linux-kernel - Re: [PATCH] usb: gadget: f

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Message-ID: <20141007022851.GA13956@saruman>
Date:	Mon, 6 Oct 2014 21:28:51 -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>,
	<mina86@...a86.com>, <andrzej.p@...sung.com>,
	<k.opasiak@...sung.com>
Subject: Re: [PATCH] usb: gadget: f_fs: add "zombie" mode

Hi,

On Mon, Oct 06, 2014 at 01:25:14PM +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. In some
> cases it's strongly desired to keep gadget alive for a while, despite
> FunctionFS files are closed, to allow another functions to complete
> some presumably critical operations.
> 
> For this purpose this patch introduces "zombie" mode. It can be enabled
> by setting mount option "zombie=1", and results with defering function
> closure to the moment of reopening ep0 file or filesystem umount.
> 
> When ffs->state == FFS_ZOMBIE:
> - function is still binded and visible to host,
> - setup requests are automatically stalled,
> - all another transfers are refused,
> - opening ep0 causes function close, and then FunctionFS is ready for
>   descriptors and string write,
> - umount of functionfs cause function close.
> 
> Signed-off-by: Robert Baldyga <r.baldyga@...sung.com>

Can you further explain how do you trigger this ? Do I understand
correctly that you composed a gadget using configfs and that gadget has
functionfs + another gadget ?

Then what do you need to do the trigger the issue, and what really _is_
the issue ? Is gadget disconnecting from host too early ? Do you see a
crash ? Memory leak ? Any logs available ? Any steps to reproduce ?

Quite frankly, I don't really like this "zombie" mode. <joke> I know
there's a "The Walking Dead" hype right now, but this is too much.
</joke>

Anyway, please giver me further details of how to get this done.

-- 
balbi

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