linux-kernel - Re: [PATCHv2 2/2] check quirk to pad epout buf size when not aligned to maxpacketsize

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Message-ID: <5282724F.10207@linux.intel.com>
Date:	Tue, 12 Nov 2013 10:24:15 -0800
From:	David Cohen <david.a.cohen@...ux.intel.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Michal Nazarewicz <mina86@...a86.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 2/2] check quirk to pad epout buf size when not aligned
 to maxpacketsize

>>>> IIUC, req->length should still be set to len, not to data_len.
>>
>> I misunderstood the first time I read it:
>> In order to avoid DWC3 to stall, we need to update req->length (this is
>> the most important fix). kmalloc() is updated too to prevent USB
>> controller to overflow buffer boundaries.
> 
> Here I disagree.
> 
> If the DWC3 hardware stalls, it is up to the DWC3 UDC driver to fix it.  
> Gadget drivers should not have to worry.  Most especially, gadget 
> drivers should not lie about a request length.
> 
> If the UDC driver decides to round up req->length before sending it to
> the hardware, that's okay.  But req->length should be set to len, not
> data_len.  And if the hardware receives more than len bytes of data,
> the UDC driver should set req->status to -EOVERFLOW.

Got your point. As long as buffer allocation has enough size, DWC3 is
able to fix itself. I'm fine with this approach too. But in this case I
will need to redo my DWC3 patch and my validation.

Br, David

> 
> Alan Stern
> 

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