linux-kernel - Re: [PATCH] uvc-gadget: Fix Set Interface (alternate setting) response behaviour

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Date:   Tue, 07 Mar 2017 12:57:40 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Roger Quadros <rogerq@...com>
Cc:     b-liu@...com, nsekhar@...com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uvc-gadget: Fix Set Interface (alternate setting) response behaviour


Hi,

Laurent Pinchart <laurent.pinchart@...asonboard.com> writes:
> Hi Roger,
>
> Thank you for the patch.
>
> On Friday 03 Mar 2017 13:17:15 Roger Quadros wrote:
>> On alternate setting change, webcam gadget sends us a UVC_EVENT_STREAMON
>> or UVC_EVENT_STREAMOFF event. It expects delayed status response on
>> STREAMON event only but doesn't expect us to send that response over USB.
>> It sends the delayed response when we issue the VIDIOC_STREAMON ioctl.
>>
>> So we must not send UVCIOC_SEND_RESPONSE ioctl in these cases that too
>> with invalid response length.
>
> The commit message only explains why we should not call UVCIOC_SEND_RESPONSE 
> in response to a STREAMON event, but not why we shouldn't either in response 
> to a STREAMOFF event. The patch is correct changing both, but I propose 
> wording the above two paragraphs as follows.
>
> "uvc-gadget: Do not send Set Interface (alternate setting) response twice
>
> On alternate setting change, the webcam gadget sends us a UVC_EVENT_STREAMON 
> or UVC_EVENT_STREAMOFF event. In the first case, the driver will issue a 
> delayed status response automatically when we call the VIDIOC_STREAMON ioctl. 
> In the second case, the driver sends the status response immediately. We must 
> thus not send the status response manually with UVCIOC_SEND_RESPONSE in any of 
> those cases."
>
> If you're fine with that I'll change the message when applying, there's no 
> need to resend the patch.

I have this in my testing/fixes and was planning to send it to Greg this
week. I can drop it from my queue, no problem, but then let me know as
you would need my acked-by.

-- 
balbi

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