[media] v4l2-pci-skeleton: add a V4L2 PCI skeleton driver

This example driver uses all the latest frameworks and can serve as a
starting point for a new V4L2 PCI driver.

Originally written for a presentation on how to use V4L2 frameworks
during FOSDEM 2014.

Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

Documentation/video4linux/v4l2-framework.txt

···
 need and this same framework should make it much easier to refactor
 common code into utility functions shared by all drivers.
 
+A good example to look at as a reference is the v4l2-pci-skeleton.c
+source that is available in this directory. It is a skeleton driver for
+a PCI capture card, and demonstrates how to use the V4L2 driver
+framework. It can be used as a template for real PCI video capture driver.
 
 Structure of a driver
 ---------------------

Documentation/video4linux/v4l2-pci-skeleton.c

···
+/*
+ * This is a V4L2 PCI Skeleton Driver. It gives an initial skeleton source
+ * for use with other PCI drivers.
+ *
+ * This skeleton PCI driver assumes that the card has an S-Video connector as
+ * input 0 and an HDMI connector as input 1.
+ *
+ * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kmod.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/interrupt.h>
+#include <linux/videodev2.h>
+#include <linux/v4l2-dv-timings.h>
+#include <media/v4l2-device.h>
+#include <media/v4l2-dev.h>
+#include <media/v4l2-ioctl.h>
+#include <media/v4l2-dv-timings.h>
+#include <media/v4l2-ctrls.h>
+#include <media/v4l2-event.h>
+#include <media/videobuf2-dma-contig.h>
+
+MODULE_DESCRIPTION("V4L2 PCI Skeleton Driver");
+MODULE_AUTHOR("Hans Verkuil");
+MODULE_LICENSE("GPL v2");
+MODULE_DEVICE_TABLE(pci, skeleton_pci_tbl);
+
+/**
+ * struct skeleton - All internal data for one instance of device
+ * @pdev: PCI device
+ * @v4l2_dev: top-level v4l2 device struct
+ * @vdev: video node structure
+ * @ctrl_handler: control handler structure
+ * @lock: ioctl serialization mutex
+ * @std: current SDTV standard
+ * @timings: current HDTV timings
+ * @format: current pix format
+ * @input: current video input (0 = SDTV, 1 = HDTV)
+ * @queue: vb2 video capture queue
+ * @alloc_ctx: vb2 contiguous DMA context
+ * @qlock: spinlock controlling access to buf_list and sequence
+ * @buf_list: list of buffers queued for DMA
+ * @sequence: frame sequence counter
+ */
+struct skeleton {
+	struct pci_dev *pdev;
+	struct v4l2_device v4l2_dev;
+	struct video_device vdev;
+	struct v4l2_ctrl_handler ctrl_handler;
+	struct mutex lock;
+	v4l2_std_id std;
+	struct v4l2_dv_timings timings;
+	struct v4l2_pix_format format;
+	unsigned input;
+
+	struct vb2_queue queue;
+	struct vb2_alloc_ctx *alloc_ctx;
+
+	spinlock_t qlock;
+	struct list_head buf_list;
+	unsigned int sequence;
+};
+
+struct skel_buffer {
+	struct vb2_buffer vb;
+	struct list_head list;
+};
+
+static inline struct skel_buffer *to_skel_buffer(struct vb2_buffer *vb2)
+{
+	return container_of(vb2, struct skel_buffer, vb);
+}
+
+static const struct pci_device_id skeleton_pci_tbl[] = {
+	/* { PCI_DEVICE(PCI_VENDOR_ID_, PCI_DEVICE_ID_) }, */
+	{ 0, }
+};
+
+/*
+ * HDTV: this structure has the capabilities of the HDTV receiver.
+ * It is used to constrain the huge list of possible formats based
+ * upon the hardware capabilities.
+ */
+static const struct v4l2_dv_timings_cap skel_timings_cap = {
+	.type = V4L2_DV_BT_656_1120,
+	/* keep this initialization for compatibility with GCC < 4.4.6 */
+	.reserved = { 0 },
+	V4L2_INIT_BT_TIMINGS(
+		720, 1920,		/* min/max width */
+		480, 1080,		/* min/max height */
+		27000000, 74250000,	/* min/max pixelclock*/
+		V4L2_DV_BT_STD_CEA861,	/* Supported standards */
+		/* capabilities */
+		V4L2_DV_BT_CAP_INTERLACED | V4L2_DV_BT_CAP_PROGRESSIVE
+	)
+};
+
+/*
+ * Supported SDTV standards. This does the same job as skel_timings_cap, but
+ * for standard TV formats.
