// SPDX-License-Identifier: GPL-2.0
/*
 * Xilinx Video DMA
 *
 * Copyright (C) 2013-2015 Ideas on Board
 * Copyright (C) 2013-2015 Xilinx, Inc.
 *
 * Contacts: Hyun Kwon <hyun.kwon@xilinx.com>
 *           Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 */

#include <linux/dma/xilinx_dma.h>
#include <linux/lcm.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/slab.h>

#include <media/v4l2-dev.h>
#include <media/v4l2-fh.h>
#include <media/v4l2-ioctl.h>
#include <media/videobuf2-v4l2.h>
#include <media/videobuf2-dma-contig.h>

#include "xilinx-dma.h"
#include "xilinx-vip.h"
#include "xilinx-vipp.h"

#define XVIP_DMA_DEF_FORMAT             V4L2_PIX_FMT_YUYV
#define XVIP_DMA_DEF_WIDTH              1920
#define XVIP_DMA_DEF_HEIGHT             1080

/* Minimum and maximum widths are expressed in bytes */
#define XVIP_DMA_MIN_WIDTH              1U
#define XVIP_DMA_MAX_WIDTH              65535U
#define XVIP_DMA_MIN_HEIGHT             1U
#define XVIP_DMA_MAX_HEIGHT             8191U

/* -----------------------------------------------------------------------------
 * Helper functions
 */

static struct v4l2_subdev *
xvip_dma_remote_subdev(struct media_pad *local, u32 *pad)
{
        struct media_pad *remote;

        remote = media_entity_remote_pad(local);
        if (!remote || !is_media_entity_v4l2_subdev(remote->entity))
                return NULL;

        if (pad)
                *pad = remote->index;

        return media_entity_to_v4l2_subdev(remote->entity);
}

static int xvip_dma_verify_format(struct xvip_dma *dma)
{
        struct v4l2_subdev_format fmt;
        struct v4l2_subdev *subdev;
        int ret;

        subdev = xvip_dma_remote_subdev(&dma->pad, &fmt.pad);
        if (subdev == NULL)
                return -EPIPE;

        fmt.which = V4L2_SUBDEV_FORMAT_ACTIVE;
        ret = v4l2_subdev_call(subdev, pad, get_fmt, NULL, &fmt);
        if (ret < 0)
                return ret == -ENOIOCTLCMD ? -EINVAL : ret;

        if (dma->fmtinfo->code != fmt.format.code ||
            dma->format.height != fmt.format.height ||
            dma->format.width != fmt.format.width ||
            dma->format.colorspace != fmt.format.colorspace)
                return -EINVAL;

        return 0;
}

/* -----------------------------------------------------------------------------
 * Pipeline Stream Management
 */

/**
 * xvip_pipeline_start_stop - Start ot stop streaming on a pipeline
 * @pipe: The pipeline
 * @start: Start (when true) or stop (when false) the pipeline
 *
 * Walk the entities chain starting at the pipeline output video node and start
 * or stop all of them.
 *
 * Return: 0 if successful, or the return value of the failed video::s_stream
 * operation otherwise.
 */
static int xvip_pipeline_start_stop(struct xvip_pipeline *pipe, bool start)
{
        struct xvip_dma *dma = pipe->output;
        struct media_entity *entity;
        struct media_pad *pad;
        struct v4l2_subdev *subdev;
        int ret;

        entity = &dma->video.entity;
        while (1) {
                pad = &entity->pads[0];
                if (!(pad->flags & MEDIA_PAD_FL_SINK))
                        break;

                pad = media_entity_remote_pad(pad);
                if (!pad || !is_media_entity_v4l2_subdev(pad->entity))
                        break;

                entity = pad->entity;
                subdev = media_entity_to_v4l2_subdev(entity);

                ret = v4l2_subdev_call(subdev, video, s_stream, start);
                if (start && ret < 0 && ret != -ENOIOCTLCMD)
                        return ret;
        }

