On Tue, Jun 07, 2016 at 11:59:57AM +0200, Krzysztof Opasiak wrote: > Hi, > > On Tue, Jun 7, 2016 at 11:06 AM, Peter Chen <peter.chen@xxxxxxx> wrote: > > > > > >>-----Original Message----- > >>From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] > >>On Behalf Of Krzysztof Opasiak > >>Sent: Tuesday, June 07, 2016 3:46 PM > >>To: Peter Chen <hzpeterchen@xxxxxxxxx> > >>Cc: Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx>; balbi@xxxxxxxxxx; Greg Kroah- > >>Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Andrzej Pietrasiewicz > >><andrzej.p@xxxxxxxxxxx>; Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>; > >>linux-usb@xxxxxxxxxxxxxxx > >>Subject: Re: [RFC][PATCH] usb: gadget: Allow to build both USB functions and > >>legacy gadgets > >> > >>Hi, > >> > >>On Tue, Jun 7, 2016 at 3:27 AM, Peter Chen <hzpeterchen@xxxxxxxxx> wrote: > >>> On Mon, Jun 06, 2016 at 09:40:33PM +0200, Krzysztof Opasiak wrote: > >>>> Currently it is possible to build in some subset of usb functions > >>>> *OR* some gadget module. This is limited only by Kconfig not any > >>>> functionality. > >>>> > >>>> This patch removes this limitation. With this patch it is possible to > >>>> set up all build combinations: > >>>> 1) Multiple gadgets build in > >>> > >>> If that, what the user will expect if choosing multiple gadgets? > >>> Eg, if he chooses g_ncm and g_mass_storage, will he expect his udc has > >>> both mass_storage and ncm function, but it is not the fact, only the > >>> first gadget function will work. > >>> > >> > >>Not exactly one. You may build in multiple modules and use those multiple modules if > >>you have multiple udcs. > >> > > > > My concern is: with your patch, the user may get unexpected results if he builds in > > multiple gadgets for this single udc. At current code, the user can't do that, then he will > > not get unexpected results. How do you consider that? > > > > That's true but even without this patch user may build multiple > gadgets as a modules. > > Even more, after commit (855ed04 "usb: gadget: udc-core: independent > registration of > gadgets and gadget drivers") it is possible to load multiple gadget > modules even if we have one UDC. > > So why would you like to disallow building in multiple gadgets if user > can build them as a modules and simply load? For module, the user can control which one to load, he or she can choose which function he needs. But if they are build-in, the user may make mistake and choose multiple gadgets, and get the unexpected results. This is only I concern. I just do not see the benefits that allow building in multiple gadgets, If you have some use cases, then that's reason for doing that:) > > If you concern about order of probing and binding to udc, I think that > we can add udc module param to all legacy gadgets so user can specify > in kernel cmd line where each gadget should be bound. > Yes, currently, we can't do that even the gadget is module, but the change may not be small. Now, we have configfs, it is not so necessary to add this future. -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