+ */
+#define SKEL_TVNORMS V4L2_STD_ALL
+
+/*
+ * Interrupt handler: typically interrupts happen after a new frame has been
+ * captured. It is the job of the handler to remove the new frame from the
+ * internal list and give it back to the vb2 framework, updating the sequence
+ * counter and timestamp at the same time.
+ */
+static irqreturn_t skeleton_irq(int irq, void *dev_id)
+{
+#ifdef TODO
+	struct skeleton *skel = dev_id;
+
+	/* handle interrupt */
+
+	/* Once a new frame has been captured, mark it as done like this: */
+	if (captured_new_frame) {
+		...
+		spin_lock(&skel->qlock);
+		list_del(&new_buf->list);
+		spin_unlock(&skel->qlock);
+		new_buf->vb.v4l2_buf.sequence = skel->sequence++;
+		v4l2_get_timestamp(&new_buf->vb.v4l2_buf.timestamp);
+		vb2_buffer_done(&new_buf->vb, VB2_BUF_STATE_DONE);
+	}
+#endif
+	return IRQ_HANDLED;
+}
+
+/*
+ * Setup the constraints of the queue: besides setting the number of planes
+ * per buffer and the size and allocation context of each plane, it also
+ * checks if sufficient buffers have been allocated. Usually 3 is a good
+ * minimum number: many DMA engines need a minimum of 2 buffers in the
+ * queue and you need to have another available for userspace processing.
+ */
+static int queue_setup(struct vb2_queue *vq, const struct v4l2_format *fmt,
+		       unsigned int *nbuffers, unsigned int *nplanes,
+		       unsigned int sizes[], void *alloc_ctxs[])
+{
+	struct skeleton *skel = vb2_get_drv_priv(vq);
+
+	if (vq->num_buffers + *nbuffers < 3)
+		*nbuffers = 3 - vq->num_buffers;
+
+	if (fmt && fmt->fmt.pix.sizeimage < skel->format.sizeimage)
+		return -EINVAL;
+	*nplanes = 1;
+	sizes[0] = fmt ? fmt->fmt.pix.sizeimage : skel->format.sizeimage;
+	alloc_ctxs[0] = skel->alloc_ctx;
+	return 0;
+}
+
+/*
+ * Prepare the buffer for queueing to the DMA engine: check and set the
+ * payload size and fill in the field. Note: if the format's field is
+ * V4L2_FIELD_ALTERNATE, then vb->v4l2_buf.field should be set in the
+ * interrupt handler since that's usually where you know if the TOP or
+ * BOTTOM field has been captured.
+ */
+static int buffer_prepare(struct vb2_buffer *vb)
+{
+	struct skeleton *skel = vb2_get_drv_priv(vb->vb2_queue);
+	unsigned long size = skel->format.sizeimage;
+
+	if (vb2_plane_size(vb, 0) < size) {
+		dev_err(&skel->pdev->dev, "buffer too small (%lu < %lu)\n",
+			 vb2_plane_size(vb, 0), size);
+		return -EINVAL;
+	}
+
+	vb2_set_plane_payload(vb, 0, size);
+	vb->v4l2_buf.field = skel->format.field;
+	return 0;
+}
+
+/*
+ * Queue this buffer to the DMA engine.