        return 0;
}

/**
 * xvip_pipeline_set_stream - Enable/disable streaming on a pipeline
 * @pipe: The pipeline
 * @on: Turn the stream on when true or off when false
 *
 * The pipeline is shared between all DMA engines connect at its input and
 * output. While the stream state of DMA engines can be controlled
 * independently, pipelines have a shared stream state that enable or disable
 * all entities in the pipeline. For this reason the pipeline uses a streaming
 * counter that tracks the number of DMA engines that have requested the stream
 * to be enabled.
 *
 * When called with the @on argument set to true, this function will increment
 * the pipeline streaming count. If the streaming count reaches the number of
 * DMA engines in the pipeline it will enable all entities that belong to the
 * pipeline.
 *
 * Similarly, when called with the @on argument set to false, this function will
 * decrement the pipeline streaming count and disable all entities in the
 * pipeline when the streaming count reaches zero.
 *
 * Return: 0 if successful, or the return value of the failed video::s_stream
 * operation otherwise. Stopping the pipeline never fails. The pipeline state is
 * not updated when the operation fails.
 */
static int xvip_pipeline_set_stream(struct xvip_pipeline *pipe, bool on)
{
        int ret = 0;

        mutex_lock(&pipe->lock);

        if (on) {
                if (pipe->stream_count == pipe->num_dmas - 1) {
                        ret = xvip_pipeline_start_stop(pipe, true);
                        if (ret < 0)
                                goto done;
                }
                pipe->stream_count++;
        } else {
                if (--pipe->stream_count == 0)
                        xvip_pipeline_start_stop(pipe, false);
        }

done:
        mutex_unlock(&pipe->lock);
        return ret;
}

static int xvip_pipeline_validate(struct xvip_pipeline *pipe,
                                  struct xvip_dma *start)
{
        struct media_graph graph;
        struct media_entity *entity = &start->video.entity;
        struct media_device *mdev = entity->graph_obj.mdev;
        unsigned int num_inputs = 0;
        unsigned int num_outputs = 0;
        int ret;

        mutex_lock(&mdev->graph_mutex);

        /* Walk the graph to locate the video nodes. */
        ret = media_graph_walk_init(&graph, mdev);
        if (ret) {
                mutex_unlock(&mdev->graph_mutex);
                return ret;
        }

        media_graph_walk_start(&graph, entity);

        while ((entity = media_graph_walk_next(&graph))) {
                struct xvip_dma *dma;

                if (entity->function != MEDIA_ENT_F_IO_V4L)
                        continue;

                dma = to_xvip_dma(media_entity_to_video_device(entity));

                if (dma->pad.flags & MEDIA_PAD_FL_SINK) {
                        pipe->output = dma;
                        num_outputs++;
                } else {
                        num_inputs++;
                }
        }

        mutex_unlock(&mdev->graph_mutex);

        media_graph_walk_cleanup(&graph);

        /* We need exactly one output and zero or one input. */
        if (num_outputs != 1 || num_inputs > 1)
                return -EPIPE;

        pipe->num_dmas = num_inputs + num_outputs;

        return 0;
}

static void __xvip_pipeline_cleanup(struct xvip_pipeline *pipe)
{
        pipe->num_dmas = 0;
        pipe->output = NULL;
}

/**
 * xvip_pipeline_cleanup - Cleanup the pipeline after streaming
 * @pipe: the pipeline
 *
 * Decrease the pipeline use count and clean it up if we were the last user.
 */
static void xvip_pipeline_cleanup(struct xvip_pipeline *pipe)
{
        mutex_lock(&pipe->lock);

