Hi Andrey,
Here is a quick review of this staging V4L2 driver, and some additional notes
for testing at the end:
> // SPDX-License-Identifier: GPL-2.0
> /*
> * video.c - V4L2 component for Mostcore
> *
> * Copyright (C) 2015, Microchip Technology Germany II GmbH & Co. KG
> */
>
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> #include <linux/module.h>
> #include <linux/slab.h>
> #include <linux/init.h>
> #include <linux/device.h>
> #include <linux/suspend.h>
> #include <linux/videodev2.h>
> #include <linux/mutex.h>
> #include <media/v4l2-common.h>
> #include <media/v4l2-ioctl.h>
> #include <media/v4l2-event.h>
> #include <media/v4l2-device.h>
> #include <media/v4l2-ctrls.h>
> #include <media/v4l2-fh.h>
>
> #include "most/core.h"
>
> #define V4L2_CMP_MAX_INPUT 1
>
> static struct core_component comp;
>
> struct most_video_dev {
> struct most_interface *iface;
> int ch_idx;
> struct list_head list;
> bool mute;
>
> struct list_head pending_mbos;
> spinlock_t list_lock;
>
> struct v4l2_device v4l2_dev;
> atomic_t access_ref;
> struct video_device *vdev;
> unsigned int ctrl_input;
>
> struct mutex lock;
>
> wait_queue_head_t wait_data;
> };
>
> struct comp_fh {
> /* must be the first field of this struct! */
> struct v4l2_fh fh;
> struct most_video_dev *mdev;
> u32 offs;
> };
>
> static struct list_head video_devices = LIST_HEAD_INIT(video_devices);
> static struct spinlock list_lock;
>
> static inline bool data_ready(struct most_video_dev *mdev)
> {
> return !list_empty(&mdev->pending_mbos);
> }
>
> static inline struct mbo *get_top_mbo(struct most_video_dev *mdev)
> {
> return list_first_entry(&mdev->pending_mbos, struct mbo, list);
> }
>
> static int comp_vdev_open(struct file *filp)
> {
> int ret;
> struct video_device *vdev = video_devdata(filp);
> struct most_video_dev *mdev = video_drvdata(filp);
> struct comp_fh *fh;
>
> switch (vdev->vfl_type) {
> case VFL_TYPE_GRABBER:
> break;
> default:
> return -EINVAL;
> }
No need for this check, it can't be anything else.
>
> fh = kzalloc(sizeof(*fh), GFP_KERNEL);
> if (!fh)
> return -ENOMEM;
>
> if (!atomic_inc_and_test(&mdev->access_ref)) {
> v4l2_err(&mdev->v4l2_dev, "too many clients\n");
> ret = -EBUSY;
> goto err_dec;
> }
NACK: it is not allowed to limit the number of clients, anyone should
be able to e.g. query the capabilities. There can however be only one
client that is streaming video at a time.
>
> fh->mdev = mdev;
> v4l2_fh_init(&fh->fh, vdev);
> filp->private_data = fh;
>
> v4l2_fh_add(&fh->fh);
>
> ret = most_start_channel(mdev->iface, mdev->ch_idx, &comp);
This is the wrong place. This should be done on the first read() and
if you poll() for data and the channel isn't started yet. Not during open().
Otherwise a simple VIDIOC_QUERYCAP would cause a channel to be started,
that's not what you want.
I would also strongly suggest that you use the vb2 framework: that way
you get streaming I/O capabilities for free.
> if (ret) {
> v4l2_err(&mdev->v4l2_dev, "most_start_channel() failed\n");
> goto err_rm;
> }
>
> return 0;
>
> err_rm:
> v4l2_fh_del(&fh->fh);
> v4l2_fh_exit(&fh->fh);
>
> err_dec:
> atomic_dec(&mdev->access_ref);
> kfree(fh);
> return ret;
> }
>
> static int comp_vdev_close(struct file *filp)
> {
> struct comp_fh *fh = filp->private_data;
> struct most_video_dev *mdev = fh->mdev;
> struct mbo *mbo, *tmp;
>
> /*
> * We need to put MBOs back before we call most_stop_channel()
> * to deallocate MBOs.