+ */
+static void buffer_queue(struct vb2_buffer *vb)
+{
+	struct skeleton *skel = vb2_get_drv_priv(vb->vb2_queue);
+	struct skel_buffer *buf = to_skel_buffer(vb);
+	unsigned long flags;
+
+	spin_lock_irqsave(&skel->qlock, flags);
+	list_add_tail(&buf->list, &skel->buf_list);
+
+	/* TODO: Update any DMA pointers if necessary */
+
+	spin_unlock_irqrestore(&skel->qlock, flags);
+}
+
+static void return_all_buffers(struct skeleton *skel,
+			       enum vb2_buffer_state state)
+{
+	struct skel_buffer *buf, *node;
+	unsigned long flags;
+
+	spin_lock_irqsave(&skel->qlock, flags);
+	list_for_each_entry_safe(buf, node, &skel->buf_list, list) {
+		vb2_buffer_done(&buf->vb, state);
+		list_del(&buf->list);
+	}
+	spin_unlock_irqrestore(&skel->qlock, flags);
+}
+
+/*
+ * Start streaming. First check if the minimum number of buffers have been
+ * queued. If not, then return -ENOBUFS and the vb2 framework will call
+ * this function again the next time a buffer has been queued until enough
+ * buffers are available to actually start the DMA engine.
+ */
+static int start_streaming(struct vb2_queue *vq, unsigned int count)
+{
+	struct skeleton *skel = vb2_get_drv_priv(vq);
+	int ret = 0;
+
+	skel->sequence = 0;
+
+	/* TODO: start DMA */
+
+	if (ret) {
+		/*
+		 * In case of an error, return all active buffers to the
+		 * QUEUED state
+		 */
+		return_all_buffers(skel, VB2_BUF_STATE_QUEUED);
+	}
+	return ret;
+}
+
+/*
+ * Stop the DMA engine. Any remaining buffers in the DMA queue are dequeued
+ * and passed on to the vb2 framework marked as STATE_ERROR.
+ */
+static int stop_streaming(struct vb2_queue *vq)
+{
+	struct skeleton *skel = vb2_get_drv_priv(vq);
+
+	/* TODO: stop DMA */
+
+	/* Release all active buffers */
+	return_all_buffers(skel, VB2_BUF_STATE_ERROR);
+	return 0;
+}
+
+/*
+ * The vb2 queue ops. Note that since q->lock is set we can use the standard
+ * vb2_ops_wait_prepare/finish helper functions. If q->lock would be NULL,
+ * then this driver would have to provide these ops.
+ */
+static struct vb2_ops skel_qops = {
+	.queue_setup		= queue_setup,
+	.buf_prepare		= buffer_prepare,
+	.buf_queue		= buffer_queue,
+	.start_streaming	= start_streaming,
+	.stop_streaming		= stop_streaming,
+	.wait_prepare		= vb2_ops_wait_prepare,
+	.wait_finish		= vb2_ops_wait_finish,
+};
+
+/*
+ * Required ioctl querycap. Note that the version field is prefilled with
+ * the version of the kernel.
+ */
+static int skeleton_querycap(struct file *file, void *priv,
+			     struct v4l2_capability *cap)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	strlcpy(cap->driver, KBUILD_MODNAME, sizeof(cap->driver));
+	strlcpy(cap->card, "V4L2 PCI Skeleton", sizeof(cap->card));
+	snprintf(cap->bus_info, sizeof(cap->bus_info), "PCI:%s",
+		 pci_name(skel->pdev));
+	cap->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_READWRITE |
+			   V4L2_CAP_STREAMING;
+	cap->capabilities = cap->device_caps | V4L2_CAP_DEVICE_CAPS;
+	return 0;
+}
+
+/*
+ * Helper function to check and correct struct v4l2_pix_format. It's used
+ * not only in VIDIOC_TRY/S_FMT, but also elsewhere if changes to the SDTV
+ * standard, HDTV timings or the video input would require updating the
+ * current format.
+ */
+static void skeleton_fill_pix_format(struct skeleton *skel,
+				     struct v4l2_pix_format *pix)
+{
+	pix->pixelformat = V4L2_PIX_FMT_YUYV;
+	if (skel->input == 0) {
+		/* S-Video input */
+		pix->width = 720;
+		pix->height = (skel->std & V4L2_STD_525_60) ? 480 : 576;
+		pix->field = V4L2_FIELD_INTERLACED;
+		pix->colorspace = V4L2_COLORSPACE_SMPTE170M;
+	} else {
+		/* HDMI input */
+		pix->width = skel->timings.bt.width;
+		pix->height = skel->timings.bt.height;
+		if (skel->timings.bt.interlaced)
+			pix->field = V4L2_FIELD_INTERLACED;
+		else
+			pix->field = V4L2_FIELD_NONE;
+		pix->colorspace = V4L2_COLORSPACE_REC709;
+	}
+
+	/*
+	 * The YUYV format is four bytes for every two pixels, so bytesperline
+	 * is width * 2.