        /* If we're the last user clean up the pipeline. */
        if (--pipe->use_count == 0)
                __xvip_pipeline_cleanup(pipe);

        mutex_unlock(&pipe->lock);
}

/**
 * xvip_pipeline_prepare - Prepare the pipeline for streaming
 * @pipe: the pipeline
 * @dma: DMA engine at one end of the pipeline
 *
 * Validate the pipeline if no user exists yet, otherwise just increase the use
 * count.
 *
 * Return: 0 if successful or -EPIPE if the pipeline is not valid.
 */
static int xvip_pipeline_prepare(struct xvip_pipeline *pipe,
                                 struct xvip_dma *dma)
{
        int ret;

        mutex_lock(&pipe->lock);

        /* If we're the first user validate and initialize the pipeline. */
        if (pipe->use_count == 0) {
                ret = xvip_pipeline_validate(pipe, dma);
                if (ret < 0) {
                        __xvip_pipeline_cleanup(pipe);
                        goto done;
                }
        }

        pipe->use_count++;
        ret = 0;

done:
        mutex_unlock(&pipe->lock);
        return ret;
}

/* -----------------------------------------------------------------------------
 * videobuf2 queue operations
 */

/**
 * struct xvip_dma_buffer - Video DMA buffer
 * @buf: vb2 buffer base object
 * @queue: buffer list entry in the DMA engine queued buffers list
 * @dma: DMA channel that uses the buffer
 */
struct xvip_dma_buffer {
        struct vb2_v4l2_buffer buf;
        struct list_head queue;
        struct xvip_dma *dma;
};

#define to_xvip_dma_buffer(vb)  container_of(vb, struct xvip_dma_buffer, buf)

static void xvip_dma_complete(void *param)
{
        struct xvip_dma_buffer *buf = param;
        struct xvip_dma *dma = buf->dma;

        spin_lock(&dma->queued_lock);
        list_del(&buf->queue);
        spin_unlock(&dma->queued_lock);

        buf->buf.field = V4L2_FIELD_NONE;
        buf->buf.sequence = dma->sequence++;
        buf->buf.vb2_buf.timestamp = ktime_get_ns();
        vb2_set_plane_payload(&buf->buf.vb2_buf, 0, dma->format.sizeimage);
        vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_DONE);
}

static int
xvip_dma_queue_setup(struct vb2_queue *vq,
                     unsigned int *nbuffers, unsigned int *nplanes,
                     unsigned int sizes[], struct device *alloc_devs[])
{
        struct xvip_dma *dma = vb2_get_drv_priv(vq);

        /* Make sure the image size is large enough. */
        if (*nplanes)
                return sizes[0] < dma->format.sizeimage ? -EINVAL : 0;

        *nplanes = 1;
        sizes[0] = dma->format.sizeimage;

        return 0;
}

static int xvip_dma_buffer_prepare(struct vb2_buffer *vb)
{
        struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
        struct xvip_dma *dma = vb2_get_drv_priv(vb->vb2_queue);
        struct xvip_dma_buffer *buf = to_xvip_dma_buffer(vbuf);

        buf->dma = dma;

        return 0;
}

static void xvip_dma_buffer_queue(struct vb2_buffer *vb)
{
        struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
        struct xvip_dma *dma = vb2_get_drv_priv(vb->vb2_queue);
        struct xvip_dma_buffer *buf = to_xvip_dma_buffer(vbuf);
        struct dma_async_tx_descriptor *desc;
        dma_addr_t addr = vb2_dma_contig_plane_dma_addr(vb, 0);
        u32 flags;

        if (dma->queue.type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
                flags = DMA_PREP_INTERRUPT | DMA_CTRL_ACK;
                dma->xt.dir = DMA_DEV_TO_MEM;
                dma->xt.src_sgl = false;
                dma->xt.dst_sgl = true;
                dma->xt.dst_start = addr;
        } else {
                flags = DMA_PREP_INTERRUPT | DMA_CTRL_ACK;
                dma->xt.dir = DMA_MEM_TO_DEV;
                dma->xt.src_sgl = true;
                dma->xt.dst_sgl = false;
                dma->xt.src_start = addr;
        }

