On 27 June 2011 15:44, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> * Jassi Brar | 2011-06-25 01:34:11 [+0530]:
>
>> Currently there is no way for a gadget driver to save pointer to resources
>>(which may be common to more than one function) that it allocates during
>> config bind.
>>
>> Even single-function configurations have to free such data in function's
>>unbind callback. Which isn't very correct, because we have a situation where
>>call to a structure's member callback frees the space occupied by parent
>>structure.
>
> Is it causing any harm somewhere? If so could you describe it / post an
> example?
>
No harm yet. But it is the right way to go, IMHO.
As I said, freeing resources in function-unbind that were allocated in
config-bind isn't very neat.
Ok, let me dig deeper...
The definition of 'struct usb_function' specifies
@unbind: Reverses @bind; called as a side effect of unregistering the
driver which added this function.
whereas currently it also un-does the config-bind - though it's not a
problem because
it is usually a simple matter of kfree(gadget_structure)
b)
Say if a configuration needs to have more than one function(composite
device) that share
a common resource. We don't have a place to free such a resource as
the current situation is.
That is without saving local static pointers during config-bind.
I admit this scenario is a bit futuristic, but so is preparing for
need to have multiple UDC drivers
compiled in single kernel image :)
>> Patch-1 adds a new hook to 'struct usb_configuration'
>> Patch-2,3 converts Zero and Webcam gadget drivers for a start.
>>
>> Other gadgets could be converted(though not necessary) as and when
>>interest arise.
>
> It would be nice to have consistent behaviour across a subsystem.
Of course, I just wasn't sure if nobody would suggest 'Why bother if all is ok?'
So I converted only two drivers as examples atm.
Thanks,
Jassi
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