[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 <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

1 files changed, 913 insertions, 0 deletions

diff --git a/Documentation/video4linux/v4l2-pci-skeleton.c b/Documentation/video4linux/v4l2-pci-skeleton.c
new file mode 100644
index 000000000000..3a1c0d2dafce
--- /dev/null
+++ b/Documentation/video4linux/v4l2-pci-skeleton.c
@@ -0,0 +1,913 @@
+/*
+ * 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);