Hi Sakari,
Thank you for the patch.
On Wed, Dec 20, 2023 at 12:36:55PM +0200, Sakari Ailus wrote:
> As registering a device node of an entity belonging to a media device
Did you mean s/As registering/Registering/ ?
> will require a reference to the struct device. Taking that reference is
> only possible once the device has been initialised, which took place only
s/took/takes/
> when it was registered. Split this in two, and initialise the device when
s/was/is/
> the media device is allocated.
>
> Don't distribute the effects of these changes yet. Add media_device_get()
> and media_device_put() first.
Don't propagate the effects of these changes to drivers yet, we want to
expose media_device refcounting with media_device_get() and
media_device_put() functions first.
I'm not sure that's exactly what you meant though.
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Acked-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/mc/mc-device.c | 18 +++++++++++++-----
> drivers/media/mc/mc-devnode.c | 17 ++++++++++-------
> include/media/media-devnode.h | 19 ++++++++++++++-----
> 3 files changed, 37 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c
> index c0ea08a8fc31..ebf037cd5f4a 100644
> --- a/drivers/media/mc/mc-device.c
> +++ b/drivers/media/mc/mc-device.c
> @@ -717,19 +717,26 @@ int __must_check __media_device_register(struct media_device *mdev,
> /* Set version 0 to indicate user-space that the graph is static */
> mdev->topology_version = 0;
>
> + media_devnode_init(&mdev->devnode);
> +
> ret = media_devnode_register(&mdev->devnode, owner);
> if (ret < 0)
> - return ret;
> + goto out_put;
>
> ret = device_create_file(&mdev->devnode.dev, &dev_attr_model);
> - if (ret < 0) {
> - media_devnode_unregister(&mdev->devnode);
> - return ret;
> - }
> + if (ret < 0)
> + goto out_unregister;
>
> dev_dbg(mdev->dev, "Media device registered\n");
>
> return 0;
> +
> +out_unregister:
I would name the labels err_unregister and err_put.
> + media_devnode_unregister(&mdev->devnode);
> +out_put:
> + put_device(&mdev->devnode.dev);
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(__media_device_register);
>
> @@ -803,6 +810,7 @@ void media_device_unregister(struct media_device *mdev)
> device_remove_file(&mdev->devnode.dev, &dev_attr_model);
> dev_dbg(mdev->dev, "Media device unregistering\n");
> media_devnode_unregister(&mdev->devnode);
> + put_device(&mdev->devnode.dev);
> }
> EXPORT_SYMBOL_GPL(media_device_unregister);
>
> diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c
> index 8bc7450ac144..7b17419050fb 100644
> --- a/drivers/media/mc/mc-devnode.c
> +++ b/drivers/media/mc/mc-devnode.c
> @@ -204,6 +204,11 @@ static const struct file_operations media_devnode_fops = {
> .llseek = no_llseek,
> };
>
> +void media_devnode_init(struct media_devnode *devnode)
> +{
> + device_initialize(&devnode->dev);
> +}
> +
> int __must_check media_devnode_register(struct media_devnode *devnode,
> struct module *owner)
> {
> @@ -235,7 +240,6 @@ int __must_check media_devnode_register(struct media_devnode *devnode,
> if (devnode->parent)
> devnode->dev.parent = devnode->parent;
> dev_set_name(&devnode->dev, "media%d", devnode->minor);
> - device_initialize(&devnode->dev);
>
> /* Part 3: Add the media and character devices */
> ret = cdev_device_add(&devnode->cdev, &devnode->dev);
> @@ -267,14 +271,13 @@ void media_devnode_unregister(struct media_devnode *devnode)
> clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
> mutex_unlock(&media_devnode_lock);
>
> - cdev_del(&devnode->cdev);
> - device_unregister(&devnode->dev);
> + cdev_device_del(&devnode->cdev, &devnode->dev);
> }
>
> /*
> * Initialise media for linux
> */
> -static int __init media_devnode_init(void)
> +static int __init media_devnode_module_init(void)
> {
> int ret;
>
> @@ -296,14 +299,14 @@ static int __init media_devnode_init(void)
> return 0;
> }
>
> -static void __exit media_devnode_exit(void)
> +static void __exit media_devnode_module_exit(void)
> {
> bus_unregister(&media_bus_type);
> unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
> }
>
> -subsys_initcall(media_devnode_init);
> -module_exit(media_devnode_exit)
> +subsys_initcall(media_devnode_module_init);
> +module_exit(media_devnode_module_exit)
>
> MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>");
> MODULE_DESCRIPTION("Device node registration for media drivers");
> diff --git a/include/media/media-devnode.h b/include/media/media-devnode.h
> index 1117d1dfd6bf..6d46c658be21 100644
> --- a/include/media/media-devnode.h
> +++ b/include/media/media-devnode.h
> @@ -90,6 +90,17 @@ struct media_devnode {
> /* dev to media_devnode */
> #define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
>
> +/**
> + * media_devnode_init - initialise a media devnode
> + *
> + * @devnode: struct media_devnode we want to initialise
> + *
> + * Initialise a media devnode. Note that after initialising the media
> + * devnode is refcounted. Releasing references to it may be done using
> + * put_device().
> + */
> +void media_devnode_init(struct media_devnode *devnode);
> +
> /**
> * media_devnode_register - register a media device node
> *
> @@ -100,11 +111,9 @@ struct media_devnode {
> * with the kernel. An error is returned if no free minor number can be found,
> * or if the registration of the device node fails.
> *
> - * Zero is returned on success.
> - *
> - * Note that if the media_devnode_register call fails, the release() callback of
> - * the media_devnode structure is *not* called, so the caller is responsible for
> - * freeing any data.
> + * Zero is returned on success. Note that in case
> + * media_devnode_register() fails, the caller is responsible for
> + * releasing the reference to the device using put_device().
> */
> int __must_check media_devnode_register(struct media_devnode *devnode,
> struct module *owner);
--
Regards,
Laurent Pinchart
