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 12:14:09 -0600
Shuah Khan <shuahkh@osg.samsung.com> escreveu:

> On 06/03/2015 11:42 AM, Mauro Carvalho Chehab wrote:
> > 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?
> 
> Yeah. I noticed media controller api users have the code in ifdef
> CONFIG_MEDIA_CONTROLLER.
> 
> > 
> > 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.
> > 
> 
> I agree with you that a better way to do it would be defining media
> controller api in ifdef CONFIG_MEDIA_CONTROLLER and provide stubs for
> else case, similar to what I did in sound/usb/media.c
> 
> I followed the existing code to add new interfaces. Do you want to see
> all media controller interfaces in ifdef clause with stubs or just the
> two new interfaces I added? Or is this something that should be done as
> a separate change to catch all media controller interfaces?

It could be on a separate patch. IMHO, the best is to put all defines
on stubs.

> 
> thanks,
> -- Shuah
>