From patchwork Mon Nov 21 18:15:15 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jacopo Mondi X-Patchwork-Id: 87690 Received: from vger.kernel.org ([23.128.96.18]) by www.linuxtv.org with esmtp (Exim 4.92) (envelope-from ) id 1oxBKZ-006jMS-BS; Mon, 21 Nov 2022 18:15:43 +0000 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229628AbiKUSPk (ORCPT + 1 other); Mon, 21 Nov 2022 13:15:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229702AbiKUSPj (ORCPT ); Mon, 21 Nov 2022 13:15:39 -0500 Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6399AC0528 for ; Mon, 21 Nov 2022 10:15:38 -0800 (PST) Received: (Authenticated sender: jacopo@jmondi.org) by mail.gandi.net (Postfix) with ESMTPSA id B1F6BC0005; Mon, 21 Nov 2022 18:15:35 +0000 (UTC) From: Jacopo Mondi To: Sakari Ailus , Laurent Pinchart , Dave Stevenson , Hans Verkuil , Mauro Carvalho Chehab Cc: Jacopo Mondi , Linux Media Mailing List Subject: [PATCH v2 2/2] documentation: media: camera_sensor: Update exposure on blanking change Date: Mon, 21 Nov 2022 19:15:15 +0100 Message-Id: <20221121181515.34008-3-jacopo@jmondi.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221121181515.34008-1-jacopo@jmondi.org> References: <20221121181515.34008-1-jacopo@jmondi.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,WEIRD_QUOTING autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-LSpam-Score: -2.4 (--) X-LSpam-Report: No, score=-2.4 required=5.0 tests=BAYES_00=-1.9,HEADER_FROM_DIFFERENT_DOMAINS=0.5,MAILING_LIST_MULTI=-1,WEIRD_QUOTING=0.001 autolearn=ham autolearn_force=no The maximum achieable exposure time in a camera sensor is usually bound by the total frame height (visible + blankings) minus a fixed sensor-speific offset. When the vertical blanking control value is changed, the exposure control limits should be updated as well. Add this to the camera sensor documentation. Signed-off-by: Jacopo Mondi --- .../driver-api/media/camera-sensor.rst | 36 +++++++++++++++++++ 1 file changed, 36 insertions(+) -- 2.38.1 diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst index 382ea4ecebd4..675f55ad54b5 100644 --- a/Documentation/driver-api/media/camera-sensor.rst +++ b/Documentation/driver-api/media/camera-sensor.rst @@ -184,3 +184,39 @@ used to obtain device's power state after the power state transition: The function returns a non-zero value if it succeeded getting the power count or runtime PM was disabled, in either of which cases the driver may proceed to access the device. + +Resetting exposure limits on vertical blanking update +""""""""""""""""""""""""""""""""""""""""""""""""""""" + +The sensor exposure time, specified by the ``V4L2_CID_EXPOSURE`` control, is +usually limited to a maximum value related to the frame interval. Frequently it +is a number of lines less than the frame length that will be specified in the +sensor documentation. + +When a new ``V4L2_CID_VBLANK`` value is applied, regardless of it being actually +programmed to the hardware or not, the limits of the ``V4L2_CID_EXPOSURE`` +control should be updated as well. + +The typical coding pattern that realizes that in the ``.s_ctrl`` callback +handler is: + +.. code-block:: c + + #define SENSOR_EXPOSURE_OFFSET + + static int s_ctrl(struct v4l2_ctrl *ctrl) + { + int exp_max; + + switch (ctrl->id) { + case V4L2_CID_VBLANK: + exp_max = (analogue crop height) + ctrl->val - SENSOR_EXPOSURE_OFFSET; + __v4l2_ctrl_modify_range(sensor->ctrls.exposure, + sensor->ctrls.exposure->minimum, + exp_max, sensor->ctrls.exposure->step, + sensor->ctrls.exposure->default_value); + break; + } + + if (!pm_runtime_get_if_in_use(&sensor->i2c_client->dev)) + return 0;