+	 */
+	pix->bytesperline = pix->width * 2;
+	pix->sizeimage = pix->bytesperline * pix->height;
+	pix->priv = 0;
+}
+
+static int skeleton_try_fmt_vid_cap(struct file *file, void *priv,
+				    struct v4l2_format *f)
+{
+	struct skeleton *skel = video_drvdata(file);
+	struct v4l2_pix_format *pix = &f->fmt.pix;
+
+	/*
+	 * Due to historical reasons providing try_fmt with an unsupported
+	 * pixelformat will return -EINVAL for video receivers. Webcam drivers,
+	 * however, will silently correct the pixelformat. Some video capture
+	 * applications rely on this behavior...
+	 */
+	if (pix->pixelformat != V4L2_PIX_FMT_YUYV)
+		return -EINVAL;
+	skeleton_fill_pix_format(skel, pix);
+	return 0;
+}
+
+static int skeleton_s_fmt_vid_cap(struct file *file, void *priv,
+				  struct v4l2_format *f)
+{
+	struct skeleton *skel = video_drvdata(file);
+	int ret;
+
+	ret = skeleton_try_fmt_vid_cap(file, priv, f);
+	if (ret)
+		return ret;
+
+	/*
+	 * It is not allowed to change the format while buffers for use with
+	 * streaming have already been allocated.
+	 */
+	if (vb2_is_busy(&skel->queue))
+		return -EBUSY;
+
+	/* TODO: change format */
+	skel->format = f->fmt.pix;
+	return 0;
+}
+
+static int skeleton_g_fmt_vid_cap(struct file *file, void *priv,
+				  struct v4l2_format *f)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	f->fmt.pix = skel->format;
+	return 0;
+}
+
+static int skeleton_enum_fmt_vid_cap(struct file *file, void *priv,
+				     struct v4l2_fmtdesc *f)
+{
+	if (f->index != 0)
+		return -EINVAL;
+
+	strlcpy(f->description, "4:2:2, packed, YUYV", sizeof(f->description));
+	f->pixelformat = V4L2_PIX_FMT_YUYV;
+	f->flags = 0;
+	return 0;
+}
+
+static int skeleton_s_std(struct file *file, void *priv, v4l2_std_id std)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* S_STD is not supported on the HDMI input */
+	if (skel->input)
+		return -ENODATA;
+
+	/*
+	 * No change, so just return. Some applications call S_STD again after
+	 * the buffers for streaming have been set up, so we have to allow for
+	 * this behavior.
+	 */
+	if (std == skel->std)
+		return 0;
+
+	/*
+	 * Changing the standard implies a format change, which is not allowed
+	 * while buffers for use with streaming have already been allocated.
+	 */
+	if (vb2_is_busy(&skel->queue))
+		return -EBUSY;
+
+	/* TODO: handle changing std */
+
+	skel->std = std;
+
+	/* Update the internal format */
+	skeleton_fill_pix_format(skel, &skel->format);
+	return 0;
+}
+
+static int skeleton_g_std(struct file *file, void *priv, v4l2_std_id *std)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* G_STD is not supported on the HDMI input */
+	if (skel->input)
+		return -ENODATA;
+
+	*std = skel->std;
+	return 0;
+}
+
+/*
+ * Query the current standard as seen by the hardware. This function shall
+ * never actually change the standard, it just detects and reports.
+ * The framework will initially set *std to tvnorms (i.e. the set of
+ * supported standards by this input), and this function should just AND
+ * this value. If there is no signal, then *std should be set to 0.
