Re: [PATCH v2 1/2] media: new media controller API for device resource support

[Mauro Carvalho Chehab <mchehab@osg.samsung.com>]

Em Wed, 03 Jun 2015 09:12:53 -0600
Shuah Khan <shuahkh@osg.samsung.com> escreveu:

> Add new media controller API to allocate media device as a
> device resource. When a media device is created on the main
> struct device which is the parent device for the interface
> device, it will be available to all drivers associated with
> that interface. For example, if a usb media device driver
> creates the media device on the main struct device which is
> common for all the drivers that control the media device,
> including the non-media ALSA driver, media controller API
> can be used to share access to the resources on the media
> device. This new interface provides the above described
> feature. A second interface that finds and returns the media
> device is added to allow drivers to find the media device
> created by any of the drivers associated with the device.
> 
> Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
> ---
>  drivers/media/media-device.c | 33 +++++++++++++++++++++++++++++++++
>  include/media/media-device.h |  2 ++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index 7b39440..a4d5b24 100644
> --- a/drivers/media/media-device.c
> +++ b/drivers/media/media-device.c
> @@ -462,3 +462,36 @@ void media_device_unregister_entity(struct media_entity *entity)
>  	entity->parent = NULL;
>  }
>  EXPORT_SYMBOL_GPL(media_device_unregister_entity);
> +
> +static void media_device_release_devres(struct device *dev, void *res)
> +{
> +}
> +
> +/*
> + * media_device_get_devres() -	get media device as device resource
> + *				creates if one doesn't exist
> +*/
> +struct media_device *media_device_get_devres(struct device *dev)
> +{
> +	struct media_device *mdev;
> +
> +	mdev = devres_find(dev, media_device_release_devres, NULL, NULL);
> +	if (mdev)
> +		return mdev;
> +
> +	mdev = devres_alloc(media_device_release_devres,
> +				sizeof(struct media_device), GFP_KERNEL);
> +	if (!mdev)
> +		return NULL;
> +	return devres_get(dev, mdev, NULL, NULL);
> +}
> +EXPORT_SYMBOL_GPL(media_device_get_devres);
> +
> +/*
> + * media_device_find_devres() - find media device as device resource
> +*/
> +struct media_device *media_device_find_devres(struct device *dev)
> +{
> +	return devres_find(dev, media_device_release_devres, NULL, NULL);
> +}
> +EXPORT_SYMBOL_GPL(media_device_find_devres);
> diff --git a/include/media/media-device.h b/include/media/media-device.h
> index 6e6db78..22792cd 100644
> --- a/include/media/media-device.h
> +++ b/include/media/media-device.h
> @@ -95,6 +95,8 @@ void media_device_unregister(struct media_device *mdev);
>  int __must_check media_device_register_entity(struct media_device *mdev,
>  					      struct media_entity *entity);
>  void media_device_unregister_entity(struct media_entity *entity);
> +struct media_device *media_device_get_devres(struct device *dev);
> +struct media_device *media_device_find_devres(struct device *dev);

Hmm... what happens if the Kernel is compiled without MC controller
support?

I think that the best would be to add a #ifdef at the header file and
provide an alternate dummy method to avoid the need of testing for it
everywhere.

>  
>  /* Iterate over all entities. */
>  #define media_device_for_each_entity(entity, mdev)			\