1.18. V4L2 Media Controller functions and data structures

enum tuner_pad_index

tuner pad index for MEDIA_ENT_F_TUNER

Constants

TUNER_PAD_RF_INPUT

Radiofrequency (RF) sink pad, usually linked to a RF connector entity.

TUNER_PAD_OUTPUT

Tuner video output source pad. Contains the video chrominance and luminance or the hole bandwidth of the signal converted to an Intermediate Frequency (IF) or to baseband (on zero-IF tuners).

TUNER_PAD_AUD_OUT

Tuner audio output source pad. Tuners used to decode analog TV signals have an extra pad for audio output. Old tuners use an analog stage with a saw filter for the audio IF frequency. The output of the pad is, in this case, the audio IF, with should be decoded either by the bridge chipset (that’s the case of cx2388x chipsets) or may require an external IF sound processor, like msp34xx. On modern silicon tuners, the audio IF decoder is usually incorporated at the tuner. On such case, the output of this pad is an audio sampled data.

TUNER_NUM_PADS

Number of pads of the tuner.

enum if_vid_dec_pad_index

video IF-PLL pad index for MEDIA_ENT_F_IF_VID_DECODER

Constants

IF_VID_DEC_PAD_IF_INPUT

video Intermediate Frequency (IF) sink pad

IF_VID_DEC_PAD_OUT

IF-PLL video output source pad. Contains the video chrominance and luminance IF signals.

IF_VID_DEC_PAD_NUM_PADS

Number of pads of the video IF-PLL.

enum if_aud_dec_pad_index

audio/sound IF-PLL pad index for MEDIA_ENT_F_IF_AUD_DECODER

Constants

IF_AUD_DEC_PAD_IF_INPUT

audio Intermediate Frequency (IF) sink pad

IF_AUD_DEC_PAD_OUT

IF-PLL audio output source pad. Contains the audio sampled stream data, usually connected to the bridge bus via an Inter-IC Sound (I2S) bus.

IF_AUD_DEC_PAD_NUM_PADS

Number of pads of the audio IF-PLL.

enum demod_pad_index

analog TV pad index for MEDIA_ENT_F_ATV_DECODER

Constants

DEMOD_PAD_IF_INPUT

IF input sink pad.

DEMOD_PAD_VID_OUT

Video output source pad.

DEMOD_PAD_VBI_OUT

Vertical Blank Interface (VBI) output source pad.

DEMOD_PAD_AUDIO_OUT

Audio output source pad.

DEMOD_NUM_PADS

Maximum number of output pads.

int v4l2_mc_create_media_graph(struct media_device * mdev)

create Media Controller links at the graph.

Parameters

struct media_device * mdev

pointer to the media_device struct.

Description

Add links between the entities commonly found on PC customer’s hardware at the V4L2 side: camera sensors, audio and video PLL-IF decoders, tuners, analog TV decoder and I/O entities (video, VBI and Software Defined Radio).

Note

Webcams are modelled on a very simple way: the sensor is connected directly to the I/O entity. All dirty details, like scaler and crop HW are hidden. While such mapping is enough for v4l2 interface centric PC-consumer’s hardware, V4L2 subdev centric camera hardware should not use this routine, as it will not build the right graph.

int v4l_enable_media_source(struct video_device * vdev)

Hold media source for exclusive use if free

Parameters

struct video_device * vdev

pointer to struct video_device

Description

This interface calls enable_source handler to determine if media source is free for use. The enable_source handler is responsible for checking is the media source is free and start a pipeline between the media source and the media entity associated with the video device. This interface should be called from v4l2-core and dvb-core interfaces that change the source configuration.

Return

returns zero on success or a negative error code.

void v4l_disable_media_source(struct video_device * vdev)

Release media source

Parameters

struct video_device * vdev

pointer to struct video_device

Description

This interface calls disable_source handler to release the media source. The disable_source handler stops the active media pipeline between the media source and the media entity associated with the video device.

Return

returns zero on success or a negative error code.

int v4l2_pipeline_pm_use(struct media_entity * entity, int use)

Update the use count of an entity

Parameters

struct media_entity * entity

The entity

int use

Use (1) or stop using (0) the entity

Description

Update the use count of all entities in the pipeline and power entities on or off accordingly.

This function is intended to be called in video node open (use == 1) and release (use == 0). It uses struct media_entity.use_count to track the power status. The use of this function should be paired with v4l2_pipeline_link_notify().

Return 0 on success or a negative error code on failure. Powering entities off is assumed to never fail. No failure can occur when the use parameter is set to 0.

int v4l2_pipeline_link_notify(struct media_link * link, u32 flags, unsigned int notification)

Link management notification callback

Parameters

struct media_link * link

The link

u32 flags

New link flags that will be applied

unsigned int notification

The link’s state change notification type (MEDIA_DEV_NOTIFY_*)

Description

React to link management on powered pipelines by updating the use count of all entities in the source and sink sides of the link. Entities are powered on or off accordingly. The use of this function should be paired with v4l2_pipeline_pm_use().

Return 0 on success or a negative error code on failure. Powering entities off is assumed to never fail. This function will not fail for disconnection events.