Re: [RFC Add in_use attribute] Let the driver know if it's in use

[Michael Trimarchi <trimarchi@gandalf.sssup.it>]

Hi,

Rafael J. Wysocki wrote:
> On Thursday 23 April 2009, Michael Trimarchi wrote:
>   
>> Greg KH wrote:
>>     
>>> On Tue, Apr 21, 2009 at 08:43:28AM +0200, Michael Trimarchi wrote:
>>>   
>>>       
>>>>>>> Exactly, what are you trying to do that differs from
>>>>>>> device_for_each_child()?
>>>>>>>   
>>>>>>>       
>>>>>>>           
>>>>>>>               
>>>>>> Is device for each child use to visist the first level of the tree?
>>>>>>     
>>>>>>         
>>>>>>             
>>>>> Have you tried it?
>>>>>   
>>>>>       
>>>>>           
>>>> No, I take a look at the code.
>>>>
>>>> int device_for_each_child(struct device *parent, void *data,
>>>>                           int (*fn)(struct device *dev, void *data))
>>>> {
>>>>         struct klist_iter i;
>>>>         struct device *child;
>>>>         int error = 0;
>>>>
>>>>         klist_iter_init(&parent->p->klist_children, &i);
>>>>
>>>> I was thinking that the klist_children is the fist_level one children, 
>>>> so each time
>>>> a device is registerd it add the link to the parent.
>>>>     
>>>>         
>>> Yes it does.
>>>
>>> But you have to start at some device, right?  So you don't need to
>>> iterate over it, just go from there on down if needed.
>>>   
>>>       
>> I start for a device, go down until I find a leaf or find that the 
>> subtree is marked.
>> Mark the leaf and go up and take the next node like the walk_tg_tree. 
>> The difference is
>> that I skip subtree if they are mark in_use.
>>     
>>> So I don't see why this helper function is needed at all yet, shouldn't
>>> we be doing the check within the normal suspend device walk of the tree?
>>>   
>>>       
>> Sorry but here I need some help here. Where is the walk of the device 
>> tree during suspend?
>>     
>
>   

> In drivers/base/power/main.c there are functions like dpm_suspend(), for one
> example, that walk the device tree, but they do it in a simplified way, using a
> list prepared specifically for this purpose (so the walk is in fact linear).
>   
I don't want add a new list and
If I use the dpm_list a must go back to the root for each element using 
the parent and check
the flag because the list maybe don't mantein the parent relation.

example:
s(A) is son of A ss(A) etc

A-B-s(B)-s(B)-s(A)-ss(B)-ss(A)

I don't know if B the second element has child of B I must look it's 
parent and so on.
So the complexty increase.

The suspend order is correct but the computation time is worse. Maybe I 
can move
the code outside the base/core.c and put it in the power/main.c but I 
don't have
the next_device function and other to move up and down. I put there that 
function
because I have all the necessary code.

Michael

> Thanks,
> Rafael
>
>