linux-kernel - Re: [PATCH v5 01/46] usb: gadget: encapsulate endpoint claiming mechanism

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Date:	Thu, 20 Aug 2015 19:16:48 +0200
From:	Robert Baldyga <r.baldyga@...kerion.com>
To:	balbi@...com
CC:	Robert Baldyga <r.baldyga@...sung.com>, gregkh@...uxfoundation.org,
	Peter.Chen@...escale.com, johnyoun@...opsys.com,
	dahlmann.thomas@...or.de, nicolas.ferre@...el.com,
	cernekee@...il.com, leoli@...escale.com, daniel@...que.org,
	haojian.zhuang@...il.com, robert.jarzmik@...e.fr,
	michal.simek@...inx.com, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-geode@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, andrzej.p@...sung.com,
	m.szyprowski@...sung.com, stern@...land.harvard.edu,
	petr.cvek@....cz
Subject: Re: [PATCH v5 01/46] usb: gadget: encapsulate endpoint claiming mechanism

On 08/20/2015 06:48 PM, Felipe Balbi wrote:
> On Thu, Aug 20, 2015 at 06:28:14PM +0200, Robert Baldyga wrote:
>> Hi Felipe,
>>
>> On 08/20/2015 05:35 PM, Felipe Balbi wrote:
>> [...]
>>> just letting you know that this regresses all gadget drivers making them
>>> try to disable previously disabled endpoints and enable previously
>>> enabled endpoints.
>>>
>>> I have a possible fix (see below) but then it shows a problem on the
>>> host side when using with g_zero (see further below):
>>>
>>> commit 3b8932100aacb6cfbffe288ca93025d8b8430c00
>>> Author: Felipe Balbi <balbi@...com>
>>> Date:   Wed Aug 19 18:05:27 2015 -0500
>>>
>>>      usb: gadget: fix ep->claimed lifetime
>>>
>>>      In order to fix a regression introduced by commit
>>>      cc476b42a39d ("usb: gadget: encapsulate endpoint
>>>      claiming mechanism") we have to introduce a simple
>>>      helper to check if a particular is enabled or not.
>>>
>>>      After that, we need to move ep->claimed lifetime to
>>>      usb_ep_enable() and usb_ep_disable() since those
>>>      are the only functions which actually enable and
>>>      disable endpoints.
>>>
>>>      A follow-up patch will come to drop all driver_data
>>>      checks from function drivers, since those are, now,
>>>      pointless.
>>>
>>>      Fixes: cc476b42a39d ("usb: gadget: encapsulate endpoint
>>>      	claiming mechanism")
>>>      Cc: Robert Baldyga <r.baldyga@...sung.com>
>>>      Signed-off-by: Felipe Balbi <balbi@...com>
>>>
>>> diff --git a/drivers/usb/gadget/epautoconf.c b/drivers/usb/gadget/epautoconf.c
>>> index 978435a51038..ad45070cd76f 100644
>>> --- a/drivers/usb/gadget/epautoconf.c
>>> +++ b/drivers/usb/gadget/epautoconf.c
>>> @@ -126,7 +126,6 @@ found_ep:
>>>   	ep->address = desc->bEndpointAddress;
>>>   	ep->desc = NULL;
>>>   	ep->comp_desc = NULL;
>>> -	ep->claimed = true;
>>
>> Removing this line causes autoconfig can return the same endpoint many
>> times. This probably causes problems with g_zero.
>>
>> I will try to fix it ASAP.
>
> I was considering the same thing, but the lifetime of ->claimed doesn't
> look correct to me either way. Note that once the flag is enabled, it
> won't get disabled by most gadget drivers.

And it should not be. This flag is indicator, that endpoint is used by 
some function. It should be set once by usb_ep_autoconfig() and cleared 
by usb_ep_autoconfig_reset().

I wonder what is reason of this enable/disable regression. Maybe the 
problem is that we don't set ep->driver_data to NULL in 
usb_ep_autoconfig_reset() (so far it was done). Does this problem occur 
while gadget is binded to UDC for the first time, or at any next time? 
Unfortunately at this moment I don't have access to my hardware, so it 
will take a moment before I will setup some testing environment.

Thanks,
Robert

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