linux-kernel - Re: [PATCH] usb: gadget: add claimed field in struct usb

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Message-ID: <20140630183337.GS31442@saruman.home>
Date:	Mon, 30 Jun 2014 13:33:37 -0500
From:	Felipe Balbi <balbi@...com>
To:	Robert Baldyga <r.baldyga@...sung.com>
CC:	<balbi@...com>, <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<m.szyprowski@...sung.com>, <andrzej.p@...sung.com>
Subject: Re: [PATCH] usb: gadget: add claimed field in struct usb_ep

On Tue, Jun 24, 2014 at 02:16:35PM +0200, Robert Baldyga wrote:
> On 06/23/2014 08:27 PM, Felipe Balbi wrote:
> > Hi,
> > 
> > On Mon, Jun 23, 2014 at 08:07:43AM +0200, Robert Baldyga wrote:
> >> On 06/19/2014 05:08 PM, Felipe Balbi wrote:
> >>> On Mon, Jun 16, 2014 at 10:20:36AM +0200, Robert Baldyga wrote:
> >>>> This field allows to mark ep as claimed in more clear way. Claiming
> >>>> endpoint by setting driver_data to non-null value is leaky solution
> >>>> and makes code unreadable.
> >>>
> >>> how come ? How can it be unreadable ? how can it be leaky ?
> >>>
> >>
> >> What if gadget will not assign any value to driver_data (just like
> >> Gadget Zero do)? Endpoint will be seen as not used, and autoconfig will
> > 
> > huh ??? The gadget isn't the endpoint user, the function is. Look at
> > f_sourcesink.c and f_loopback.c. If the function doesn't set anything to
> > driver_data, then that's a bug on the function which needs fixing.
> > 
> > Moreover, if there's a function which doesn't set driver_data, we could
> > just as well have a function which doesn't set "claimed", so the problem
> > is the same.
> > 
> 
> I mean the function, not the gadget. Sorry for confusion.
> Mechanism I developed marks endpoint as claimed *inside autoconfig
> function*. It's significant difference, because there's not possible to
> forget to mark that endpoint is claimed. When endpoint is returned from
> autoconfig function, it belongs to function, and the function doesn't
> need to do anything to claim obtained endpoint - it's already done.

we still might need to keep driver_data though. Some functions might
need it. But now that you explained your goal, I can see how that might
help. Please send a complete patchset also with the implementation for
ep_autoconfig so we can all review your idea.

cheers

-- 
balbi

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