Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755788AbaFYJxn (ORCPT ); Wed, 25 Jun 2014 05:53:43 -0400 Received: from perceval.ideasonboard.com ([95.142.166.194]:56931 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750851AbaFYJxl (ORCPT ); Wed, 25 Jun 2014 05:53:41 -0400 From: Laurent Pinchart To: Pawel Osciak Cc: Vincent Palatin , Hans de Goede , "linux-media@vger.kernel.org" , linux-kernel@vger.kernel.org, Olof Johansson , Zach Kuznia , Mauro Carvalho Chehab Subject: Re: [PATCH v2] V4L: uvcvideo: Add support for relative pan/tilt controls Date: Wed, 25 Jun 2014 11:54:30 +0200 Message-ID: <8119752.rPOQIYa4Af@avalon> User-Agent: KMail/4.11.5 (Linux/3.12.21-gentoo-r1; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <539FDC4F.4030000@redhat.com> <1403016348-10129-1-git-send-email-vpalatin@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Pawel, On Wednesday 25 June 2014 11:46:24 Pawel Osciak wrote: > On Tue, Jun 17, 2014 at 11:45 PM, Vincent Palatin wrote: > > Map V4L2_CID_TILT_RELATIVE and V4L2_CID_PAN_RELATIVE to the standard UVC > > CT_PANTILT_RELATIVE_CONTROL terminal control request. > > > > Tested by plugging a Logitech ConferenceCam C3000e USB camera > > and controlling pan/tilt from the userspace using the VIDIOC_S_CTRL ioctl. > > Verified that it can pan and tilt at the same time in both directions. > > > > Signed-off-by: Vincent Palatin > > > > Change-Id: I7b70b228e5c0126683f5f0be34ffd2807f5783dc > > --- > > > > Changes > > v2: fix control request name in description. > > The patch looks good, but I have a more general comment for everyone to > consider. This doesn't match the expected functionality of > controls V4L2_CID_PAN/TILT_RELATIVE. This is basically an on/off switch for > pan/tilt, which once enabled will keep going until turned off (or I'm > guessing until the maximum pan/tilt is reached), while the controls are > supposed to expose an ability to turn the camera by a specified amount. > Here the amount will also be ignored... I agree with you here, and this mismatch between the V4L and UVC controls is the reason why I haven't implemented relative pan/tilt support. > Given that this is a standard UVC control, perhaps we need new V4L2 > controls for it, as I'm assuming we can't change the meaning of existing > controls? We could extend the meaning of the controls to cover the UVC behaviour in a device-specific fashion, but that would be confusing for applications, so new controls might be a better idea. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/