+ */
+static int skeleton_querystd(struct file *file, void *priv, v4l2_std_id *std)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* QUERY_STD is not supported on the HDMI input */
+	if (skel->input)
+		return -ENODATA;
+
+#ifdef TODO
+	/*
+	 * Query currently seen standard. Initial value of *std is
+	 * V4L2_STD_ALL. This function should look something like this:
+	 */
+	get_signal_info();
+	if (no_signal) {
+		*std = 0;
+		return 0;
+	}
+	/* Use signal information to reduce the number of possible standards */
+	if (signal_has_525_lines)
+		*std &= V4L2_STD_525_60;
+	else
+		*std &= V4L2_STD_625_50;
+#endif
+	return 0;
+}
+
+static int skeleton_s_dv_timings(struct file *file, void *_fh,
+				 struct v4l2_dv_timings *timings)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* S_DV_TIMINGS is not supported on the S-Video input */
+	if (skel->input == 0)
+		return -ENODATA;
+
+	/* Quick sanity check */
+	if (!v4l2_valid_dv_timings(timings, &skel_timings_cap, NULL, NULL))
+		return -EINVAL;
+
+	/* Check if the timings are part of the CEA-861 timings. */
+	if (!v4l2_find_dv_timings_cap(timings, &skel_timings_cap,
+				      0, NULL, NULL))
+		return -EINVAL;
+
+	/* Return 0 if the new timings are the same as the current timings. */
+	if (v4l2_match_dv_timings(timings, &skel->timings, 0))
+		return 0;
+
+	/*
+	 * Changing the timings implies a format change, which is not allowed
+	 * while buffers for use with streaming have already been allocated.
+	 */
+	if (vb2_is_busy(&skel->queue))
+		return -EBUSY;
+
+	/* TODO: Configure new timings */
+
+	/* Save timings */
+	skel->timings = *timings;
+
+	/* Update the internal format */
+	skeleton_fill_pix_format(skel, &skel->format);
+	return 0;
+}
+
+static int skeleton_g_dv_timings(struct file *file, void *_fh,
+				 struct v4l2_dv_timings *timings)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* G_DV_TIMINGS is not supported on the S-Video input */
+	if (skel->input == 0)
+		return -ENODATA;
+
+	*timings = skel->timings;
+	return 0;
+}
+
+static int skeleton_enum_dv_timings(struct file *file, void *_fh,
+				    struct v4l2_enum_dv_timings *timings)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* ENUM_DV_TIMINGS is not supported on the S-Video input */
+	if (skel->input == 0)
+		return -ENODATA;
+
+	return v4l2_enum_dv_timings_cap(timings, &skel_timings_cap,
+					NULL, NULL);
+}
+
+/*
+ * Query the current timings as seen by the hardware. This function shall
+ * never actually change the timings, it just detects and reports.
+ * If no signal is detected, then return -ENOLINK. If the hardware cannot
+ * lock to the signal, then return -ENOLCK. If the signal is out of range
+ * of the capabilities of the system (e.g., it is possible that the receiver
+ * can lock but that the DMA engine it is connected to cannot handle
+ * pixelclocks above a certain frequency), then -ERANGE is returned.
+ */
+static int skeleton_query_dv_timings(struct file *file, void *_fh,
+				     struct v4l2_dv_timings *timings)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* QUERY_DV_TIMINGS is not supported on the S-Video input */
+	if (skel->input == 0)
+		return -ENODATA;
+
+#ifdef TODO
+	/*
+	 * Query currently seen timings. This function should look
+	 * something like this:
+	 */
+	detect_timings();
+	if (no_signal)
+		return -ENOLINK;
+	if (cannot_lock_to_signal)
+		return -ENOLCK;
+	if (signal_out_of_range_of_capabilities)
+		return -ERANGE;
+
+	/* Useful for debugging */
+	v4l2_print_dv_timings(skel->v4l2_dev.name, "query_dv_timings:",
+			timings, true);
+#endif
+	return 0;
+}
+
+static int skeleton_dv_timings_cap(struct file *file, void *fh,
+				   struct v4l2_dv_timings_cap *cap)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	/* DV_TIMINGS_CAP is not supported on the S-Video input */
+	if (skel->input == 0)
+		return -ENODATA;
+	*cap = skel_timings_cap;
+	return 0;
+}
+
+static int skeleton_enum_input(struct file *file, void *priv,
+			       struct v4l2_input *i)
+{
+	if (i->index > 1)
+		return -EINVAL;
+
+	i->type = V4L2_INPUT_TYPE_CAMERA;
+	if (i->index == 0) {
+		i->std = SKEL_TVNORMS;
+		strlcpy(i->name, "S-Video", sizeof(i->name));
+		i->capabilities = V4L2_IN_CAP_STD;
+	} else {
+		i->std = 0;
+		strlcpy(i->name, "HDMI", sizeof(i->name));
+		i->capabilities = V4L2_IN_CAP_DV_TIMINGS;
+	}
+	return 0;
+}
+
+static int skeleton_s_input(struct file *file, void *priv, unsigned int i)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	if (i > 1)
+		return -EINVAL;
+
+	/*
+	 * Changing the input implies a format change, which is not allowed
+	 * while buffers for use with streaming have already been allocated.