        dma->xt.frame_size = 1;
        dma->sgl[0].size = dma->format.width * dma->fmtinfo->bpp;
        dma->sgl[0].icg = dma->format.bytesperline - dma->sgl[0].size;
        dma->xt.numf = dma->format.height;

        desc = dmaengine_prep_interleaved_dma(dma->dma, &dma->xt, flags);
        if (!desc) {
                dev_err(dma->xdev->dev, "Failed to prepare DMA transfer\n");
                vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_ERROR);
                return;
        }
        desc->callback = xvip_dma_complete;
        desc->callback_param = buf;

        spin_lock_irq(&dma->queued_lock);
        list_add_tail(&buf->queue, &dma->queued_bufs);
        spin_unlock_irq(&dma->queued_lock);

        dmaengine_submit(desc);

        if (vb2_is_streaming(&dma->queue))
                dma_async_issue_pending(dma->dma);
}

static int xvip_dma_start_streaming(struct vb2_queue *vq, unsigned int count)
{
        struct xvip_dma *dma = vb2_get_drv_priv(vq);
        struct xvip_dma_buffer *buf, *nbuf;
        struct xvip_pipeline *pipe;
        int ret;

        dma->sequence = 0;

        /*
         * Start streaming on the pipeline. No link touching an entity in the
         * pipeline can be activated or deactivated once streaming is started.
         *
         * Use the pipeline object embedded in the first DMA object that starts
         * streaming.
         */
        pipe = dma->video.entity.pipe
             ? to_xvip_pipeline(&dma->video.entity) : &dma->pipe;

        ret = media_pipeline_start(&dma->video.entity, &pipe->pipe);
        if (ret < 0)
                goto error;

        /* Verify that the configured format matches the output of the
         * connected subdev.
         */
        ret = xvip_dma_verify_format(dma);
        if (ret < 0)
                goto error_stop;

        ret = xvip_pipeline_prepare(pipe, dma);
        if (ret < 0)
                goto error_stop;

        /* Start the DMA engine. This must be done before starting the blocks
         * in the pipeline to avoid DMA synchronization issues.
         */
        dma_async_issue_pending(dma->dma);

        /* Start the pipeline. */
        xvip_pipeline_set_stream(pipe, true);

        return 0;

error_stop:
        media_pipeline_stop(&dma->video.entity);

error:
        /* Give back all queued buffers to videobuf2. */
        spin_lock_irq(&dma->queued_lock);
        list_for_each_entry_safe(buf, nbuf, &dma->queued_bufs, queue) {
                vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_QUEUED);
                list_del(&buf->queue);
        }
        spin_unlock_irq(&dma->queued_lock);

        return ret;
}

static void xvip_dma_stop_streaming(struct vb2_queue *vq)
{
        struct xvip_dma *dma = vb2_get_drv_priv(vq);
        struct xvip_pipeline *pipe = to_xvip_pipeline(&dma->video.entity);
        struct xvip_dma_buffer *buf, *nbuf;

        /* Stop the pipeline. */
        xvip_pipeline_set_stream(pipe, false);

        /* Stop and reset the DMA engine. */
        dmaengine_terminate_all(dma->dma);

        /* Cleanup the pipeline and mark it as being stopped. */
        xvip_pipeline_cleanup(pipe);
        media_pipeline_stop(&dma->video.entity);

        /* Give back all queued buffers to videobuf2. */
        spin_lock_irq(&dma->queued_lock);
        list_for_each_entry_safe(buf, nbuf, &dma->queued_bufs, queue) {
                vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_ERROR);
                list_del(&buf->queue);
        }
        spin_unlock_irq(&dma->queued_lock);
}

static const struct vb2_ops xvip_dma_queue_qops = {
        .queue_setup = xvip_dma_queue_setup,
        .buf_prepare = xvip_dma_buffer_prepare,
        .buf_queue = xvip_dma_buffer_queue,
        .wait_prepare = vb2_ops_wait_prepare,
        .wait_finish = vb2_ops_wait_finish,
        .start_streaming = xvip_dma_start_streaming,
        .stop_streaming = xvip_dma_stop_streaming,
};

