From mboxrd@z Thu Jan 1 00:00:00 1970 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 52BBBCA4E; Mon, 6 Oct 2025 08:15:53 +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=1759738557; cv=none; b=N8ykjAhwc4f4QGKC5rG3QuulgSDuGuNKE+HSCCIk69aiEIVrNoD+UUtbWfAWxx5uheQoGA40gZD879G5SQHuieJEeqBvv9vIUXKhni4eaIgn2CBj4TUCSczUile5QeTKcC1KBb0Qat5F0YJ1yNN1eVZgp5+Rf+57voN6XItDiqY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759738557; c=relaxed/simple; bh=s+3UODTI3yceI/ljvsYlUDNrB5ALwX7Lh3D6vFzcj9w=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YSpUxN4oA+bAPvtT9/D/tx/3qznBmzYM2Pv+4DSJWIpuCHo4QTX7HtpBInrEbrwlOrQMg4Uq5zNZ487NrmRGGB/XhVFSigJ9Ao0fJr1VvI7nD+/s7/ON3vQI7jFw1D+aOPdEc+5E2cA66GQ++24dfaqw65f84kyVa3jF6+tghTo= 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=wQctDyBz; 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="wQctDyBz" Received: from [192.168.0.43] (cpc141996-chfd3-2-0-cust928.12-3.cable.virginm.net [86.13.91.161]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 77F43BD2; Mon, 6 Oct 2025 10:14:18 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1759738458; bh=s+3UODTI3yceI/ljvsYlUDNrB5ALwX7Lh3D6vFzcj9w=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=wQctDyBzrAfrzYscIaBwX8a8KiLOGw3yWyqUllR8XIw2yLX+KuI5CDLva2d31NkTW J9MY+81/mC0sWgFg7r2RH7SfAO0mRx8FJ/xVYosaOtGCWgdwwOSoi26jVOt8s177AJ b3a4dsNt2RV2tluztitcFCaDBqYzvwybX+89AzMU= Message-ID: Date: Mon, 6 Oct 2025 09:15:47 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 1/8] media: uapi: Introduce V4L2 generic ISP types To: Laurent Pinchart , Jacopo Mondi Cc: Dafna Hirschfeld , Keke Li , Mauro Carvalho Chehab , Heiko Stuebner , Sakari Ailus , Antoine Bouyer , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org References: <20250915-extensible-parameters-validation-v5-0-e6db94468af3@ideasonboard.com> <20250915-extensible-parameters-validation-v5-1-e6db94468af3@ideasonboard.com> <20251005000602.GA13055@pendragon.ideasonboard.com> Content-Language: en-US From: Dan Scally In-Reply-To: <20251005000602.GA13055@pendragon.ideasonboard.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Morning Laurent, Jacopo On 05/10/2025 01:06, Laurent Pinchart wrote: > Hi Jacopo, > > Thank you for the patch. > > On Mon, Sep 15, 2025 at 07:18:10PM +0200, Jacopo Mondi wrote: >> Introduce v4l2-isp.h in the Linux kernel uAPI. >> >> The header includes types for generic ISP configuration parameters >> and will be extended in future with support for generic ISP statistics > > s/in future/in the future/ > > (and you can reflow the commit message) > >> formats. >> >> Generic ISP parameters support is provided by introducing two new >> types that represent an extensible and versioned buffer of ISP >> configuration parameters. >> >> The v4l2_params_block_header structure represents the header to be >> prepend to each ISP configuration block and the v4l2_params_buffer type >> represents the base type for the configuration parameters buffer. > > The second part of the sentence describes the same structure as the next > paragraph. > >> The v4l2_params_buffer represents the container for the ISP >> configuration data block. The generic type is defined with a 0-sized >> data member that the ISP driver implementations shall properly size >> according to their capabilities. > > This will be easier to understand if you describe v4l2_params_buffer > first. > > The commit message would benefit from being rewritten. > >> [Add v4l2_params_buffer_size()] >> Signed-off-by: Daniel Scally >> Reviewed-by: Daniel Scally >> Signed-off-by: Jacopo Mondi >> --- >> MAINTAINERS | 6 +++ >> include/uapi/linux/media/v4l2-isp.h | 100 ++++++++++++++++++++++++++++++++++++ >> 2 files changed, 106 insertions(+) >> >> diff --git a/MAINTAINERS b/MAINTAINERS >> index ee8cb2db483f6a5e96b62b6f2edd05b1427b69f5..e82c3d0758d6033fe8fcd56ffde2c03c4319fd11 100644 >> --- a/MAINTAINERS >> +++ b/MAINTAINERS >> @@ -26410,6 +26410,12 @@ F: drivers/media/i2c/vd55g1.c >> F: drivers/media/i2c/vd56g3.c >> F: drivers/media/i2c/vgxy61.c >> >> +V4L2 GENERIC ISP PARAMETERS AND STATISTIC FORMATS >> +M: Jacopo Mondi >> +L: linux-media@vger.kernel.org >> +S: Maintained >> +F: include/uapi/linux/media/v4l2-isp.h >> + >> VF610 NAND DRIVER >> M: Stefan Agner >> L: linux-mtd@lists.infradead.org >> diff --git a/include/uapi/linux/media/v4l2-isp.h b/include/uapi/linux/media/v4l2-isp.h >> new file mode 100644 >> index 0000000000000000000000000000000000000000..b838555dce2b290a14136ab09ea4d2dfdc95b26b >> --- /dev/null >> +++ b/include/uapi/linux/media/v4l2-isp.h >> @@ -0,0 +1,100 @@ >> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ >> +/* >> + * Video4Linux2 generic ISP parameters and statistics support >> + * >> + * Copyright (C) 2025 Ideas On Board Oy >> + * Author: Jacopo Mondi >> + */ >> + >> +#ifndef _UAPI_V4L2_ISP_H_ >> +#define _UAPI_V4L2_ISP_H_ >> + >> +#include >> +#include >> + >> +#define V4L2_PARAMS_FL_BLOCK_DISABLE (1U << 0) >> +#define V4L2_PARAMS_FL_BLOCK_ENABLE (1U << 1) >> + >> +/* >> + * Reserve the first 8 bits for V4L2_PARAMS_FL_* flag. >> + * >> + * Driver-specific flags should be defined as: >> + * #define PLATFORM_SPECIFIC_FLAG0 ((1U << V4L2_PARAMS_FL_DRIVER_FLAGS(0)) > > s/PLATFORM/DRIVER/ > >> + * #define PLATFORM_SPECIFIC_FLAG1 ((1U << V4L2_PARAMS_FL_DRIVER_FLAGS(1)) >> + */ >> +#define