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

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Message-ID: <878toh454w.fsf@linux.intel.com>
Date:   Tue, 07 Mar 2017 14:56:31 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Roger Quadros <rogerq@...com>, 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 Felipe,
>
> On Tuesday 07 Mar 2017 12:57:40 Felipe Balbi wrote:
>> Laurent Pinchart writes:
>> > 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.
>
> This is a userspace application patch. Feel free to send it to Greg, but I 
> don't think he will know what to do with it :-) Were you maybe confusing this 
> patch with the kernel fix that Roger sent a few days ago ? That one should be 
> queued, please keep it in your tree.

heh, my bad I got confused. I thought I was revieweing the kernel patch :-p

-- 
balbi

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