Message-ID: <903d0948-0bc0-9f09-213b-5f650cc8762b@xs4all.nl>
Date:   Tue, 20 Feb 2018 14:25:13 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Alexandre Courbot <acourbot@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Pawel Osciak <posciak@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Gustavo Padovan <gustavo.padovan@...labora.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFCv4 09/21] v4l2: add request API support

On 02/20/18 05:44, Alexandre Courbot wrote:
> Add a v4l2 request entity data structure that takes care of storing the
> request-related state of a V4L2 device ; in this case, its controls.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...omium.org>
> ---
>  drivers/media/v4l2-core/Makefile       |   1 +
>  drivers/media/v4l2-core/v4l2-request.c | 178 +++++++++++++++++++++++++
>  include/media/v4l2-request.h           | 159 ++++++++++++++++++++++
>  3 files changed, 338 insertions(+)
>  create mode 100644 drivers/media/v4l2-core/v4l2-request.c
>  create mode 100644 include/media/v4l2-request.h
> 
> diff --git a/drivers/media/v4l2-core/Makefile b/drivers/media/v4l2-core/Makefile
> index 80de2cb9c476..13d0477535bd 100644
> --- a/drivers/media/v4l2-core/Makefile
> +++ b/drivers/media/v4l2-core/Makefile
> @@ -16,6 +16,7 @@ ifeq ($(CONFIG_TRACEPOINTS),y)
>    videodev-objs += vb2-trace.o v4l2-trace.o
>  endif
>  videodev-$(CONFIG_MEDIA_CONTROLLER) += v4l2-mc.o
> +videodev-$(CONFIG_MEDIA_REQUEST_API) += v4l2-request.o
>  
>  obj-$(CONFIG_VIDEO_V4L2) += videodev.o
>  obj-$(CONFIG_VIDEO_V4L2) += v4l2-common.o
> diff --git a/drivers/media/v4l2-core/v4l2-request.c b/drivers/media/v4l2-core/v4l2-request.c
> new file mode 100644
> index 000000000000..e8ad10e2f525
> --- /dev/null
> +++ b/drivers/media/v4l2-core/v4l2-request.c
> @@ -0,0 +1,178 @@
> +/*
> + * Media requests support for V4L2
> + *
> + * Copyright (C) 2018, The Chromium OS Authors.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/slab.h>
> +
> +#include <media/v4l2-dev.h>
> +#include <media/v4l2-request.h>
> +#include <media/videobuf2-v4l2.h>
> +
> +void v4l2_request_entity_init(struct v4l2_request_entity *entity,
> +			      const struct media_request_entity_ops *ops,
> +			      struct video_device *vdev)
> +{
> +	media_request_entity_init(&entity->base, MEDIA_REQUEST_ENTITY_TYPE_V4L2, ops);
> +	entity->vdev = vdev;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_request_entity_init);
> +
> +struct media_request_entity_data *
> +v4l2_request_entity_data_alloc(struct media_request *req,
> +			       struct v4l2_ctrl_handler *hdl)
> +{
> +	struct v4l2_request_entity_data *data;
> +	int ret;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ret = v4l2_ctrl_request_init(&data->ctrls);
> +	if (ret) {
> +		kfree(data);
> +		return ERR_PTR(ret);
> +	}
> +	ret = v4l2_ctrl_request_clone(&data->ctrls, hdl, NULL);
> +	if (ret) {
> +		kfree(data);
> +		return ERR_PTR(ret);
> +	}
> +
> +	INIT_LIST_HEAD(&data->queued_buffers);
> +
> +	return &data->base;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_request_entity_data_alloc);
> +
> +void v4l2_request_entity_data_free(struct media_request_entity_data *_data)
> +{
> +	struct v4l2_request_entity_data *data;
> +	struct v4l2_vb2_request_buffer *qb, *n;
> +
> +	data = to_v4l2_entity_data(_data);
> +
> +	list_for_each_entry_safe(qb, n, &data->queued_buffers, node) {
> +		struct vb2_buffer *buf;
> +		dev_warn(_data->request->mgr->dev,
> +			 "entity data freed while buffer still queued!\n");
> +
> +		/* give buffer back to user-space */
> +		buf = qb->queue->bufs[qb->v4l2_buf.index];
> +		buf->state = qb->pre_req_state;
> +		buf->request = NULL;
> +
> +		kfree(qb);
> +	}
> +