V4L2_PARAMS_FL_DRIVER_FLAGS(n) ((n) + 8) >> + >> +/** >> + * struct v4l2_params_block_header - V4L2 extensible parameters block header >> + * >> + * This structure represents the common part of all the ISP configuration >> + * blocks. Each parameters block shall embed an instance of this structure type >> + * as its first member, followed by the block-specific configuration data. The >> + * driver inspects this common header to discern the block type and its size and >> + * properly handle the block content. > > The last sentence is not relevant for the UAPI. > >> + * >> + * The @type field is an ISP driver-specific value that identifies the block >> + * type. The @size field specifies the size of the parameters block. >> + * >> + * The @flags field is a bitmask of per-block flags V4L2_PARAMS_FL_* and >> + * driver-specific flags specified by the driver header. >> + * >> + * @type: The parameters block type (driver-specific) >> + * @flags: A bitmask of block flags (driver-specific) >> + * @size: Size (in bytes) of the parameters block, including this header > > I think the fields usually go right after the structure name, followed > by the rest of the documentation. > >> + */ >> +struct v4l2_params_block_header { >> + __u16 type; >> + __u16 flags; >> + __u32 size; >> +} __attribute__((aligned(8))); >> + >> +/** >> + * v4l2_params_buffer_size - Calculate size of v4l2_params_buffer for a platform >> + * >> + * Users of the v4l2 extensible parameters will have differing sized data arrays >> + * depending on their specific parameter buffers. Drivers and userspace will >> + * need to be able to calculate the appropriate size of the struct to >> + * accommodate all ISP configuration blocks provided by the platform. >> + * This macro provides a convenient tool for the calculation. >> + * >> + * @max_params_size: The total size of the ISP configuration blocks >> + */ >> +#define v4l2_params_buffer_size(max_params_size) \ >> + (offsetof(struct v4l2_params_buffer, data) + (max_params_size)) > > This isn't used in this series as far as I can tell, and neither is it > used in your libcamera implementation. I'd drop the macro (as well as > the mention in the commit message). This is because the rkisp1 and c3 ISP implementations are already merged with a custom parameters buffer struct defined at [1] and [2]. There the array size is set to the max size macro. This series just asserts that the header part is a size match for struct v4l2_params_buffer to guarantee compatibility, so throughout those drivers they can use sizeof(struct c3_isp_params_cfg) or the rkisp equivalent and it's fine. For new users that don't have a custom struct in their uAPI and are relying on struct v4l2_params_buffer we can't just do sizeof(), so the idea was for this to provide a canonical way for the size calculation to be done across both the kernel and userspace. If we decide that it's worth keeping but want a user in this series to justify its inclusion, it could be used in patches 2 and 3 - I'll reply to patch 2 in a second to indicate where. Thanks Dan [1] https://elixir.bootlin.com/linux/v6.17/source/include/uapi/linux/rkisp1-config.h#L1675 [2] https://elixir.bootlin.com/linux/v6.17/source/include/uapi/linux/media/amlogic/c3-isp-config.h#L558> >> + >> +/** >> + * struct v4l2_params_buffer - V4L2 extensible parameters configuration >> + * >> + * This struct contains the configuration parameters of the ISP algorithms, > > s/struct/structure/ > >> + * serialized by userspace into a data buffer. Each configuration parameter >> + * block is represented by a block-specific structure which contains a >> + * :c:type:`v4l2_params_block_header` entry as first member. Userspace populates >> + * the @data buffer with configuration parameters for the blocks that it intends >> + * to configure. As a consequence, the data buffer effective size changes >> + * according to the number of ISP blocks that userspace intends to configure and >> + * is set by userspace in the @data_size field. >> + * >> + * The parameters buffer is versioned by the @version field to allow modifying >> + * and extending its definition. Userspace shall populate the @version field to >> + * inform the driver about the version it intends to use. The driver will parse >> + * and handle the @data buffer according to the data layout specific to the >> + * indicated version and return an error if the desired version is not >> + * supported. >> + * >> + * For each ISP block that userspace wants to configure, a block-specific >> + * structure is appended to the @data buffer, one after the other without gaps >> + * in between nor overlaps. Userspace shall populate the @data_size field with > > I think you can drop "nor overlaps", nobody in their right mind should > think the blocks could be overlayed :-) > >> + * the effective size, in bytes, of the @data buffer. >> + * >> + * @version: The parameters buffer version (driver-specific) >> + * @data_size: The configuration data effective size, excluding this header >> + * @data: The configuration data > > Move the fields up just after the structure name. > > Reviewed-by: Laurent Pinchart > >> + */ >> +struct v4l2_params_buffer { >> + __u32 version; >> + __u32 data_size; >> + __u8 data[] __counted_by(data_size); >> +}; >> + >> +#endif /* _UAPI_V4L2_ISP_H_ */ >