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From: Elvinas <elvinas@veikia.lt>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-usb@vger.kernel.org
Subject: Request for information how to disable USB bulk endpoint transfer validation
Date: Tue, 24 Apr 2018 20:41:12 +0300	[thread overview]
Message-ID: <32f6b728-b743-45c0-ebc6-a3fc71dd1be0@veikia.lt> (raw)

Hello,

On 04/23/2018 11:50 PM, Alan Stern wrote:
>>
>> In ZWO forums there was a suggestion to revert USB packet validation by applying a "break"
>> to Linux kernel. With some changes to line locations I have applied the patch below and
>> camera started to work on a desktop with USB 2.0 host.
> 
> The patch you wrote isn't ideal; the one below is better.  In fact, the
> code should be like this already.  It was an oversight.
Well, that was not my patch. I have just updated line numbers.

>> Question: can anyone point what lines should be commented out to ignore packet sizes for
>> USB 2.0 device, when attached to USB 3.0 host?
> 
> As far as I know, there is no way to do this.  USB-3 xHCI host
> controllers validate maxpacket sizes in the hardware, not in software,
> and there isn't any way to change the hardware's behavior.  But I am
> not an expert on xHCI.
> 
> Does the camera work when attached to a USB-3 host controller on a
> computer running Windows or Mac OS X?

It looks you are right. Camera does not work properly on a Windows computer with USB 3.0 
host. So it may be as you said - data is validated by hardware, device does not work and I 
will have thrown some money out.

Anyway thanks for the help

             reply	other threads:[~2018-04-24 17:41 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-24 17:41 Elvinas [this message]
  -- strict thread matches above, loose matches on Subject: below --
2018-04-23 20:50 Request for information how to disable USB bulk endpoint transfer validation Alan Stern
2018-04-23 19:50 Elvinas

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