From patchwork Mon Nov 7 20:49:59 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jacopo Mondi X-Patchwork-Id: 622524 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 62C41C43217 for ; Mon, 7 Nov 2022 20:50:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233062AbiKGUu1 (ORCPT ); Mon, 7 Nov 2022 15:50:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233056AbiKGUu0 (ORCPT ); Mon, 7 Nov 2022 15:50:26 -0500 Received: from relay9-d.mail.gandi.net (relay9-d.mail.gandi.net [217.70.183.199]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB6BA1E3D5 for ; Mon, 7 Nov 2022 12:50:23 -0800 (PST) Received: (Authenticated sender: jacopo@jmondi.org) by mail.gandi.net (Postfix) with ESMTPSA id 5E2CBFF80C; Mon, 7 Nov 2022 20:50:21 +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 3/3] documentation: media: camera_sensor: Update exposure on blanking change Date: Mon, 7 Nov 2022 21:49:59 +0100 Message-Id: <20221107204959.37691-4-jacopo@jmondi.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221107204959.37691-1-jacopo@jmondi.org> References: <20221107204959.37691-1-jacopo@jmondi.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org 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 | 33 +++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst index 31f74f85ebc5..76206c7647d6 100644 --- a/Documentation/driver-api/media/camera-sensor.rst +++ b/Documentation/driver-api/media/camera-sensor.rst @@ -179,3 +179,36 @@ 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 on vertical blanking update +"""""""""""""""""""""""""""""""""""""""""""""" + +The sensor exposure time, specified by the ``V4L2_CID_EXPOSURE`` control, is +usually limited by a maximum value which is equal to maximum vertical blankings +minus a known offset usually specified in the chip programming manual. + +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 + + static int s_ctrl(struct v4l2_ctrl *ctrl) + { + int exp_max; + + switch (ctrl->id) { + case V4L2_CID_VBLANK: + exp_max = sensor->fmt.height + ctrl->val - 4; + __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;