Re: [PATCH v2 1/4] driver core: Make parameter check consistent for API cluster device_(for_each|find)_child()

[Zijun Hu]

On 2024/8/20 20:53, Ira Weiny wrote:
> Zijun Hu wrote:
>> From: Zijun Hu <quic_zijuhu@xxxxxxxxxxx>
>>
>> The following API cluster takes the same type parameter list, but do not
>> have consistent parameter check as shown below.
>>
>> device_for_each_child(struct device *parent, ...)  // check (!parent->p)
>> device_for_each_child_reverse(struct device *parent, ...) // same as above
>> device_find_child(struct device *parent, ...)      // check (!parent)
>>
> 
> Seems reasonable.
> 
> What about device_find_child_by_name()?
> 

Plan to simplify this API implementation by * atomic * API
device_find_child() as following:

https://lore.kernel.org/all/20240811-simply_api_dfcbn-v2-1-d0398acdc366@xxxxxxxxxxx
struct device *device_find_child_by_name(struct device *parent,
 					 const char *name)
{
	return device_find_child(parent, name, device_match_name);
}

>> Fixed by using consistent check (!parent || !parent->p) for the cluster.
>>
>> Signed-off-by: Zijun Hu <quic_zijuhu@xxxxxxxxxxx>
>> ---
>>  drivers/base/core.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>> index 1688e76cb64b..b1dd8c5590dc 100644
>> --- a/drivers/base/core.c
>> +++ b/drivers/base/core.c
>> @@ -4004,7 +4004,7 @@ int device_for_each_child(struct device *parent, void *data,
>>  	struct device *child;
>>  	int error = 0;
>>  
>> -	if (!parent->p)
>> +	if (!parent || !parent->p)
>>  		return 0;
>>  
>>  	klist_iter_init(&parent->p->klist_children, &i);
>> @@ -4034,7 +4034,7 @@ int device_for_each_child_reverse(struct device *parent, void *data,
>>  	struct device *child;
>>  	int error = 0;
>>  
>> -	if (!parent->p)
>> +	if (!parent || !parent->p)
>>  		return 0;
>>  
>>  	klist_iter_init(&parent->p->klist_children, &i);
>> @@ -4068,7 +4068,7 @@ struct device *device_find_child(struct device *parent, void *data,
>>  	struct klist_iter i;
>>  	struct device *child;
>>  
>> -	if (!parent)
>> +	if (!parent || !parent->p)
> 
> Perhaps this was just a typo which should have been.
> 
> 	if (!parent->p)
> ?
> 
maybe, but the following device_find_child_by_name() also use (!parent).

> I think there is an expectation that none of these are called with a NULL
> parent.
>

this patch aim is to make these atomic APIs have consistent checks as
far as possible, that will make other patches within this series more
acceptable.

i combine two checks to (!parent || !parent->p) since i did not know
which is better.

> Ira
> 
>>  		return NULL;
>>  
>>  	klist_iter_init(&parent->p->klist_children, &i);
>>
>> -- 
>> 2.34.1
>>
> 
>