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

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

Alan Stern wrote:
> On Mon, 20 Apr 2009, Rafael J. Wysocki wrote:
>
>   
>> On Thursday 16 April 2009, Michael Trimarchi wrote:
>>     
>>> Drivers on embedded systems would be smart enough
>>> to know that some of the devices should remain powered up, because
>>> they could still be useful even when the CPU wasn't running.
>>> The patch add the in_use attribute, that it can be used by the
>>> the drivers to avoid power down during suspend.
>>>       
>> OK, so the idea is that in_use will be set by the user space for devices that
>> shouldn't be suspended.  Is this correct?
>>
>> Assuming it is, I'd call the flag 'in_use' rather than 'is_inuse'.  Also, if
>> may_inuse is supposed to mean that we can set in_use for this device, I'd call
>> it 'in_use_valid', I'd make it be unset by default and I'd allow the driver to
>> unset it if it is going to react to 'in_use'.
>>     
>
> I don't see why two separate flags are needed.  Why can't there be just 
> one?
>
> Also, I don't see why the in_use flag has to propagate down to all the 
> descendant devices when it is set.  Why not let userspace be 
> responsible for that?
>   
Yes it is possible to leave the possibility to the userspace. With this 
patch
the userspace can deselect/select a tree in one write and eventually 
reanable subpart. This
was the old design choice to use kernel to track dependences.
> Finally, I don't like either name very much.  This flag is supposed to
> indicate that the device is being used in a mode that can run by itself
> even when the rest of the system is suspended.  Calling it "in_use" 
> doesn't express the crucial fact that the device is self-sufficient.
>   
Ok I will change
> Alan Stern
>
>
>   
Michael