/* -----------------------------------------------------------------------------
 * V4L2 ioctls
 */

static int
xvip_dma_querycap(struct file *file, void *fh, struct v4l2_capability *cap)
{
        struct v4l2_fh *vfh = file->private_data;
        struct xvip_dma *dma = to_xvip_dma(vfh->vdev);

        cap->capabilities = dma->xdev->v4l2_caps | V4L2_CAP_STREAMING |
                            V4L2_CAP_DEVICE_CAPS;

        strscpy(cap->driver, "xilinx-vipp", sizeof(cap->driver));
        strscpy(cap->card, dma->video.name, sizeof(cap->card));
        snprintf(cap->bus_info, sizeof(cap->bus_info), "platform:%pOFn:%u",
                 dma->xdev->dev->of_node, dma->port);

        return 0;
}

/* FIXME: without this callback function, some applications are not configured
 * with correct formats, and it results in frames in wrong format. Whether this
 * callback needs to be required is not clearly defined, so it should be
 * clarified through the mailing list.
 */
static int
xvip_dma_enum_format(struct file *file, void *fh, struct v4l2_fmtdesc *f)
{
        struct v4l2_fh *vfh = file->private_data;
        struct xvip_dma *dma = to_xvip_dma(vfh->vdev);

        if (f->index > 0)
                return -EINVAL;

        f->pixelformat = dma->format.pixelformat;

        return 0;
}

static int
xvip_dma_get_format(struct file *file, void *fh, struct v4l2_format *format)
{
        struct v4l2_fh *vfh = file->private_data;
        struct xvip_dma *dma = to_xvip_dma(vfh->vdev);

        format->fmt.pix = dma->format;

        return 0;
}

static void
__xvip_dma_try_format(struct xvip_dma *dma, struct v4l2_pix_format *pix,
                      const struct xvip_video_format **fmtinfo)
{
        const struct xvip_video_format *info;
        unsigned int min_width;
        unsigned int max_width;
        unsigned int min_bpl;
        unsigned int max_bpl;
        unsigned int width;
        unsigned int align;
        unsigned int bpl;

        /* Retrieve format information and select the default format if the
         * requested format isn't supported.
         */
        info = xvip_get_format_by_fourcc(pix->pixelformat);
        if (IS_ERR(info))
                info = xvip_get_format_by_fourcc(XVIP_DMA_DEF_FORMAT);

        pix->pixelformat = info->fourcc;
        pix->field = V4L2_FIELD_NONE;

        /* The transfer alignment requirements are expressed in bytes. Compute
         * the minimum and maximum values, clamp the requested width and convert
         * it back to pixels.
         */
        align = lcm(dma->align, info->bpp);
        min_width = roundup(XVIP_DMA_MIN_WIDTH, align);
        max_width = rounddown(XVIP_DMA_MAX_WIDTH, align);
        width = rounddown(pix->width * info->bpp, align);

        pix->width = clamp(width, min_width, max_width) / info->bpp;
        pix->height = clamp(pix->height, XVIP_DMA_MIN_HEIGHT,
                            XVIP_DMA_MAX_HEIGHT);

        /* Clamp the requested bytes per line value. If the maximum bytes per
         * line value is zero, the module doesn't support user configurable line
         * sizes. Override the requested value with the minimum in that case.
         */
        min_bpl = pix->width * info->bpp;
        max_bpl = rounddown(XVIP_DMA_MAX_WIDTH, dma->align);
        bpl = rounddown(pix->bytesperline, dma->align);

        pix->bytesperline = clamp(bpl, min_bpl, max_bpl);
        pix->sizeimage = pix->bytesperline * pix->height;

        if (fmtinfo)
                *fmtinfo = info;
}

static int
xvip_dma_try_format(struct file *file, void *fh, struct v4l2_format *format)
{
        struct v4l2_fh *vfh = file->private_data;
        struct xvip_dma *dma = to_xvip_dma(vfh->vdev);

