daedalus-v4l2/kernel/daedalus_v4l2_main.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * daedalus-v4l2 — V4L2 stateless decoder shim.
 *
 * Out-of-tree Linux kernel module that exposes a /dev/videoNN
 * V4L2 device for the daedalus-fourier kernel library.  Real
 * decoding work happens in a userspace daemon (this module
 * forwards bitstream + stateless-codec control structs via a
 * chardev bridge — that part lands in Phase 8.2).
 *
 * Phase 8.1 (this commit): minimal viable skeleton.  Registers a
 * platform device + v4l2_device + video_device and answers
 * VIDIOC_QUERYCAP with reasonable values.  Other ioctls fall
 * through to v4l2-core defaults; modprobe / rmmod is a clean
 * round-trip.
 *
 * Project: https://git.reauktion.de/reauktion/daedalus-v4l2
 * Sibling kernel library: https://git.reauktion.de/marfrit/daedalus-fourier
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#include <media/v4l2-device.h>
#include <media/v4l2-dev.h>
#include <media/v4l2-ioctl.h>

#define DAEDALUS_DRV_NAME	"daedalus_v4l2"
#define DAEDALUS_VIDEO_NAME	"daedalus"

/**
 * struct daedalus_dev - top-level device state
 * @pdev:	owning platform device (synthesised in module_init)
 * @v4l2_dev:	V4L2 device parent for any video_device we register
 * @vdev:	video_device exposed as /dev/videoNN
 *
 * One-instance singleton for Phase 8.1.  Multi-instance support
 * (one decoder per /dev/videoNN) lands when m2m wiring goes in.
 */
struct daedalus_dev {
	struct platform_device	*pdev;
	struct v4l2_device	v4l2_dev;
	struct video_device	vdev;
};

/*
 * V4L2 ioctl dispatch table.  Phase 8.1 only implements
 * VIDIOC_QUERYCAP; everything else returns -ENOTTY via the
 * v4l2-core's default handler when the op is NULL.
 */
static int daedalus_querycap(struct file *file, void *priv,
			     struct v4l2_capability *cap)
{
	strscpy(cap->driver, DAEDALUS_DRV_NAME, sizeof(cap->driver));
	/*
	 * cap->card is 32 bytes incl. NUL terminator.  Pick a name
	 * that fits without truncation.
	 */
	strscpy(cap->card, "daedalus-fourier V3D7+NEON",
		sizeof(cap->card));
	snprintf(cap->bus_info, sizeof(cap->bus_info),
		 "platform:%s", DAEDALUS_DRV_NAME);
	return 0;
}

static const struct v4l2_ioctl_ops daedalus_ioctl_ops = {
	.vidioc_querycap = daedalus_querycap,
	/*
	 * Phase 8.2+ adds:
	 *   .vidioc_enum_fmt_vid_{cap,out}_mplane
	 *   .vidioc_g/s_fmt_vid_{cap,out}_mplane
	 *   .vidioc_reqbufs / vidioc_{q,dq,query}buf
	 *   .vidioc_streamon / .vidioc_streamoff
	 *   stateless-codec controls via the v4l2_ctrl_handler.
	 */
};

/*
 * Phase 8.1 placeholder for .release.  We DON'T yet have a
 * vb2_queue (that's Phase 8.2), so the real vb2_fop_release
 * isn't usable.  Use the minimal v4l2_fh_release for now; the
 * Phase 8.2 patch swaps this for vb2_fop_release.
 */
static int daedalus_release_phase81(struct file *file)
{
	return v4l2_fh_release(file);
}

