From nobody Thu Oct 2 02:15:08 2025 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE74F3019C1; Thu, 25 Sep 2025 15:55:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758815733; cv=none; b=eN52amSnVXYcl9msp02J2I+XytG8LFY1R1WwxK/Pb7AHlXOGd60aDezFEs67tjgw8/pTeY3ZfWxxEgac73dJASO3mZ+9iTyfYsKyTX0majW5e+cLVVQdX+Z+sWcO/uhuRH8s6bV0m9prb7WXJ35GWhK0EtLQskxTyDK2l363GZA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758815733; c=relaxed/simple; bh=0eohwAR/y++4oPMxRnpqozTlsghcWn2K5MPx0wPe8gg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=u1MElmGt3GfPibKirGZUJwQbUQXTY+BdGWsiuJl5IrFADTrnoMFbTyoNgGNK2AIvNAzVPFW6+er6jHWDv5ZbxgiLhIsm5zhQhWAdtqH1fihPctT/r+/RfIETg1oRnumOAa1KAuw9jfCJqegu4ufUlsOqboOJ6wLoVWzG51OPgKQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=mcs2YirO; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="mcs2YirO" Received: from [127.0.1.1] (cpc89244-aztw30-2-0-cust6594.18-1.cable.virginm.net [86.31.185.195]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 628B21D1C; Thu, 25 Sep 2025 17:54:01 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1758815642; bh=0eohwAR/y++4oPMxRnpqozTlsghcWn2K5MPx0wPe8gg=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=mcs2YirOd9cwzKG03SPsBv9Hu8SCoekmPeGuYhxWzmjddYDdUZlXWueul6Gl41IYx OlSU4tm4LTT8NyUg7pGfK2BAw7s9Sznpt2dx178Xg0suyV0meuVCt35XXyToGzG51e Xy1ALGMN1+X/f0UGnFoTTnMuTD/J6JnE42tAkOCY= From: Isaac Scott Date: Thu, 25 Sep 2025 16:54:26 +0100 Subject: [PATCH v4 1/4] media: v4l: Add helper to get number of active lanes via a pad Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250925-active-data-lanes-v4-1-8b54e3d5af6c@ideasonboard.com> References: <20250925-active-data-lanes-v4-0-8b54e3d5af6c@ideasonboard.com> In-Reply-To: <20250925-active-data-lanes-v4-0-8b54e3d5af6c@ideasonboard.com> To: Mauro Carvalho Chehab , Rui Miguel Silva , Laurent Pinchart , Martin Kepplinger , Purism Kernel Team , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Sakari Ailus Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Isaac Scott , Frank Li X-Mailer: b4 0.13.0 Sometimes, users will not use all of the MIPI CSI 2 lanes available when connecting to the MIPI CSI receiver of their device. Add a helper function that checks the mbus_config for the device driver to allow users to define the number of active data lanes through the get_mbus_config op. If the driver does not implement this op, fall back to using the maximum number of lanes available. Reviewed-by: Frank Li Reviewed-by: Laurent Pinchart Signed-off-by: Isaac Scott --- drivers/media/v4l2-core/v4l2-common.c | 29 +++++++++++++++++++++++++++++ include/media/v4l2-common.h | 20 ++++++++++++++++++++ 2 files changed, 49 insertions(+) diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-cor= e/v4l2-common.c index b367d479d6b3..2b4cec25e751 100644 --- a/drivers/media/v4l2-core/v4l2-common.c +++ b/drivers/media/v4l2-core/v4l2-common.c @@ -573,6 +573,35 @@ s64 v4l2_get_link_freq(const struct media_pad *pad, un= signed int mul, return v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div); } EXPORT_SYMBOL_GPL(v4l2_get_link_freq); + +unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad, + unsigned int max_data_lanes) +{ + struct v4l2_mbus_config mbus_config =3D {}; + struct v4l2_subdev *sd; + unsigned int lanes; + int ret; + + sd =3D media_entity_to_v4l2_subdev(pad->entity); + ret =3D v4l2_subdev_call(sd, pad, get_mbus_config, pad->index, + &mbus_config); + if (ret < 0 && ret !=3D -ENOIOCTLCMD) + return ret; + + /* This relies on the mbus_config being zeroed at init time */ + lanes =3D mbus_config.bus.mipi_csi2.num_data_lanes; + if (!lanes) + return max_data_lanes; + + if (lanes > max_data_lanes) { + dev_dbg(sd->dev, "Active data lanes (%u) exceeds max (%u)\n", + lanes, max_data_lanes); + return -EINVAL; + } + + return lanes; +} +EXPORT_SYMBOL_GPL(v4l2_get_active_data_lanes); #endif =20 /* diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h index 5c0a7f6b5bb6..950df46cb27a 100644 --- a/include/media/v4l2-common.h +++ b/include/media/v4l2-common.h @@ -581,6 +581,26 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane = *pixfmt, u32 pixelformat, #ifdef CONFIG_MEDIA_CONTROLLER s64 v4l2_get_link_freq(const struct media_pad *pad, unsigned int mul, unsigned int div); + +/** + * v4l2_get_active_data_lanes - Get number of active data lanes from driver + * + * @pad: The transmitter's media pad. + * @max_data_lanes: The maximum number of active data lanes supported by + * the MIPI CSI link in hardware. + * + * This function is intended for obtaining the number of data lanes that a= re + * actively being used by the driver for a MIPI CSI-2 device on a given me= dia pad. + * This information is derived from a mbus_config fetched from a device dr= iver + * using the get_mbus_config v4l2_subdev pad op. + * + * Return: + * * >0: Number of active data lanes + * * %-EINVAL: Number of active data lanes is invalid, as it exceeds the m= aximum + * supported data lanes. + */ +unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad, + unsigned int max_data_lanes); #endif =20 void v4l2_simplify_fraction(u32 *numerator, u32 *denominator, --=20 2.43.0