Subject: Re: Linux-3.14-rc2: Order of serial node compatibles in DTS files.

From: Sebastian Hesselbarth <[email-masked]>
Date: Wed, 12 Feb 2014 12:26:14 +0100

On 02/12/14 11:31, Kevin Hao wrote:
> On Wed, Feb 12, 2014 at 09:30:00AM +0100, Sebastian Hesselbarth wrote:
>> On 02/12/2014 06:28 AM, Kevin Hao wrote:
>>> On Wed, Feb 12, 2014 at 10:21:58AM +1000, Stephen N Chivers wrote:
>>>> But, the Interrupt Controller (MPIC)
>>>> goes AWOL and it is down hill from there.
>>>>
>>>> The MPIC is specified in the DTS as:
>>>>
>>>>          mpic: pic@40000 {
>>>>                          interrupt-controller;
>>>>                          #address-cells = <0>;
>>>>                          #interrupt-cells = <2>;
>>>>                          reg = <0x40000 0x40000>;
>>>>                          compatible = "chrp,open-pic";
>>>>                          device_type = "open-pic";
>>>>                          big-endian;
>>>>                  };
>>>>
>>>> The board support file has the standard mechanism for allocating
>>>> the PIC:
>>>>
>>>>          struct mpic *mpic;
>>>>
>>>>          mpic = mpic_alloc(NULL, 0, 0, 0, 256, " OpenPIC  ");
>>>>          BUG_ON(mpic == NULL);
>>>>
>>>>          mpic_init(mpic);
>>>>
>>>> I checked for damage in applying the patch and it has applied
>>>> correctly.
>>>
>>> How about the following fix?
>>>
>>> diff --git a/drivers/of/base.c b/drivers/of/base.c
>>> index ff85450d5683..ca91984d3c4b 100644
>>> --- a/drivers/of/base.c
>>> +++ b/drivers/of/base.c
>>> @@ -730,32 +730,40 @@ out:
>>>   }
>>>   EXPORT_SYMBOL(of_find_node_with_property);
>>>
>>> +static int of_match_type_name(const struct device_node *node,
>>> +				const struct of_device_id *m)
>>
>> I am fine with having a sub-function here, but it should rather be
>> named of_match_type_or_name.
>
> OK.
>
>>
>>> +{
>>> +	int match = 1;
>>> +
>>> +	if (m->name[0])
>>> +		match &= node->name && !strcmp(m->name, node->name);
>>> +
>>> +	if (m->type[0])
>>> +		match &= node->type && !strcmp(m->type, node->type);
>>> +
>>> +	return match;
>>> +}
>> [...]
>>> +	/* Check against matches without compatible string */
>>> +	m = matches;
>>> +	while (!m->compatible[0] && (m->name[0] || m->type[0])) {
>>
>> We shouldn't check for anything else than the sentinel here.
>> Although I guess yours will not quit early as mine did but that
>> way we don't have to worry about it.
>
> Yes, this is still buggy. I will change something like this:
>
> 	m = matches;
> 	/* Check against matches without compatible string */
> 	while (m->name[0] || m->type[0] || m->compatible[0]) {
> 		if (m->compatible[0]) {
> 			m++;
> 			continue;
> 		}
>
> 		match = of_match_type_name(node, m);
> 		if (match)
> 			return m;
> 		m++;
> 	}

You can cook it down to:

	m = matches;
	/* Check against matches without compatible string */
	while (m->name[0] || m->type[0] || m->compatible[0]) {
		if (!m->compatible[0] && of_match_type_or_name(node, m)
			return m;
		m++;
	}