+	 */
+	if (vb2_is_busy(&skel->queue))
+		return -EBUSY;
+
+	skel->input = i;
+	/*
+	 * Update tvnorms. The tvnorms value is used by the core to implement
+	 * VIDIOC_ENUMSTD so it has to be correct. If tvnorms == 0, then
+	 * ENUMSTD will return -ENODATA.
+	 */
+	skel->vdev.tvnorms = i ? 0 : SKEL_TVNORMS;
+
+	/* Update the internal format */
+	skeleton_fill_pix_format(skel, &skel->format);
+	return 0;
+}
+
+static int skeleton_g_input(struct file *file, void *priv, unsigned int *i)
+{
+	struct skeleton *skel = video_drvdata(file);
+
+	*i = skel->input;
+	return 0;
+}
+
+/* The control handler. */
+static int skeleton_s_ctrl(struct v4l2_ctrl *ctrl)
+{
+	/*struct skeleton *skel =
+		container_of(ctrl->handler, struct skeleton, ctrl_handler);*/
+
+	switch (ctrl->id) {
+	case V4L2_CID_BRIGHTNESS:
+		/* TODO: set brightness to ctrl->val */
+		break;
+	case V4L2_CID_CONTRAST:
+		/* TODO: set contrast to ctrl->val */
+		break;
+	case V4L2_CID_SATURATION:
+		/* TODO: set saturation to ctrl->val */
+		break;
+	case V4L2_CID_HUE:
+		/* TODO: set hue to ctrl->val */
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+/* ------------------------------------------------------------------
+	File operations for the device
+   ------------------------------------------------------------------*/
+
+static const struct v4l2_ctrl_ops skel_ctrl_ops = {
+	.s_ctrl = skeleton_s_ctrl,
+};
+
+/*
+ * The set of all supported ioctls. Note that all the streaming ioctls
+ * use the vb2 helper functions that take care of all the locking and
+ * that also do ownership tracking (i.e. only the filehandle that requested
+ * the buffers can call the streaming ioctls, all other filehandles will
+ * receive -EBUSY if they attempt to call the same streaming ioctls).
+ *
+ * The last three ioctls also use standard helper functions: these implement
+ * standard behavior for drivers with controls.
+ */
+static const struct v4l2_ioctl_ops skel_ioctl_ops = {
+	.vidioc_querycap = skeleton_querycap,
+	.vidioc_try_fmt_vid_cap = skeleton_try_fmt_vid_cap,
+	.vidioc_s_fmt_vid_cap = skeleton_s_fmt_vid_cap,
+	.vidioc_g_fmt_vid_cap = skeleton_g_fmt_vid_cap,
+	.vidioc_enum_fmt_vid_cap = skeleton_enum_fmt_vid_cap,
+
+	.vidioc_g_std = skeleton_g_std,
+	.vidioc_s_std = skeleton_s_std,
+	.vidioc_querystd = skeleton_querystd,
+
+	.vidioc_s_dv_timings = skeleton_s_dv_timings,
+	.vidioc_g_dv_timings = skeleton_g_dv_timings,
+	.vidioc_enum_dv_timings = skeleton_enum_dv_timings,
+	.vidioc_query_dv_timings = skeleton_query_dv_timings,
+	.vidioc_dv_timings_cap = skeleton_dv_timings_cap,
+
+	.vidioc_enum_input = skeleton_enum_input,
+	.vidioc_g_input = skeleton_g_input,
+	.vidioc_s_input = skeleton_s_input,
+
+	.vidioc_reqbufs = vb2_ioctl_reqbufs,
+	.vidioc_create_bufs = vb2_ioctl_create_bufs,
+	.vidioc_querybuf = vb2_ioctl_querybuf,
+	.vidioc_qbuf = vb2_ioctl_qbuf,
+	.vidioc_dqbuf = vb2_ioctl_dqbuf,
+	.vidioc_expbuf = vb2_ioctl_expbuf,
+	.vidioc_streamon = vb2_ioctl_streamon,
+	.vidioc_streamoff = vb2_ioctl_streamoff,
+
+	.vidioc_log_status = v4l2_ctrl_log_status,
+	.vidioc_subscribe_event = v4l2_ctrl_subscribe_event,
+	.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
+};
+
+/*
+ * The set of file operations. Note that all these ops are standard core
+ * helper functions.
