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Subject: Re: [REGRESSION] usb: gadget: f_fs: Allow scatter-gather buffers
From:   Andrzej Pietrasiewicz <andrzej.p@collabora.com>
To:     John Stultz <john.stultz@linaro.org>
Cc:     Felipe Balbi <balbi@kernel.org>, "Yang, Fei" <fei.yang@intel.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Chen Yu <chenyu56@huawei.com>,
        lkml <linux-kernel@vger.kernel.org>,
        Linux USB List <linux-usb@vger.kernel.org>,
        Amit Pundir <amit.pundir@linaro.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        "kernel@collabora.com" <kernel@collabora.com>
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Date:   Mon, 20 May 2019 12:42:10 +0200
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Hi John,

<snip>

>> Is there anything else I can try for you?
> 
> Have you tried compiling FunctionFS with debugging enabled?
> You do so bu uncommenting:
> 
> /* #define DEBUG */
> /* #define VERBOSE_DEBUG */
> 
> at the beginning of drivers/usb/gadget/function/f_fs.c
> 
> Is there anything suspicious in the kernel log when you run it then?
> 


<snip>

> 
> One question that comes to my mind is this: Does the USB transmission
> stall (e.g. endpoint stall) or not? In other words, is adb connection
> broken because USB stops transmitting anything, or because the
> data is transmitted but its integrity is broken during transmission
> and that causes adb/adbd confusion which results in stopping their
> operation? Does anything keep happening on FunctionFS when adb
> connection is broken?

Any discoveries about the problem?

Andrzej