4278,7 +4279,8 @@ void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>>   	} else {
>>   		if (fwnode_is_primary(fn)) {
>>   			dev->fwnode = fn->secondary;
>> -			fn->secondary = ERR_PTR(-ENODEV);
>> +			if (!(parent && fn == parent->fwnode))
>> +				fn->secondary = ERR_PTR(-ENODEV);
>>   		} else {
>>   			dev->fwnode = NULL;
>>   		}
>> -- 
>> 2.28.0