        __xvip_dma_try_format(dma, &format->fmt.pix, NULL);
        return 0;
}

static int
xvip_dma_set_format(struct file *file, void *fh, struct v4l2_format *format)
{
        struct v4l2_fh *vfh = file->private_data;
        struct xvip_dma *dma = to_xvip_dma(vfh->vdev);
        const struct xvip_video_format *info;

        __xvip_dma_try_format(dma, &format->fmt.pix, &info);

        if (vb2_is_busy(&dma->queue))
                return -EBUSY;

        dma->format = format->fmt.pix;
        dma->fmtinfo = info;

        return 0;
}

static const struct v4l2_ioctl_ops xvip_dma_ioctl_ops = {
        .vidioc_querycap                = xvip_dma_querycap,
        .vidioc_enum_fmt_vid_cap        = xvip_dma_enum_format,
        .vidioc_g_fmt_vid_cap           = xvip_dma_get_format,
        .vidioc_g_fmt_vid_out           = xvip_dma_get_format,
        .vidioc_s_fmt_vid_cap           = xvip_dma_set_format,
        .vidioc_s_fmt_vid_out           = xvip_dma_set_format,
        .vidioc_try_fmt_vid_cap         = xvip_dma_try_format,
        .vidioc_try_fmt_vid_out         = xvip_dma_try_format,
        .vidioc_reqbufs                 = vb2_ioctl_reqbufs,
        .vidioc_querybuf                = vb2_ioctl_querybuf,
        .vidioc_qbuf                    = vb2_ioctl_qbuf,
        .vidioc_dqbuf                   = vb2_ioctl_dqbuf,
        .vidioc_create_bufs             = vb2_ioctl_create_bufs,
        .vidioc_expbuf                  = vb2_ioctl_expbuf,
        .vidioc_streamon                = vb2_ioctl_streamon,
        .vidioc_streamoff               = vb2_ioctl_streamoff,
};

/* -----------------------------------------------------------------------------
 * V4L2 file operations
 */

static const struct v4l2_file_operations xvip_dma_fops = {
        .owner          = THIS_MODULE,
        .unlocked_ioctl = video_ioctl2,
        .open           = v4l2_fh_open,
        .release        = vb2_fop_release,
        .poll           = vb2_fop_poll,
        .mmap           = vb2_fop_mmap,
};

/* -----------------------------------------------------------------------------
 * Xilinx Video DMA Core
 */

int xvip_dma_init(struct xvip_composite_device *xdev, struct xvip_dma *dma,
                  enum v4l2_buf_type type, unsigned int port)
{
        char name[16];
        int ret;

        dma->xdev = xdev;
        dma->port = port;
        mutex_init(&dma->lock);
        mutex_init(&dma->pipe.lock);
        INIT_LIST_HEAD(&dma->queued_bufs);
        spin_lock_init(&dma->queued_lock);

        dma->fmtinfo = xvip_get_format_by_fourcc(XVIP_DMA_DEF_FORMAT);
        dma->format.pixelformat = dma->fmtinfo->fourcc;
        dma->format.colorspace = V4L2_COLORSPACE_SRGB;
        dma->format.field = V4L2_FIELD_NONE;
        dma->format.width = XVIP_DMA_DEF_WIDTH;
        dma->format.height = XVIP_DMA_DEF_HEIGHT;
        dma->format.bytesperline = dma->format.width * dma->fmtinfo->bpp;
        dma->format.sizeimage = dma->format.bytesperline * dma->format.height;