> * From the other hand mostcore still calling rx_completion()
> * to deliver MBOs until most_stop_channel() is called.
> * Use mute to work around this issue.
> * This must be implemented in core.
> */
>
> spin_lock_irq(&mdev->list_lock);
> mdev->mute = true;
> list_for_each_entry_safe(mbo, tmp, &mdev->pending_mbos, list) {
> list_del(&mbo->list);
> spin_unlock_irq(&mdev->list_lock);
> most_put_mbo(mbo);
> spin_lock_irq(&mdev->list_lock);
> }
> spin_unlock_irq(&mdev->list_lock);
> most_stop_channel(mdev->iface, mdev->ch_idx, &comp);
> mdev->mute = false;
>
> v4l2_fh_del(&fh->fh);
> v4l2_fh_exit(&fh->fh);
>
> atomic_dec(&mdev->access_ref);
> kfree(fh);
> return 0;
> }
>
> static ssize_t comp_vdev_read(struct file *filp, char __user *buf,
> size_t count, loff_t *pos)
> {
> struct comp_fh *fh = filp->private_data;
> struct most_video_dev *mdev = fh->mdev;
> int ret = 0;
>
> if (*pos)
> return -ESPIPE;
>
> if (!mdev)
> return -ENODEV;
>
> /* wait for the first buffer */
> if (!(filp->f_flags & O_NONBLOCK)) {
> if (wait_event_interruptible(mdev->wait_data, data_ready(mdev)))
> return -ERESTARTSYS;
> }
>
> if (!data_ready(mdev))
> return -EAGAIN;
>
> while (count > 0 && data_ready(mdev)) {
> struct mbo *const mbo = get_top_mbo(mdev);
> int const rem = mbo->processed_length - fh->offs;
> int const cnt = rem < count ? rem : count;
>
> if (copy_to_user(buf, mbo->virt_address + fh->offs, cnt)) {
> v4l2_err(&mdev->v4l2_dev, "read: copy_to_user
> failed\n");
> if (!ret)
> ret = -EFAULT;
> return ret;
> }
>
> fh->offs += cnt;
> count -= cnt;
> buf += cnt;
> ret += cnt;
>
> if (cnt >= rem) {
> fh->offs = 0;
> spin_lock_irq(&mdev->list_lock);
> list_del(&mbo->list);
> spin_unlock_irq(&mdev->list_lock);
> most_put_mbo(mbo);
> }
> }
> return ret;
> }
>
> static __poll_t comp_vdev_poll(struct file *filp, poll_table *wait)
> {
> struct comp_fh *fh = filp->private_data;
> struct most_video_dev *mdev = fh->mdev;
> __poll_t mask = 0;
>
> /* only wait if no data is available */
> if (!data_ready(mdev))
> poll_wait(filp, &mdev->wait_data, wait);
poll_wait should always be done, also when there is data available.
Otherwise epoll() can fail.
> if (data_ready(mdev))
> mask |= EPOLLIN | EPOLLRDNORM;
>
> return mask;
> }
>
> static void comp_set_format_struct(struct v4l2_format *f)
> {
> f->fmt.pix.width = 8;
> f->fmt.pix.height = 8;
I guess you have no metadata available about the video resolution?
> f->fmt.pix.pixelformat = V4L2_PIX_FMT_MPEG;
> f->fmt.pix.bytesperline = 0;
> f->fmt.pix.sizeimage = 188 * 2;
> f->fmt.pix.colorspace = V4L2_COLORSPACE_REC709;
> f->fmt.pix.field = V4L2_FIELD_NONE;
> f->fmt.pix.priv = 0;
No need to set priv, just drop this line.
> }
>
> static int comp_set_format(struct most_video_dev *mdev, unsigned int cmd,
> struct v4l2_format *format)
> {
> if (format->fmt.pix.pixelformat != V4L2_PIX_FMT_MPEG)
> return -EINVAL;
>
> if (cmd == VIDIOC_TRY_FMT)
> return 0;
>
> comp_set_format_struct(format);
>
> return 0;
> }
I'd drop this. Instead just route .vidioc_g/s/try_fmt_vid_cap to the
same function. There is only one hardcoded format, so no need to
differentiate between the three ops.
