linux-kernel - Re: [PATCH 1/1] media: uvcvideo: Increase UVC_CTRL_CONTROL

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Message-ID: <CADvTj4pY+2OXPLy1_pVuiA6=BR9u8634HhP5XBWnGUTVPk5wtg@mail.gmail.com>
Date:   Mon, 15 Nov 2021 06:16:50 -0700
From:   James Hilliard <james.hilliard1@...il.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ricardo Ribalda <ribalda@...omium.org>
Subject: Re: [PATCH 1/1] media: uvcvideo: Increase UVC_CTRL_CONTROL_TIMEOUT to
 5 seconds.

On Mon, Nov 15, 2021 at 2:30 AM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi James,
>
> Thank you for the patch.
>
> On Sun, Nov 14, 2021 at 01:52:36AM -0700, James Hilliard wrote:
> > Some uvc devices appear to require the maximum allowed USB timeout
> > for GET_CUR/SET_CUR requests.
>
> Could you list the devices that you know about which require this change
> ?

Seems random unbranded chinese made cameras is where I was hitting it,
but I was seeing a decent amount of others encountering similar timeout issues
when researching the issue.

>
> > So lets just bump the UVC control timeout to 5 seconds which is the
> > same as the usb ctrl get/set defaults:
> > USB_CTRL_GET_TIMEOUT 5000
> > USB_CTRL_SET_TIMEOUT 5000
>
> The USB specification (section 9.2.6.4) requires the device to send the
> first data packet within 500ms of reception of the request. A 500ms
> timeout may thus be a bit too short for compliant devices, but 5000ms
> seems to be a very large margin. I'm wondering if it would make sense to
> go for a lower value.

The 500 ms timeout appears to be applicable:
"For standard device requests that require data stage transfer to the host"

While the 5s timeout appears to be applicable to:
"For standard device requests that require a data stage transfer to the device"

>From what I could tell a lot of software just uses the 5s timeout everywhere for
these GET_CUR and SET_CUR requests, I think it's probably best to just use
the 5s timeout, that way it's much less likely that we'll see timeout
bugs here as
it seems likely a lot of vendors are testing against software using
the 5s timeout.

I don't really see any harm in bumping it up to 5 seconds, maybe there
is something
I'm missing there though?

>
> > Fixes:
> > Failed to query (GET_CUR) UVC control 11 on unit 2: -110 (exp. 1).
> > Failed to query (SET_CUR) UVC control 3 on unit 2: -110 (exp. 2).
> >
> > Signed-off-by: James Hilliard <james.hilliard1@...il.com>
> > ---
> >  drivers/media/usb/uvc/uvcvideo.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index fd4f5ef47dfb..583c51ac3eec 100644
> > --- a/drivers/media/usb/uvc/uvcvideo.h
> > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > @@ -189,7 +189,7 @@
> >  /* Maximum status buffer size in bytes of interrupt URB. */
> >  #define UVC_MAX_STATUS_SIZE  16
> >
> > -#define UVC_CTRL_CONTROL_TIMEOUT     500
> > +#define UVC_CTRL_CONTROL_TIMEOUT     5000
> >  #define UVC_CTRL_STREAMING_TIMEOUT   5000
> >
> >  /* Maximum allowed number of control mappings per device */
>
> --
> Regards,
>
> Laurent Pinchart