        /* Initialize the media entity... */
        dma->pad.flags = type == V4L2_BUF_TYPE_VIDEO_CAPTURE
                       ? MEDIA_PAD_FL_SINK : MEDIA_PAD_FL_SOURCE;

        ret = media_entity_pads_init(&dma->video.entity, 1, &dma->pad);
        if (ret < 0)
                goto error;

        /* ... and the video node... */
        dma->video.fops = &xvip_dma_fops;
        dma->video.v4l2_dev = &xdev->v4l2_dev;
        dma->video.queue = &dma->queue;
        snprintf(dma->video.name, sizeof(dma->video.name), "%pOFn %s %u",
                 xdev->dev->of_node,
                 type == V4L2_BUF_TYPE_VIDEO_CAPTURE ? "output" : "input",
                 port);
        dma->video.vfl_type = VFL_TYPE_VIDEO;
        dma->video.vfl_dir = type == V4L2_BUF_TYPE_VIDEO_CAPTURE
                           ? VFL_DIR_RX : VFL_DIR_TX;
        dma->video.release = video_device_release_empty;
        dma->video.ioctl_ops = &xvip_dma_ioctl_ops;
        dma->video.lock = &dma->lock;
        dma->video.device_caps = V4L2_CAP_STREAMING;
        if (type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
                dma->video.device_caps |= V4L2_CAP_VIDEO_CAPTURE;
        else
                dma->video.device_caps |= V4L2_CAP_VIDEO_OUTPUT;

        video_set_drvdata(&dma->video, dma);

        /* ... and the buffers queue... */
        /* Don't enable VB2_READ and VB2_WRITE, as using the read() and write()
         * V4L2 APIs would be inefficient. Testing on the command line with a
         * 'cat /dev/video?' thus won't be possible, but given that the driver
         * anyway requires a test tool to setup the pipeline before any video
         * stream can be started, requiring a specific V4L2 test tool as well
         * instead of 'cat' isn't really a drawback.
         */
        dma->queue.type = type;
        dma->queue.io_modes = VB2_MMAP | VB2_USERPTR | VB2_DMABUF;
        dma->queue.lock = &dma->lock;
        dma->queue.drv_priv = dma;
        dma->queue.buf_struct_size = sizeof(struct xvip_dma_buffer);
        dma->queue.ops = &xvip_dma_queue_qops;
        dma->queue.mem_ops = &vb2_dma_contig_memops;
        dma->queue.timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC
                                   | V4L2_BUF_FLAG_TSTAMP_SRC_EOF;
        dma->queue.dev = dma->xdev->dev;
        ret = vb2_queue_init(&dma->queue);
        if (ret < 0) {
                dev_err(dma->xdev->dev, "failed to initialize VB2 queue\n");
                goto error;
        }

        /* ... and the DMA channel. */
        snprintf(name, sizeof(name), "port%u", port);
        dma->dma = dma_request_chan(dma->xdev->dev, name);
        if (IS_ERR(dma->dma)) {
                ret = PTR_ERR(dma->dma);
                if (ret != -EPROBE_DEFER)
                        dev_err(dma->xdev->dev, "no VDMA channel found\n");
                goto error;
        }

        dma->align = 1 << dma->dma->device->copy_align;

        ret = video_register_device(&dma->video, VFL_TYPE_VIDEO, -1);
        if (ret < 0) {
                dev_err(dma->xdev->dev, "failed to register video device\n");
                goto error;
        }

        return 0;

error:
        xvip_dma_cleanup(dma);
        return ret;
}

void xvip_dma_cleanup(struct xvip_dma *dma)
{
        if (video_is_registered(&dma->video))
                video_unregister_device(&dma->video);

        if (!IS_ERR_OR_NULL(dma->dma))
                dma_release_channel(dma->dma);

        media_entity_cleanup(&dma->video.entity);

        mutex_destroy(&dma->lock);
        mutex_destroy(&dma->pipe.lock);
}