linux-kernel - Re: [PACTH v1] cdc-wdm: Clear read pipeline in case of error

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Date:	Tue, 2 Aug 2016 09:54:04 -0400
From:	Robert Foss <robert.foss@...labora.com>
To:	Oliver Neukum <oneukum@...e.com>
Cc:	pprabhu@...omium.org, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PACTH v1] cdc-wdm: Clear read pipeline in case of error



On 2016-08-02 08:23 AM, Oliver Neukum wrote:
> On Thu, 2016-07-28 at 14:19 -0400, robert.foss@...labora.com wrote:
>> From: Prathmesh Prabhu <pprabhu@...omium.org>
>>
>> Implemented queued response handling. This queue is processed every
>> time the
>> WDM_READ flag is cleared.
>>
>> In case of a read error, userspace may not actually read the data,
>> since the
>> driver returns an error through wdm_poll. After this, the underlying
>> device may
>> attempt to send us more data, but the queue is not processed. While
>> userspace is
>> also blocked, because the read error is never cleared.
>
> Could you explain why user space cannot just read more data?
> That will clear the error.

Userspace certainly could read more data, but for the case when 
userspace doesn't read and clear a potential an error, we still would 
like to not be stuck if the device sends more data.

I hope that answers your question, if not I'll try to be more elaborate.

>
> 	Regards
> 		Oliver
>
>