/*
 * File operations.  v4l2_fh_open provides the default open the
 * v4l2-core machinery expects; .release is our Phase 8.1
 * placeholder; .unlocked_ioctl uses the kernel's video_ioctl2
 * dispatcher against our v4l2_ioctl_ops table.
 */
static const struct v4l2_file_operations daedalus_fops = {
	.owner		= THIS_MODULE,
	.open		= v4l2_fh_open,
	.release	= daedalus_release_phase81,
	.unlocked_ioctl	= video_ioctl2,
};

static void daedalus_vdev_release(struct video_device *vdev)
{
	/*
	 * The video_device is embedded inside our daedalus_dev which
	 * lives as long as the platform_device.  Nothing to free here
	 * directly; this no-op release just satisfies v4l2-core's
	 * requirement that .release be set.
	 */
}

static int daedalus_probe(struct platform_device *pdev)
{
	struct daedalus_dev *dev;
	int ret;

	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return -ENOMEM;
	dev->pdev = pdev;
	platform_set_drvdata(pdev, dev);

	ret = v4l2_device_register(&pdev->dev, &dev->v4l2_dev);
	if (ret) {
		dev_err(&pdev->dev, "v4l2_device_register: %d\n", ret);
		return ret;
	}

	/* Set up video_device.  Embedded; vdev->release is no-op. */
	strscpy(dev->vdev.name, DAEDALUS_VIDEO_NAME, sizeof(dev->vdev.name));
	dev->vdev.fops = &daedalus_fops;
	dev->vdev.ioctl_ops = &daedalus_ioctl_ops;
	dev->vdev.release = daedalus_vdev_release;
	dev->vdev.v4l2_dev = &dev->v4l2_dev;
	dev->vdev.vfl_dir = VFL_DIR_M2M;          /* mem2mem: bitstream in, frames out */
	dev->vdev.device_caps = V4L2_CAP_VIDEO_M2M_MPLANE
				  | V4L2_CAP_STREAMING;
	video_set_drvdata(&dev->vdev, dev);

	ret = video_register_device(&dev->vdev, VFL_TYPE_VIDEO, -1);
	if (ret) {
		dev_err(&pdev->dev, "video_register_device: %d\n", ret);
		v4l2_device_unregister(&dev->v4l2_dev);
		return ret;
	}

	v4l2_info(&dev->v4l2_dev,
		  "daedalus-v4l2 registered as /dev/video%d (Phase 8.1 skeleton)\n",
		  dev->vdev.num);

	return 0;
}

static void daedalus_remove(struct platform_device *pdev)
{
	struct daedalus_dev *dev = platform_get_drvdata(pdev);

	video_unregister_device(&dev->vdev);
	v4l2_device_unregister(&dev->v4l2_dev);
}

static struct platform_driver daedalus_platform_driver = {
	.probe	= daedalus_probe,
	.remove	= daedalus_remove,
	.driver	= {
		.name = DAEDALUS_DRV_NAME,
	},
};

/*
 * The platform device that our driver binds to.  Synthesised
 * at module load time since we have no device tree node yet
 * (out-of-tree module; not vendored into the rpi DT).
 */
static struct platform_device *daedalus_platform_device;

static int __init daedalus_init(void)
{
	int ret;

	daedalus_platform_device = platform_device_alloc(DAEDALUS_DRV_NAME, -1);
	if (!daedalus_platform_device)
		return -ENOMEM;

	ret = platform_device_add(daedalus_platform_device);
	if (ret) {
		platform_device_put(daedalus_platform_device);
		return ret;
	}

	ret = platform_driver_register(&daedalus_platform_driver);
	if (ret) {
		platform_device_unregister(daedalus_platform_device);
		return ret;
	}

	return 0;
}

static void __exit daedalus_exit(void)
{
	platform_driver_unregister(&daedalus_platform_driver);
	platform_device_unregister(daedalus_platform_device);
}

module_init(daedalus_init);
module_exit(daedalus_exit);

MODULE_AUTHOR("Markus Fritsche <fritsche.markus@gmail.com>");
MODULE_DESCRIPTION("V4L2 stateless decoder shim for daedalus-fourier (Pi 5 / VC7)");
MODULE_LICENSE("GPL v2");
MODULE_VERSION("0.0.1");