MIME-Version: 1.0
In-Reply-To: <CAAeHK+ytJCrnJhN8ck0iwbOi=mNzrx150vYxp3GhCmk0Wvi0dA@mail.gmail.com>
References: <CAAeHK+ytJCrnJhN8ck0iwbOi=mNzrx150vYxp3GhCmk0Wvi0dA@mail.gmail.com>
From: Tal Shorer <tal.shorer@gmail.com>
Date: Tue, 13 Jun 2017 19:02:10 +0300
Message-ID: <CAFDyS3P3S9U_KhMBLvS1GanzprY09rsuDbstB8B7-vaASwVKzA@mail.gmail.com>
Subject: Re: gadgetfs: how to wait for USB device initialization?
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Elena Reshetova <elena.reshetova@intel.com>,
        USB list <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller <syzkaller@googlegroups.com>,
        Dmitry Vyukov <dvyukov@google.com>, Kostya Serebryany <kcc@google.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 926
Lines: 25

On Tue, Jun 13, 2017 at 3:21 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> Hi!
>
> I'm trying to use gadgetfs to fuzz USB device drivers by simply
> connecting random devices for now.
>
> What I want to achieve right now is the following:
>
> 1. mount gadgetfs
> 2. emulate connection of a new USB device
> 3. wait for the device to finish initializing
> 4. unmount gadgetfs
> 5. goto 1
>
> The question is how do I wait for the device to finish initializing
> (the corresponding USB driver to finish probing?) before unmounting
> gadgetfs? As I understand, when I write device description to
> "/dev/gadget/dummy_udc" the initialization happens asynchronously
> after writing is done.
>

You can use inotify on the state file inside a udc's sysfs directory.
It's awesome like that.
Here's a sample code that doesn't do any cleanups because I'm lazy:
https://gist.github.com/talshorer/61be1bc3472cc2a7b4866b9bd5a239ca