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

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Message-ID: <YZIorH8D7NPB3w5B@pendragon.ideasonboard.com>
Date:   Mon, 15 Nov 2021 11:30:20 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     James Hilliard <james.hilliard1@...il.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, 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.

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
?

> 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.

> 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