> +	v4l2_ctrl_handler_free(&data->ctrls);
> +	kfree(data);
> +}
> +EXPORT_SYMBOL_GPL(v4l2_request_entity_data_free);
> +
> +
> +
> +
> +
> +static struct media_request *v4l2_request_alloc(struct media_request_mgr *mgr)
> +{
> +	struct media_request *req;
> +
> +	req = kzalloc(sizeof(*req), GFP_KERNEL);
> +	if (!req)
> +		return ERR_PTR(-ENOMEM);
> +
> +	req->mgr = mgr;
> +	req->state = MEDIA_REQUEST_STATE_IDLE;
> +	INIT_LIST_HEAD(&req->data);
> +	init_waitqueue_head(&req->complete_wait);
> +	mutex_init(&req->lock);
> +
> +	mutex_lock(&mgr->mutex);
> +	list_add_tail(&req->list, &mgr->requests);
> +	mutex_unlock(&mgr->mutex);
> +
> +	return req;
> +}
> +
> +static void v4l2_request_free(struct media_request *req)
> +{
> +	struct media_request_mgr *mgr = req->mgr;
> +	struct media_request_entity_data *data, *next;
> +
> +	mutex_lock(&mgr->mutex);
> +	list_del(&req->list);
> +	mutex_unlock(&mgr->mutex);
> +
> +	list_for_each_entry_safe(data, next, &req->data, list) {
> +		list_del(&data->list);
> +		data->entity->ops->data_free(data);
> +	}
> +
> +	kfree(req);
> +}
> +
> +static bool v4l2_entity_valid(const struct media_request *req,
> +			      const struct media_request_entity *_entity)
> +{
> +	const struct v4l2_request_mgr *mgr;
> +	const struct v4l2_request_entity *entity;
> +
> +	if (_entity->type != MEDIA_REQUEST_ENTITY_TYPE_V4L2)
> +		return false;
> +
> +	entity = container_of(_entity, struct v4l2_request_entity, base);
> +	mgr = container_of(req->mgr, struct v4l2_request_mgr, base);
> +
> +	/* Entity is valid if it is the video device that created the manager */
> +	return entity->vdev == mgr->vdev;
> +}
> +
> +static int v4l2_request_submit(struct media_request *req)
> +{
> +	struct media_request_entity_data *data;
> +
> +        /* Submit for each entity */
> +	list_for_each_entry(data, &req->data, list) {
> +		int ret = data->entity->ops->submit(req, data);
> +		/* TODO proper error handling, abort on other entities? */
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +const struct media_request_ops v4l2_request_ops = {
> +	.alloc = v4l2_request_alloc,
> +	.release = v4l2_request_free,
> +	.entity_valid = v4l2_entity_valid,
> +	.submit = v4l2_request_submit,
> +};
> +EXPORT_SYMBOL_GPL(v4l2_request_ops);
> +
> +void v4l2_request_mgr_init(struct v4l2_request_mgr *mgr,
> +			  struct video_device *vdev,
> +			  const struct media_request_ops *ops)
> +{
> +	media_request_mgr_init(&mgr->base, &vdev->dev, ops);
> +	mgr->vdev = vdev;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_request_mgr_init);
> +
> +void v4l2_request_mgr_free(struct v4l2_request_mgr* mgr)
> +{
> +	media_request_mgr_free(&mgr->base);
> +}
> +EXPORT_SYMBOL_GPL(v4l2_request_mgr_free);
> diff --git a/include/media/v4l2-request.h b/include/media/v4l2-request.h
> new file mode 100644
> index 000000000000..8a87ca455b74
> --- /dev/null
> +++ b/include/media/v4l2-request.h
> @@ -0,0 +1,159 @@
> +/*
> + * Media requests support for V4L2
> + *
> + * Copyright (C) 2018, The Chromium OS Authors.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef _MEDIA_V4L2_REQUEST_H
> +#define _MEDIA_V4L2_REQUEST_H
> +
> +#include <linux/kconfig.h>
> +#include <media/media-request.h>
> +
> +#if IS_ENABLED(CONFIG_MEDIA_REQUEST_API)
> +
> +#include <linux/list.h>
> +
> +#include <media/videobuf2-core.h>
> +#include <media/v4l2-ctrls.h>
> +
> +/**
> + * struct v4l2_request_entity - entity used with V4L2 instances
> + *
> + * @base:	base media_request_entity struct
> + * @vdev:	video device that this entity represents
> + *
> + * This structure is used by V4L2 devices that support being controlled
> + * by requests. If should be added to the device-specific structure that the

