How to get the hci_dev from an adv instance's work struct in a linked list?

How to get the hci_dev from an adv instance's work struct in a linked list?

[Florian Grandel]

Hi!

I got quite far today refactoring from

struct hci_dev { ... struct adv_info adv_instance; ... };

to

struct hci_dev { ... struct list_head adv_instances; ... };

But in the end I got stuck on refactoring the adv timeout callback. 
Originally it looked like this:

static void adv_timeout_expired(struct work_struct *work)
{
   struct hci_dev *hdev = container_of(work, struct hci_dev,
                                       adv_instance.timeout_exp.work);
   ...
}

But now I would have to construct a pointer to the hci_dev struct from a 
list entry:

static void adv_timeout_expired(struct work_struct *work)
{
   struct adv_info *adv_instance = container_of(work, struct adv_info,
                                                timeout_exp.work);
   ...
}

I couldn't find a way to get the list head of the adv info list entry so 
that I could retrieve its containing hci_dev structure, though.

How would I construct the required hci_dev struct from the work pointer 
in this case? Any ideas?

Florian

Re: How to get the hci_dev from an adv instance's work struct in a linked list?

[Arman Uguray]

Hi Florian,

> On Wed, Apr 1, 2015 at 7:13 PM, Florian Grandel <fgrandel@gmail.com> wrote:
> Hi!
>
> I got quite far today refactoring from
>
> struct hci_dev { ... struct adv_info adv_instance; ... };
>
> to
>
> struct hci_dev { ... struct list_head adv_instances; ... };
>
> But in the end I got stuck on refactoring the adv timeout callback.
> Originally it looked like this:
>
> static void adv_timeout_expired(struct work_struct *work)
> {
>   struct hci_dev *hdev = container_of(work, struct hci_dev,
>                                       adv_instance.timeout_exp.work);
>   ...
> }
>
> But now I would have to construct a pointer to the hci_dev struct from a
> list entry:
>
> static void adv_timeout_expired(struct work_struct *work)
> {
>   struct adv_info *adv_instance = container_of(work, struct adv_info,
>                                                timeout_exp.work);
>   ...
> }
>
> I couldn't find a way to get the list head of the adv info list entry so
> that I could retrieve its containing hci_dev structure, though.
>

Once simple solution is to add a struct hci_dev pointer to struct
adv_info. Once you get the pointer to the instance then you can obtain
the hci_dev pointer that way.

> How would I construct the required hci_dev struct from the work pointer in
> this case? Any ideas?
>
> Florian
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Thanks,
Arman

Re: How to get the hci_dev from an adv instance's work struct in a linked list?

[Florian Grandel]

Hi Arman,

it's impressive how responsive you are on this list here. Really cool. :-)

 >> I got quite far today refactoring from
>>
>> struct hci_dev { ... struct adv_info adv_instance; ... };
>>
>> to
>>
>> struct hci_dev { ... struct list_head adv_instances; ... };
>>
>> But in the end I got stuck on refactoring the adv timeout callback.
>> Originally it looked like this:
>>
>> static void adv_timeout_expired(struct work_struct *work)
>> {
>>    struct hci_dev *hdev = container_of(work, struct hci_dev,
>>                                        adv_instance.timeout_exp.work);
>>    ...
>> }
>>
>> But now I would have to construct a pointer to the hci_dev struct from a
>> list entry:
>>
>> static void adv_timeout_expired(struct work_struct *work)
>> {
>>    struct adv_info *adv_instance = container_of(work, struct adv_info,
>>                                                 timeout_exp.work);
>>    ...
>> }
>>
>> I couldn't find a way to get the list head of the adv info list entry so
>> that I could retrieve its containing hci_dev structure, though.
>>
>
> Once simple solution is to add a struct hci_dev pointer to struct
> adv_info. Once you get the pointer to the instance then you can obtain
> the hci_dev pointer that way.

Yes, that's an obvious solution albeit it's a bit ugly as it introduces 
extra redundancy. I thought of it, too, but I hoped I could avoid it. 
Maybe I can solve it like that for now and then we see whether another 
solution emerges once we got the refactored code in front of us.

Florian