linux-kernel - Re: [PATCH v4] usb: gadget: f_fs: add "no

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Date:	Wed, 12 Nov 2014 20:44:14 -0600
From:	Felipe Balbi <balbi@...com>
To:	Felipe Balbi <balbi@...com>
CC:	Robert Baldyga <r.baldyga@...sung.com>,
	David Cohen <david.a.cohen@...ux.intel.com>,
	<gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <mina86@...a86.com>,
	<andrzej.p@...sung.com>, <m.szyprowski@...sung.com>,
	<k.opasiak@...sung.com>
Subject: Re: [PATCH v4] usb: gadget: f_fs: add "no_disconnect" mode

HI,

On Wed, Nov 05, 2014 at 01:43:21PM -0600, Felipe Balbi wrote:
> On Mon, Nov 03, 2014 at 10:11:02AM -0600, Felipe Balbi wrote:
> > Hi,
> > 
> > On Thu, Oct 09, 2014 at 03:21:51PM +0200, Robert Baldyga wrote:
> > > Since we can compose gadgets from many functions, there is the problem
> > > related to gadget breakage while FunctionFS daemon being closed. FFS
> > > function is userspace code so there is no way to know when it will close
> > > files (it doesn't matter what is the reason of this situation, it can
> > > be daemon logic, program breakage, process kill or any other). So when
> > > we have another function in gadget which, for example, sends some amount
> > > of data, does some software update or implements some real-time functionality,
> > > we may want to keep the gadget connected despite FFS function is no longer
> > > functional.
> > > 
> > > We can't just remove one of functions from gadget since it has been
> > > enumerated, so the only way to keep entire gadget working is to make
> > > broken FFS function deactivated but still visible to host. For this
> > > purpose this patch introduces "no_disconnect" mode. It can be enabled
> > > by setting mount option "no_disconnect=1", and results with defering
> > > function disconnect to the moment of reopen ep0 file or filesystem
> > > unmount. After closing all endpoint files, FunctionFS is set to state
> > > FFS_DEACTIVATED.
> > > 
> > > When ffs->state == FFS_DEACTIVATED:
> > > - function is still bound and visible to host,
> > > - setup requests are automatically stalled,
> > > - transfers on other endpoints are refused,
> > > - epfiles, except ep0, are deleted from the filesystem,
> > > - opening ep0 causes the function to be closes, and then FunctionFS
> > >   is ready for descriptors and string write,
> > > - unmounting of the FunctionFS instance causes the function to be closed.
> > > 
> > > Signed-off-by: Robert Baldyga <r.baldyga@...sung.com>
> > 
> > David, you have been messing with ffs lately, can I get a Tested-by from
> > you on this patch ?
> 
> ping. David ? Any chance you can test this one out ?

a reminder on this request, it's getting close to tree lockdown
(probably another 2 to 3 weeks).

-- 
balbi

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