If -> It

> + * driver wishes to control using requests.
> + *
> + * V4L2 request entities are able to receive queued buffers using vb2 queues,
> + * and control settings using the control framework.
> + *
> + */
> +struct v4l2_request_entity {
> +	struct media_request_entity base;
> +	struct video_device *vdev;
> +};
> +#define to_v4l2_entity(e) container_of(e, struct v4l2_request_entity, base)
> +
> +/**
> + * v4l2_request_entity_init() - initialize a struct v4l2_request_entity
> + *
> + * @entity:	entity to initialize
> + * @ops:	entity ops to use
> + * @vdev:	video device represented by this entity
> + */
> +void v4l2_request_entity_init(struct v4l2_request_entity *entity,
> +			      const struct media_request_entity_ops *ops,
> +			      struct video_device *vdev);
> +
> +/**
> + * struct v4l2_vb2_request_buffer - record buffer queue on behalf of a request
> + *
> + * @queue:		vb2 queue
> + * @pre_req_state:	keep track of the pre-QBUF state of the buffer
> + * @v4l2_buf:		user-space buffer queue ioctl data
> + * @node:		entry into v4l2_request_entity_data::queued_buffers
> + */
> +struct v4l2_vb2_request_buffer {
> +	struct vb2_queue *queue;
> +	enum vb2_buffer_state pre_req_state;
> +	struct v4l2_buffer v4l2_buf;
> +	struct list_head node;
> +};
> +
> +/**
> + * struct v4l2_request_entity_data - per-request data for V4L2 entities
> + *
> + * @base:		base entity data structure
> + * @ctrls:		record of controls set for this request
> + * @queued_buffers:	record of buffers queued for this request
> + */
> +struct v4l2_request_entity_data {
> +	struct media_request_entity_data base;
> +	struct v4l2_ctrl_handler ctrls;

Please call this field either 'hdl' or 'ctrl_handler'. 'ctrls' is very
confusing. That way I know it represents a control handler and not a
list or array of controls.

> +	struct list_head queued_buffers;
> +};
> +static inline struct v4l2_request_entity_data *
> +to_v4l2_entity_data(struct media_request_entity_data *data)
> +{
> +	if (IS_ERR(data))
> +		return (struct v4l2_request_entity_data *)data;
> +
> +	return container_of(data, struct v4l2_request_entity_data, base);
> +}
> +
> +/**
> + * v4l2_request_entity_data_alloc() - allocate data for a V4L2 entity
> + *
> + * @req:	request to allocate for
> + * @hdl:	control handler of the device we will be controlling
> + *
> + * Helper function to be used from the media_request_entity_ops::data_alloc
> + * hook.
> + */
> +struct media_request_entity_data *
> +v4l2_request_entity_data_alloc(struct media_request *req,
> +			       struct v4l2_ctrl_handler *hdl);
> +
> +/**
> + * v4l2_request_entity_data_free() - free per-request data of an entity
> + *
> + * @data:	entity data to free
> + *
> + * Helper function to be usedfrom the media_request_entity_ops::data_free
> + * hook.
> + */
> +void
> +v4l2_request_entity_data_free(struct media_request_entity_data *_data);
> +
> +
> +
> +
> +
> +/**
> + * struct v4l2_request_mgr - request manager producing requests suitable
> + *			     for managing single v4l2 devices.
> + *
> + * @base:	base manager structure
> + * @vdev:	device that our requests can control
> + */
> +struct v4l2_request_mgr {
> +	struct media_request_mgr base;
> +	struct video_device *vdev;
> +};
> +
> +/**
> + * v4l2_request_mgr_init() - initialize a v4l2_request_mgr
> + *
> + * @mgr:	manager to initialize
> + * @vdev:	video device that our instances will control
> + * @ops:	used to override ops if needed. &v4l2_request_ops is a good
> + *		default
> + */
> +void v4l2_request_mgr_init(struct v4l2_request_mgr *mgr,
> +			  struct video_device *vdev,
> +			  const struct media_request_ops *ops);
> +
> +/**
> + * v4l2_request_mgr_free() - free a v4l2 request manager
> + *
> + * @mgr:	manager to free
> + */
> +void v4l2_request_mgr_free(struct v4l2_request_mgr *mgr);
> +
> +extern const struct media_request_ops v4l2_request_ops;
> +
> +#endif /* CONFIG_MEDIA_REQUEST_API */
> +
> +#endif
> 

I'm not convinced by some of the naming, but I'll get back to that later.

Also very unclear is which objects here are refcounted and which have to
be manually freed. My control handler patch series adds a kref to struct
v4l2_ctrl_handler, but that isn't used AFAICT.

I will probably come back to this as well.

Regards,

	Hans

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