>
> static int vidioc_querycap(struct file *file, void *priv,
> struct v4l2_capability *cap)
> {
> struct comp_fh *fh = priv;
> struct most_video_dev *mdev = fh->mdev;
>
> strlcpy(cap->driver, "v4l2_component", sizeof(cap->driver));
That's a bad name. "most-video" or something is much more specific.
> strlcpy(cap->card, "MOST", sizeof(cap->card));
strlcpy -> strscpy
The media subsystem standardized on strscpy.
> snprintf(cap->bus_info, sizeof(cap->bus_info),
> "%s", mdev->iface->description);
What does the bus_info look like? The convention is that it should
be 1) unique and 2) start with a prefix describing the bus. In this
case that is probably 'most:'.
>
> cap->capabilities =
> V4L2_CAP_READWRITE |
> V4L2_CAP_TUNER |
> V4L2_CAP_VIDEO_CAPTURE;
I already posted a patch correcting this.
> return 0;
> }
>
> static int vidioc_enum_fmt_vid_cap(struct file *file, void *priv,
> struct v4l2_fmtdesc *f)
> {
> if (f->index)
> return -EINVAL;
>
> strcpy(f->description, "MPEG");
> f->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> f->flags = V4L2_FMT_FLAG_COMPRESSED;
Drop these three lines: the V4L2 core will fill this in for you.
> f->pixelformat = V4L2_PIX_FMT_MPEG;
>
> return 0;
> }
>
> static int vidioc_g_fmt_vid_cap(struct file *file, void *priv,
> struct v4l2_format *f)
> {
> comp_set_format_struct(f);
> return 0;
> }
>
> static int vidioc_try_fmt_vid_cap(struct file *file, void *priv,
> struct v4l2_format *f)
> {
> struct comp_fh *fh = priv;
> struct most_video_dev *mdev = fh->mdev;
>
> return comp_set_format(mdev, VIDIOC_TRY_FMT, f);
> }
>
> static int vidioc_s_fmt_vid_cap(struct file *file, void *priv,
> struct v4l2_format *f)
> {
> struct comp_fh *fh = priv;
> struct most_video_dev *mdev = fh->mdev;
>
> return comp_set_format(mdev, VIDIOC_S_FMT, f);
> }
>
> static int vidioc_g_std(struct file *file, void *priv, v4l2_std_id *norm)
> {
> *norm = V4L2_STD_UNKNOWN;
> return 0;
> }
Why is this needed? This op can be dropped.
>
> static int vidioc_enum_input(struct file *file, void *priv,
> struct v4l2_input *input)
> {
> struct comp_fh *fh = priv;
> struct most_video_dev *mdev = fh->mdev;
>
> if (input->index >= V4L2_CMP_MAX_INPUT)
> return -EINVAL;
>
> strcpy(input->name, "MOST Video");
Use strscpy.
> input->type |= V4L2_INPUT_TYPE_CAMERA;
Use = instead of |=
> input->audioset = 0;
>
> input->std = mdev->vdev->tvnorms;
Drop these two lines, the V4L2 core zeroed these fields for you.
>
> return 0;
> }
>
> static int vidioc_g_input(struct file *file, void *priv, unsigned int *i)
> {
> struct comp_fh *fh = priv;
> struct most_video_dev *mdev = fh->mdev;
> *i = mdev->ctrl_input;
> return 0;
> }
>
> static int vidioc_s_input(struct file *file, void *priv, unsigned int index)
> {
> struct comp_fh *fh = priv;
> struct most_video_dev *mdev = fh->mdev;
>
> if (index >= V4L2_CMP_MAX_INPUT)
> return -EINVAL;
> mdev->ctrl_input = index;
> return 0;
> }
>
> static const struct v4l2_file_operations comp_fops = {
> .owner = THIS_MODULE,
> .open = comp_vdev_open,
> .release = comp_vdev_close,
> .read = comp_vdev_read,
> .poll = comp_vdev_poll,
> .unlocked_ioctl = video_ioctl2,
> };
>
> static const struct v4l2_ioctl_ops video_ioctl_ops = {
> .vidioc_querycap = vidioc_querycap,
> .vidioc_enum_fmt_vid_cap = vidioc_enum_fmt_vid_cap,
> .vidioc_g_fmt_vid_cap = vidioc_g_fmt_vid_cap,
> .vidioc_try_fmt_vid_cap = vidioc_try_fmt_vid_cap,
> .vidioc_s_fmt_vid_cap = vidioc_s_fmt_vid_cap,
> .vidioc_g_std = vidioc_g_std,
> .vidioc_enum_input = vidioc_enum_input,
> .vidioc_g_input = vidioc_g_input,
> .vidioc_s_input = vidioc_s_input,
> };
>
> static const struct video_device comp_videodev_template = {
> .fops = &comp_fops,
> .release = video_device_release,
> .ioctl_ops = &video_ioctl_ops,
> .tvnorms = V4L2_STD_UNKNOWN,
Drop this line. No need to zero tvnorms.
