From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754023AbaGHX2j (ORCPT ); Tue, 8 Jul 2014 19:28:39 -0400 Received: from mail-ve0-f175.google.com ([209.85.128.175]:37429 "EHLO mail-ve0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751344AbaGHX2h (ORCPT ); Tue, 8 Jul 2014 19:28:37 -0400 MIME-Version: 1.0 In-Reply-To: <8119752.rPOQIYa4Af@avalon> References: <539FDC4F.4030000@redhat.com> <1403016348-10129-1-git-send-email-vpalatin@chromium.org> <8119752.rPOQIYa4Af@avalon> From: Vincent Palatin Date: Tue, 8 Jul 2014 16:28:16 -0700 X-Google-Sender-Auth: t3vHMRYxq2QJTE-NlRDSDdUo3u4 Message-ID: Subject: Re: [PATCH v2] V4L: uvcvideo: Add support for relative pan/tilt controls To: Laurent Pinchart Cc: Pawel Osciak , Hans de Goede , "linux-media@vger.kernel.org" , LKML , Olof Johansson , Zach Kuznia , Mauro Carvalho Chehab Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 25, 2014 at 2:54 AM, Laurent Pinchart wrote: > 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. Ok, I will add another patch to create new V4L2_CID_PAN_SPEED / V4L2_CID_TILT_SPEED controls. -- Vincent