+ */
+static const struct v4l2_file_operations skel_fops = {
+	.owner = THIS_MODULE,
+	.open = v4l2_fh_open,
+	.release = vb2_fop_release,
+	.unlocked_ioctl = video_ioctl2,
+	.read = vb2_fop_read,
+	.mmap = vb2_fop_mmap,
+	.poll = vb2_fop_poll,
+};
+
+/*
+ * The initial setup of this device instance. Note that the initial state of
+ * the driver should be complete. So the initial format, standard, timings
+ * and video input should all be initialized to some reasonable value.
+ */
+static int skeleton_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
+{
+	/* The initial timings are chosen to be 720p60. */
+	static const struct v4l2_dv_timings timings_def =
+		V4L2_DV_BT_CEA_1280X720P60;
+	struct skeleton *skel;
+	struct video_device *vdev;
+	struct v4l2_ctrl_handler *hdl;
+	struct vb2_queue *q;
+	int ret;
+
+	/* Enable PCI */
+	ret = pci_enable_device(pdev);
+	if (ret)
+		return ret;
+	ret = pci_set_dma_mask(pdev, DMA_BIT_MASK(32));
+	if (ret) {
+		dev_err(&pdev->dev, "no suitable DMA available.\n");
+		goto disable_pci;
+	}
+
+	/* Allocate a new instance */
+	skel = devm_kzalloc(&pdev->dev, sizeof(struct skeleton), GFP_KERNEL);
+	if (!skel)
+		return -ENOMEM;
+
+	/* Allocate the interrupt */
+	ret = devm_request_irq(&pdev->dev, pdev->irq,
+			       skeleton_irq, 0, KBUILD_MODNAME, skel);
+	if (ret) {
+		dev_err(&pdev->dev, "request_irq failed\n");
+		goto disable_pci;
+	}
+	skel->pdev = pdev;
+
+	/* Fill in the initial format-related settings */
+	skel->timings = timings_def;
+	skel->std = V4L2_STD_625_50;
+	skeleton_fill_pix_format(skel, &skel->format);
+
+	/* Initialize the top-level structure */
+	ret = v4l2_device_register(&pdev->dev, &skel->v4l2_dev);
+	if (ret)
+		goto disable_pci;
+
+	mutex_init(&skel->lock);
+
+	/* Add the controls */
+	hdl = &skel->ctrl_handler;
+	v4l2_ctrl_handler_init(hdl, 4);
+	v4l2_ctrl_new_std(hdl, &skel_ctrl_ops,
+			  V4L2_CID_BRIGHTNESS, 0, 255, 1, 127);
+	v4l2_ctrl_new_std(hdl, &skel_ctrl_ops,
+			  V4L2_CID_CONTRAST, 0, 255, 1, 16);
+	v4l2_ctrl_new_std(hdl, &skel_ctrl_ops,
+			  V4L2_CID_SATURATION, 0, 255, 1, 127);
+	v4l2_ctrl_new_std(hdl, &skel_ctrl_ops,
+			  V4L2_CID_HUE, -128, 127, 1, 0);
+	if (hdl->error) {
+		ret = hdl->error;
+		goto free_hdl;
+	}
+	skel->v4l2_dev.ctrl_handler = hdl;
+
+	/* Initialize the vb2 queue */
+	q = &skel->queue;
+	q->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	q->io_modes = VB2_MMAP | VB2_DMABUF | VB2_READ;
+	q->drv_priv = skel;
+	q->buf_struct_size = sizeof(struct skel_buffer);
+	q->ops = &skel_qops;
+	q->mem_ops = &vb2_dma_contig_memops;
+	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
+	/*
+	 * Assume that this DMA engine needs to have at least two buffers
+	 * available before it can be started. The start_streaming() op
+	 * won't be called until at least this many buffers are queued up.
