On Mon, Feb 05, 2024 at 04:11:43PM +0100, Hans Verkuil wrote:
> On 20/12/2023 11:37, Sakari Ailus wrote:
> > The list of file handles is needed to deliver media events as well as for
> > other purposes in the future.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > ---
> > drivers/media/mc/mc-device.c | 23 ++++++++++++++++++++++-
> > drivers/media/mc/mc-devnode.c | 2 +-
> > include/media/media-devnode.h | 4 +++-
> > 3 files changed, 26 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c
> > index 67a39cb63f89..9cc055deeec9 100644
> > --- a/drivers/media/mc/mc-device.c
> > +++ b/drivers/media/mc/mc-device.c
> > @@ -45,9 +45,11 @@ static inline void __user *media_get_uptr(__u64 arg)
> > return (void __user *)(uintptr_t)arg;
> > }
> >
> > -static int media_device_open(struct file *filp)
> > +static int media_device_open(struct media_devnode *devnode, struct file *filp)
> > {
> > + struct media_device *mdev = to_media_device(devnode);
> > struct media_device_fh *fh;
> > + unsigned long flags;
> >
> > fh = kzalloc(sizeof(*fh), GFP_KERNEL);
> > if (!fh)
> > @@ -55,12 +57,23 @@ static int media_device_open(struct file *filp)
> >
> > filp->private_data = &fh->fh;
> >
> > + spin_lock_irqsave(&mdev->fh_list_lock, flags);
>
> The only reason for using the irqsave variant is because we want
> to support events in the future, and those can be sent in irq context.
Even in that case, would media_device_open() ever be called from
interrupt context ? spin_lock_irqsave() is only needed if you don't know
which context the function can be called from. If we know we'll be
called from interruptible context only, you can use spin_lock_irq()
instead.
> But it is confusing to see this being used here when it is not yet
> needed.
>
> At minimum this should be explained in the commit log.
>
> > + list_add(&fh->mdev_list, &mdev->fh_list);
> > + spin_unlock_irqrestore(&mdev->fh_list_lock, flags);
> > +
> > return 0;
> > }
> >
> > static int media_device_close(struct file *filp)
> > {
> > + struct media_devnode *devnode = media_devnode_data(filp);
> > + struct media_device *mdev = to_media_device(devnode);
> > struct media_device_fh *fh = media_device_fh(filp);
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&mdev->fh_list_lock, flags);
> > + list_del(&fh->mdev_list);
> > + spin_unlock_irqrestore(&mdev->fh_list_lock, flags);
> >
> > kfree(fh);
> >
> > @@ -769,11 +782,13 @@ void media_device_init(struct media_device *mdev)
> > INIT_LIST_HEAD(&mdev->pads);
> > INIT_LIST_HEAD(&mdev->links);
> > INIT_LIST_HEAD(&mdev->entity_notify);
> > + INIT_LIST_HEAD(&mdev->fh_list);
> >
> > mutex_init(&mdev->req_queue_mutex);
> > mutex_init(&mdev->graph_mutex);
> > ida_init(&mdev->entity_internal_idx);
> > atomic_set(&mdev->request_id, 0);
> > + spin_lock_init(&mdev->fh_list_lock);
> >
> > mdev->devnode.release = media_device_release;
> > media_devnode_init(&mdev->devnode);
> > @@ -824,6 +839,8 @@ EXPORT_SYMBOL_GPL(__media_device_register);
> >
> > void media_device_unregister(struct media_device *mdev)
> > {
> > + unsigned long flags;
> > +
> > if (mdev == NULL)
> > return;
> >
> > @@ -834,6 +851,10 @@ void media_device_unregister(struct media_device *mdev)
> > }
> > mutex_unlock(&mdev->graph_mutex);
> >
> > + spin_lock_irqsave(&mdev->fh_list_lock, flags);
> > + list_del_init(&mdev->fh_list);
> > + spin_unlock_irqrestore(&mdev->fh_list_lock, flags);
> > +
> > device_remove_file(&mdev->devnode.dev, &dev_attr_model);
> > dev_dbg(mdev->dev, "Media device unregistering\n");
> > media_devnode_unregister(&mdev->devnode);
> > diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c
> > index 04d376015526..0b5c24828e24 100644
> > --- a/drivers/media/mc/mc-devnode.c
> > +++ b/drivers/media/mc/mc-devnode.c
> > @@ -171,7 +171,7 @@ static int media_open(struct inode *inode, struct file *filp)
> > get_device(&devnode->dev);
> > mutex_unlock(&media_devnode_lock);
> >
> > - ret = devnode->fops->open(filp);
> > + ret = devnode->fops->open(devnode, filp);
> > if (ret) {
> > put_device(&devnode->dev);
> > return ret;
> > diff --git a/include/media/media-devnode.h b/include/media/media-devnode.h
> > index b0efdde4ffd8..840f7ae852d3 100644
> > --- a/include/media/media-devnode.h
> > +++ b/include/media/media-devnode.h
> > @@ -21,6 +21,8 @@
> > #include <linux/device.h>
> > #include <linux/cdev.h>
> >
> > +struct media_devnode;
> > +
> > /*
> > * Flag to mark the media_devnode struct as registered. Drivers must not touch
> > * this flag directly, it will be set and cleared by media_devnode_register and
> > @@ -49,7 +51,7 @@ struct media_file_operations {
> > __poll_t (*poll) (struct file *, struct poll_table_struct *);
> > long (*ioctl) (struct file *, unsigned int, unsigned long);
> > long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
> > - int (*open) (struct file *);
> > + int (*open) (struct media_devnode *, struct file *);
> > int (*release) (struct file *);
> > };
> >
--
Regards,
Laurent Pinchart