> };
>
> /**************************************************************************/
>
> static struct most_video_dev *get_comp_dev(
> struct most_interface *iface, int channel_idx)
> {
> struct most_video_dev *mdev;
> unsigned long flags;
>
> spin_lock_irqsave(&list_lock, flags);
> list_for_each_entry(mdev, &video_devices, list) {
> if (mdev->iface == iface && mdev->ch_idx == channel_idx) {
> spin_unlock_irqrestore(&list_lock, flags);
> return mdev;
> }
> }
> spin_unlock_irqrestore(&list_lock, flags);
> return NULL;
> }
>
> static int comp_rx_data(struct mbo *mbo)
> {
> unsigned long flags;
> struct most_video_dev *mdev =
> get_comp_dev(mbo->ifp, mbo->hdm_channel_id);
>
> if (!mdev)
> return -EIO;
>
> spin_lock_irqsave(&mdev->list_lock, flags);
> if (unlikely(mdev->mute)) {
> spin_unlock_irqrestore(&mdev->list_lock, flags);
> return -EIO;
> }
>
> list_add_tail(&mbo->list, &mdev->pending_mbos);
> spin_unlock_irqrestore(&mdev->list_lock, flags);
> wake_up_interruptible(&mdev->wait_data);
> return 0;
> }
>
> static int comp_register_videodev(struct most_video_dev *mdev)
> {
> int ret;
>
> init_waitqueue_head(&mdev->wait_data);
>
> /* allocate and fill v4l2 video struct */
> mdev->vdev = video_device_alloc();
> if (!mdev->vdev)
> return -ENOMEM;
>
> /* Fill the video capture device struct */
> *mdev->vdev = comp_videodev_template;
> mdev->vdev->v4l2_dev = &mdev->v4l2_dev;
> mdev->vdev->lock = &mdev->lock;
> snprintf(mdev->vdev->name, sizeof(mdev->vdev->name), "MOST: %s",
> mdev->v4l2_dev.name);
>
> /* Register the v4l2 device */
> video_set_drvdata(mdev->vdev, mdev);
> ret = video_register_device(mdev->vdev, VFL_TYPE_GRABBER, -1);
> if (ret) {
> v4l2_err(&mdev->v4l2_dev, "video_register_device failed (%d)\n",
> ret);
> video_device_release(mdev->vdev);
> }
>
> return ret;
> }
>
> static void comp_unregister_videodev(struct most_video_dev *mdev)
> {
> video_unregister_device(mdev->vdev);
> }
>
> static void comp_v4l2_dev_release(struct v4l2_device *v4l2_dev)
> {
> struct most_video_dev *mdev =
> container_of(v4l2_dev, struct most_video_dev, v4l2_dev);
>
> v4l2_device_unregister(v4l2_dev);
> kfree(mdev);
> }
>
> static int comp_probe_channel(struct most_interface *iface, int channel_idx,
> struct most_channel_config *ccfg, char *name,
> char *args)
> {
> int ret;
> struct most_video_dev *mdev = get_comp_dev(iface, channel_idx);
>
> if (mdev) {
> pr_err("channel already linked\n");
> return -EEXIST;
> }
>
> if (ccfg->direction != MOST_CH_RX) {
> pr_err("wrong direction, expect rx\n");
> return -EINVAL;
> }
>
> if (ccfg->data_type != MOST_CH_SYNC &&
> ccfg->data_type != MOST_CH_ISOC) {
> pr_err("wrong channel type, expect sync or isoc\n");
> return -EINVAL;
> }
>
> mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
> if (!mdev)
> return -ENOMEM;
>
> mutex_init(&mdev->lock);
> atomic_set(&mdev->access_ref, -1);
> spin_lock_init(&mdev->list_lock);
> INIT_LIST_HEAD(&mdev->pending_mbos);
> mdev->iface = iface;
> mdev->ch_idx = channel_idx;
> mdev->v4l2_dev.release = comp_v4l2_dev_release;
>
> /* Create the v4l2_device */
> strlcpy(mdev->v4l2_dev.name, name, sizeof(mdev->v4l2_dev.name));
strscpy
> ret = v4l2_device_register(NULL, &mdev->v4l2_dev);
You don't have a suitable parent device here?