+	 */
+	q->min_buffers_needed = 2;
+	/*
+	 * The serialization lock for the streaming ioctls. This is the same
+	 * as the main serialization lock, but if some of the non-streaming
+	 * ioctls could take a long time to execute, then you might want to
+	 * have a different lock here to prevent VIDIOC_DQBUF from being
+	 * blocked while waiting for another action to finish. This is
+	 * generally not needed for PCI devices, but USB devices usually do
+	 * want a separate lock here.
+	 */
+	q->lock = &skel->lock;
+	/*
+	 * Since this driver can only do 32-bit DMA we must make sure that
+	 * the vb2 core will allocate the buffers in 32-bit DMA memory.
+	 */
+	q->gfp_flags = GFP_DMA32;
+	ret = vb2_queue_init(q);
+	if (ret)
+		goto free_hdl;
+
+	skel->alloc_ctx = vb2_dma_contig_init_ctx(&pdev->dev);
+	if (IS_ERR(skel->alloc_ctx)) {
+		dev_err(&pdev->dev, "Can't allocate buffer context");
+		ret = PTR_ERR(skel->alloc_ctx);
+		goto free_hdl;
+	}
+	INIT_LIST_HEAD(&skel->buf_list);
+	spin_lock_init(&skel->qlock);
+
+	/* Initialize the video_device structure */
+	vdev = &skel->vdev;
+	strlcpy(vdev->name, KBUILD_MODNAME, sizeof(vdev->name));
+	/*
+	 * There is nothing to clean up, so release is set to an empty release
+	 * function. The release callback must be non-NULL.
+	 */
+	vdev->release = video_device_release_empty;
+	vdev->fops = &skel_fops,
+	vdev->ioctl_ops = &skel_ioctl_ops,
+	/*
+	 * The main serialization lock. All ioctls are serialized by this
+	 * lock. Exception: if q->lock is set, then the streaming ioctls
+	 * are serialized by that separate lock.
+	 */
+	vdev->lock = &skel->lock;
+	vdev->queue = q;
+	vdev->v4l2_dev = &skel->v4l2_dev;
+	/* Supported SDTV standards, if any */
+	vdev->tvnorms = SKEL_TVNORMS;
+	/* If this bit is set, then the v4l2 core will provide the support
+	 * for the VIDIOC_G/S_PRIORITY ioctls. This flag will eventually
+	 * go away once all drivers have been converted to use struct v4l2_fh.
+	 */
+	set_bit(V4L2_FL_USE_FH_PRIO, &vdev->flags);
+	video_set_drvdata(vdev, skel);
+
+	ret = video_register_device(vdev, VFL_TYPE_GRABBER, -1);
+	if (ret)
+		goto free_ctx;
+
+	dev_info(&pdev->dev, "V4L2 PCI Skeleton Driver loaded\n");
+	return 0;
+
+free_ctx:
+	vb2_dma_contig_cleanup_ctx(skel->alloc_ctx);
+free_hdl:
+	v4l2_ctrl_handler_free(&skel->ctrl_handler);
+	v4l2_device_unregister(&skel->v4l2_dev);
+disable_pci:
+	pci_disable_device(pdev);
+	return ret;
+}
+
+static void skeleton_remove(struct pci_dev *pdev)
+{
+	struct v4l2_device *v4l2_dev = pci_get_drvdata(pdev);
+	struct skeleton *skel = container_of(v4l2_dev, struct skeleton, v4l2_dev);
+
+	video_unregister_device(&skel->vdev);
+	v4l2_ctrl_handler_free(&skel->ctrl_handler);
+	vb2_dma_contig_cleanup_ctx(skel->alloc_ctx);
+	v4l2_device_unregister(&skel->v4l2_dev);
+	pci_disable_device(skel->pdev);
+}
+
+static struct pci_driver skeleton_driver = {
+	.name = KBUILD_MODNAME,
+	.probe = skeleton_probe,
+	.remove = skeleton_remove,
+	.id_table = skeleton_pci_tbl,
+};
+
+module_pci_driver(skeleton_driver);