From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756839AbbBQOl4 (ORCPT ); Tue, 17 Feb 2015 09:41:56 -0500 Received: from mail-lb0-f169.google.com ([209.85.217.169]:44416 "EHLO mail-lb0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752788AbbBQOlh (ORCPT ); Tue, 17 Feb 2015 09:41:37 -0500 From: Ricardo Ribalda Delgado To: Hans Verkuil , Mauro Carvalho Chehab , Jonathan Corbet , Arun Kumar K , Sylwester Nawrocki , Sakari Ailus , Antti Palosaari , linux-media@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Ricardo Ribalda Delgado Subject: [PATCH 2/2] media/Documentation: Volatile writable Date: Tue, 17 Feb 2015 15:41:30 +0100 Message-Id: <1424184090-14945-2-git-send-email-ricardo.ribalda@gmail.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1424184090-14945-1-git-send-email-ricardo.ribalda@gmail.com> References: <1424184090-14945-1-git-send-email-ricardo.ribalda@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Volatile variables are also writable now. Update the documentation accordingly. Signed-off-by: Ricardo Ribalda Delgado --- Documentation/DocBook/media/v4l/vidioc-dqevent.xml | 7 ++++--- Documentation/DocBook/media/v4l/vidioc-queryctrl.xml | 6 ++++-- Documentation/video4linux/v4l2-controls.txt | 4 +++- 3 files changed, 11 insertions(+), 6 deletions(-) diff --git a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml index b036f89..38d907e 100644 --- a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml +++ b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml @@ -318,9 +318,10 @@ V4L2_EVENT_CTRL_CH_VALUE 0x0001 This control event was triggered because the value of the control - changed. Special case: if a button control is pressed, then this - event is sent as well, even though there is not explicit value - associated with a button control. + changed. Special cases: Volatile controls do no generate this event; + If a button control is pressed, then this event is sent as well, + even though there is not explicit value associated with a button + control. V4L2_EVENT_CTRL_CH_FLAGS diff --git a/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml b/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml index 2bd98fd..6e1e98d 100644 --- a/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml +++ b/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml @@ -599,8 +599,10 @@ writing a value will cause the device to carry out a given action This control is volatile, which means that the value of the control changes continuously. A typical example would be the current gain value if the device is in auto-gain mode. In such a case the hardware calculates the gain value based on -the lighting conditions which can change over time. Note that setting a new value for -a volatile control will have no effect. The new value will just be ignored. +the lighting conditions which can change over time. Another example would be an error +flag (missed trigger, invalid voltage on the sensor). In those situations the user +could write to the control to acknowledge the error, but that write will never +generate a V4L2_EVENT_CTRL_CH_VALUE event. V4L2_CTRL_FLAG_HAS_PAYLOAD diff --git a/Documentation/video4linux/v4l2-controls.txt b/Documentation/video4linux/v4l2-controls.txt index 0f84ce8..5517db6 100644 --- a/Documentation/video4linux/v4l2-controls.txt +++ b/Documentation/video4linux/v4l2-controls.txt @@ -344,7 +344,9 @@ implement g_volatile_ctrl like this: } Note that you use the 'new value' union as well in g_volatile_ctrl. In general -controls that need to implement g_volatile_ctrl are read-only controls. +controls that need to implement g_volatile_ctrl are read-only controls. If they +are not, a V4L2_EVENT_CTRL_CH_VALUE will not be generated when the control +changes. To mark a control as volatile you have to set V4L2_CTRL_FLAG_VOLATILE: -- 2.1.4