btrfs: fix locking when we put back a delayed ref that's too new

[linux/fpc-iii.git] / samples / v4l / 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-v4l2.h>
#include <media/videobuf2-dma-contig.h>

MODULE_DESCRIPTION("V4L2 PCI Skeleton Driver");
MODULE_AUTHOR("Hans Verkuil");
MODULE_LICENSE("GPL v2");

/**
 * 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
 * @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;

        spinlock_t qlock;
        struct list_head buf_list;
        unsigned field;
        unsigned 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, }
};
MODULE_DEVICE_TABLE(pci, skeleton_pci_tbl);

/*
 * 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, field 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);
                v4l2_get_timestamp(&new_buf->vb.v4l2_buf.timestamp);
                new_buf->vb.v4l2_buf.sequence = skel->sequence++;
                new_buf->vb.v4l2_buf.field = skel->field;
                if (skel->format.field == V4L2_FIELD_ALTERNATE) {
                        if (skel->field == V4L2_FIELD_BOTTOM)
                                skel->field = V4L2_FIELD_TOP;
                        else if (skel->field == V4L2_FIELD_TOP)
                                skel->field = V4L2_FIELD_BOTTOM;
                }
                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,
                       unsigned int *nbuffers, unsigned int *nplanes,
                       unsigned int sizes[], struct device *alloc_devs[])
{
        struct skeleton *skel = vb2_get_drv_priv(vq);

        skel->field = skel->format.field;
        if (skel->field == V4L2_FIELD_ALTERNATE) {
                /*
                 * You cannot use read() with FIELD_ALTERNATE since the field
                 * information (TOP/BOTTOM) cannot be passed back to the user.
                 */
                if (vb2_fileio_is_active(vq))
                        return -EINVAL;
                skel->field = V4L2_FIELD_TOP;
        }

        if (vq->num_buffers + *nbuffers < 3)
                *nbuffers = 3 - vq->num_buffers;

        if (*nplanes)
                return sizes[0] < skel->format.sizeimage ? -EINVAL : 0;
        *nplanes = 1;
        sizes[0] = skel->format.sizeimage;
        return 0;
}

/*
 * Prepare the buffer for queueing to the DMA engine: check and set the
 * payload size.
 */
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);
        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 void 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);
}

/*
 * 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));
        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_ALTERNATE;
                        pix->height /= 2;
                } 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;

        f->pixelformat = V4L2_PIX_FMT_YUYV;
        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, false))
                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->dev = &pdev->dev;
        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;

        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,
        vdev->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_READWRITE |
                            V4L2_CAP_STREAMING;
        /*
         * 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;
        video_set_drvdata(vdev, skel);

        ret = video_register_device(vdev, VFL_TYPE_GRABBER, -1);
        if (ret)
                goto free_hdl;

        dev_info(&pdev->dev, "V4L2 PCI Skeleton Driver loaded\n");
        return 0;

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);
        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);