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

Zijun Hu
2024-08-20T13:40:39Z

On 2024/8/20 20:53, Ira Weiny wrote:
> Zijun Hu wrote:
>> From: Zijun Hu <quic_zijuhu@quicinc.com>
>>
>> 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@quicinc.com
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@quicinc.com>
>> ---
>> 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
>>
>
>