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

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Date:	Thu, 20 Aug 2015 12:44:09 -0500
From:	Felipe Balbi <balbi@...com>
To:	Robert Baldyga <r.baldyga@...kerion.com>
CC:	<balbi@...com>, 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

Hi,

On Thu, Aug 20, 2015 at 07:16:48PM +0200, Robert Baldyga wrote:
> 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().

have you considered switching interfaces and/or alternate settings ?

> 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.

yeah, that's okay. We've got time.

-- 
balbi

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