On 05/23/2016 05:39 AM, Hans Verkuil wrote:
> On 05/13/2016 07:09 PM, Shuah Khan wrote:
>> Add media_device_unregister_put() interface to release reference to a media
>> device allocated using the Media Device Allocator API. The media device is
>> unregistered and freed when the last driver that holds the reference to the
>> media device releases the reference. The media device is unregistered and
>> freed in the kref put handler.
>>
>> Signed-off-by: Shuah Khan <shua...@osg.samsung.com>
>> ---
>> drivers/media/media-device.c | 11 +++++++++++
>> include/media/media-device.h | 15 +++++++++++++++
>> 2 files changed, 26 insertions(+)
>>
>> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
>> index 33a9952..b5c279a 100644
>> --- a/drivers/media/media-device.c
>> +++ b/drivers/media/media-device.c
>> @@ -36,6 +36,7 @@
>> #include <media/media-device.h>
>> #include <media/media-devnode.h>
>> #include <media/media-entity.h>
>> +#include <media/media-dev-allocator.h>
>>
>> #ifdef CONFIG_MEDIA_CONTROLLER
>>
>> @@ -818,6 +819,16 @@ void media_device_unregister(struct media_device *mdev)
>> }
>> EXPORT_SYMBOL_GPL(media_device_unregister);
>>
>> +void media_device_unregister_put(struct media_device *mdev)
>> +{
>> + if (mdev == NULL)
>> + return;
>> +
>> + dev_dbg(mdev->dev, "%s: mdev %p\n", __func__, mdev);
>> + media_device_put(mdev);
>> +}
>> +EXPORT_SYMBOL_GPL(media_device_unregister_put);
>> +
>
> I don't really see the need for a new unregister_put function. The only thing
> it adds compared to media_device_put is the 'if (mdev == NULL)' check.
>
> Is that check needed at all?
Yeah. My reasoning for keeping this for symmetry in drivers
with _register() and _unregister(). However, drivers already
required to call media_device_put() in _register error legs.
>
> I would probably go for an API like this:
>
> <brainstorm mode on>
>
> /* Not sure if there should be a void *priv as the last argument */
> int (*mdev_init_fnc)(struct media_device *mdev, struct device *dev);
>
> /* Perhaps a void *priv is needed to pass to mdev_init_fnc?
> The callback is there to initialize the media_device and it's called
> with the lock held.
> */
> struct media_device *media_device_allocate(struct device *dev, mdev_init_fnc
> fnc);
>
> /* Helper function for usb devices */
> struct media_device *media_device_usb_allocate(struct usb_device *udev,
> char *driver_name);
>
> /* counterpart of media_device_allocate, that makes more sense than
> allocate/put IMHO */
> void media_device_release(struct media_device *mdev);
We already have a media_device_release() that gets used as devnode->release
back. I will use a different name, media_device_usb_free() or something
similar.
>
> <brainstorm mode off>
>
> Regards,
>
> Hans
>
>> static void media_device_release_devres(struct device *dev, void *res)
>> {
>> }
>> diff --git a/include/media/media-device.h b/include/media/media-device.h
>> index f743ae2..8bd836e 100644
>> --- a/include/media/media-device.h
>> +++ b/include/media/media-device.h
>> @@ -499,6 +499,18 @@ int __must_check __media_device_register(struct
>> media_device *mdev,
>> void media_device_unregister(struct media_device *mdev);
>>
>> /**
>> + * media_device_unregister_put() - Unregisters a media device element
>> + *
>> + * @mdev: pointer to struct &media_device
>> + *
>> + * Should be called to unregister media device allocated with Media Device
>> + * Allocator API media_device_get() interface.
>> + * It is safe to call this function on an unregistered (but initialised)
>> + * media device.
>> + */
>> +void media_device_unregister_put(struct media_device *mdev);
>> +
>> +/**
>> * media_device_register_entity() - registers a media entity inside a
>> * previously registered media device.
>> *
>> @@ -658,6 +670,9 @@ static inline int media_device_register(struct
>> media_device *mdev)
>> static inline void media_device_unregister(struct media_device *mdev)
>> {
>> }
>> +static inline void media_device_unregister_put(struct media_device *mdev)
>> +{
>> +}
>> static inline int media_device_register_entity(struct media_device *mdev,
>> struct media_entity *entity)
>> {
>>
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