> if (ret) {
> pr_err("v4l2_device_register() failed\n");
> kfree(mdev);
> return ret;
> }
>
> ret = comp_register_videodev(mdev);
> if (ret)
> goto err_unreg;
>
> spin_lock_irq(&list_lock);
> list_add(&mdev->list, &video_devices);
> spin_unlock_irq(&list_lock);
> return 0;
>
> err_unreg:
> v4l2_device_disconnect(&mdev->v4l2_dev);
> v4l2_device_put(&mdev->v4l2_dev);
> return ret;
> }
>
> static int comp_disconnect_channel(struct most_interface *iface,
> int channel_idx)
> {
> struct most_video_dev *mdev = get_comp_dev(iface, channel_idx);
>
> if (!mdev) {
> pr_err("no such channel is linked\n");
> return -ENOENT;
> }
>
> spin_lock_irq(&list_lock);
> list_del(&mdev->list);
> spin_unlock_irq(&list_lock);
>
> comp_unregister_videodev(mdev);
> v4l2_device_disconnect(&mdev->v4l2_dev);
> v4l2_device_put(&mdev->v4l2_dev);
> return 0;
> }
>
> static struct core_component comp = {
> .name = "video",
> .probe_channel = comp_probe_channel,
> .disconnect_channel = comp_disconnect_channel,
> .rx_completion = comp_rx_data,
> };
>
> static int __init comp_init(void)
> {
> spin_lock_init(&list_lock);
> return most_register_component(&comp);
> }
>
> static void __exit comp_exit(void)
> {
> struct most_video_dev *mdev, *tmp;
>
> /*
> * As the mostcore currently doesn't call disconnect_channel()
> * for linked channels while we call most_deregister_component()
> * we simulate this call here.
> * This must be fixed in core.
> */
> spin_lock_irq(&list_lock);
> list_for_each_entry_safe(mdev, tmp, &video_devices, list) {
> list_del(&mdev->list);
> spin_unlock_irq(&list_lock);
>
> comp_unregister_videodev(mdev);
> v4l2_device_disconnect(&mdev->v4l2_dev);
> v4l2_device_put(&mdev->v4l2_dev);
> spin_lock_irq(&list_lock);
> }
> spin_unlock_irq(&list_lock);
>
> most_deregister_component(&comp);
> BUG_ON(!list_empty(&video_devices));
> }
>
> module_init(comp_init);
> module_exit(comp_exit);
>
> MODULE_DESCRIPTION("V4L2 Component Module for Mostcore");
> MODULE_AUTHOR("Andrey Shvetsov <andrey.shvet...@k2l.de>");
> MODULE_LICENSE("GPL");
Finally some test notes: please use the v4l2-compliance utility to test the
driver. It's available as part of our v4l-utils repository:
https://git.linuxtv.org//v4l-utils.git
First just run it as 'v4l2-compliance -d /dev/videoX' and fix any issues
(ask me if you have questions).
Next add the '-s' option to also test read() support.
As mentioned, I think you should try and switch to the vb2 framework
since you'll get a lot of functionality almost for free, and most applications
assume that the streaming I/O ioctls are available.
Regards,
Hans
