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SubjectRe: [PATCH v3 1/3] usb: gadget: ccid: add support for USB CCID Gadget Device
Hi Greg,

On Wed, May 30, 2018 at 01:30:26PM +0200, Greg Kroah-Hartman wrote:
> On Wed, May 30, 2018 at 01:24:59PM +0200, Marcus Folkesson wrote:
> > Hi Andy,
> >
> > Thank you for your comments!
> > Many good catches here!
> >
> > On Wed, May 30, 2018 at 03:55:39AM +0300, Andy Shevchenko wrote:
> > > On Tue, May 29, 2018 at 9:50 PM, Marcus Folkesson
> > > <marcus.folkesson@gmail.com> wrote:
> > > > Chip Card Interface Device (CCID) protocol is a USB protocol that
> > > > allows a smartcard device to be connected to a computer via a card
> > > > reader using a standard USB interface, without the need for each manufacturer
> > > > of smartcards to provide its own reader or protocol.
> > > >
> > > > This gadget driver makes Linux show up as a CCID device to the host and let a
> > > > userspace daemon act as the smartcard.
> > > >
> > > > This is useful when the Linux gadget itself should act as a cryptographic
> > > > device or forward APDUs to an embedded smartcard device.
> > >
> > > > + * Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@gmail.com>
> > >
> > > > + *
> > >
> > > Redundant line
> > >
> >
> > Yep
> >
> > > > +static DEFINE_IDA(ccidg_ida);
> > >
> > > Where is it destroyed?
> >
> > Hm, I'm not sure it needs to be destroyed. From lib/idr.c:
> >
> > * You can also use ida_get_new_above() if you need an ID to be allocated
> > * above a particular number. ida_destroy() can be used to dispose of an
> > * IDA without needing to free the individual IDs in it. You can use
> > * ida_is_empty() to find out whether the IDA has any IDs currently allocated.
> >
> >
> > An empty ccidg_ida is the indication that we should clean up our
> > mess:
> >
> > static void ccidg_free_inst(struct usb_function_instance *f)
> > ...
> > if (ida_is_empty(&ccidg_ida))
> > ccidg_cleanup();
> >
> > If the IDA is empty, should I call ida_destroy() anyway?
> > Other similiar drivers does not seems to do that.
> >
> > I must say that I'm not very familiar with the IDA API.
>
> When your module is removed, you need to clean up any remaining memory
> that the ida used. It's not obvious at all, and is a pain as you would
> think that if you statically allocate one, like you have here, it would
> not be needed. You need to just call:
> ida_destroy(&ccidg_ida);
> in your module exit function.
>
> Hope this helps,

Thank you for making it clear.

Maybe I should use
#define DECLARE_USB_FUNCTION(_name, _inst_alloc, _func_alloc) \

instead of
#define DECLARE_USB_FUNCTION_INIT(_name, _inst_alloc, _func_alloc) \

and provide my own module_init/module_exit functions then?

Just give me a hint and I will do the same for
f_printer.c and
f_hid.c

as those use IDAs in a similiar way.

>
> greg k-h

Best regards,
Marcus Folkesson

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