linux-kernel - Re: [RFC/RFT PATCH 0/6] Asynchronous UVC

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Date:   Tue, 5 Jun 2018 12:18:45 -0700
From:   Troy Kisky <troy.kisky@...ndarydevices.com>
To:     Kieran Bingham <kieran.bingham@...asonboard.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        laurent.pinchart@...asonboard.com
Cc:     Olivier BRAUN <olivier.braun@...reolabs.com>,
        Guennadi Liakhovetski <g.liakhovetski@....de>
Subject: Re: [RFC/RFT PATCH 0/6] Asynchronous UVC

On 6/5/2018 2:01 AM, Kieran Bingham wrote:
> Hi Troy
> 
> On 03/01/18 21:13, Troy Kisky wrote:
>> On 1/3/2018 12:32 PM, Kieran Bingham wrote:
>>> From: Kieran Bingham <kieran.bingham@...asonboard.com>
>>>
>>> The Linux UVC driver has long provided adequate performance capabilities for
>>> web-cams and low data rate video devices in Linux while resolutions were low.
>>>
>>> Modern USB cameras are now capable of high data rates thanks to USB3 with
>>> 1080p, and even 4k capture resolutions supported.
>>>
>>> Cameras such as the Stereolabs ZED or the Logitech Brio can generate more data
>>> than an embedded ARM core is able to process on a single core, resulting in
>>> frame loss.
>>>
>>> A large part of this performance impact is from the requirement to
>>> ‘memcpy’ frames out from URB packets to destination frames. This unfortunate
>>> requirement is due to the UVC protocol allowing a variable length header, and
>>> thus it is not possible to provide the target frame buffers directly.
>>
>>
>> I have a rather large patch that does provide frame buffers directly for bulk
>> cameras. It cannot be used with ISOC cameras.  But it is currently for 4.1.
>> I'll be porting it to 4.9 in a few days if you'd like to see it.
> 
> 
> How did you get on with this porting activity?
> 
> Is it possible to share any of this work with the mailing lists ?


This is pretty ugly all squashed together but here is the 4.9 patch

It does a bit more than 0 copy. I'll just post a link, because I doubt anyone
else wants to look.

https://github.com/boundarydevices/linux-imx6/commit/5cbb48a3332a6e8aad4a1359b1b5eb05eb0fff96

HTH
Troy

> 
> (If you have not ported to v4.9 - I think it would be useful even to post the
> v4.1 patch and we can look at what's needed for getting it ported to mainline)
> 
> --
> Regards
> 
> Kieran
> 
> 
>>
>> BR
>> Troy