OMAPDSS: Provide an interface for audio support

modelling the hardware overlays, omapdss supports virtual overlays and overlay

managers. These can be used when updating a display with CPU or system DMA.

omapdss driver support for audio

--------------------------------

There exist several display technologies and standards that support audio as

well. Hence, it is relevant to update the DSS device driver to provide an audio

interface that may be used by an audio driver or any other driver interested in

the functionality.

The audio_enable function is intended to prepare the relevant

IP for playback (e.g., enabling an audio FIFO, taking in/out of reset

some IP, enabling companion chips, etc). It is intended to be called before

audio_start. The audio_disable function performs the reverse operation and is

intended to be called after audio_stop.

While a given DSS device driver may support audio, it is possible that for

certain configurations audio is not supported (e.g., an HDMI display using a

VESA video timing). The audio_supported function is intended to query whether

the current configuration of the display supports audio.

The audio_config function is intended to configure all the relevant audio

parameters of the display. In order to make the function independent of any

specific DSS device driver, a struct omap_dss_audio is defined. Its purpose

is to contain all the required parameters for audio configuration. At the

moment, such structure contains pointers to IEC-60958 channel status word

and CEA-861 audio infoframe structures. This should be enough to support

HDMI and DisplayPort, as both are based on CEA-861 and IEC-60958.

The audio_enable/disable, audio_config and audio_supported functions could be

implemented as functions that may sleep. Hence, they should not be called

while holding a spinlock or a readlock.

The audio_start/audio_stop function is intended to effectively start/stop audio

playback after the configuration has taken place. These functions are designed

to be used in an atomic context. Hence, audio_start should return quickly and be

called only after all the needed resources for audio playback (audio FIFOs,

DMA channels, companion chips, etc) have been enabled to begin data transfers.

audio_stop is designed to only stop the audio transfers. The resources used

for playback are released using audio_disable.

The enum omap_dss_audio_state may be used to help the implementations of

the interface to keep track of the audio state. The initial state is _DISABLED;

then, the state transitions to _CONFIGURED, and then, when it is ready to

play audio, to _ENABLED. The state _PLAYING is used when the audio is being

rendered.

Panel and controller drivers

----------------------------

struct omap_dss_device;

struct omap_overlay_manager;

struct snd_aes_iec958;

struct snd_cea_861_aud_if;

enum omap_display_type {

	OMAP_DISPLAY_TYPE_NONE		= 0,

	OMAP_DSS_DISPLAY_SUSPENDED,

};

enum omap_dss_audio_state {

	OMAP_DSS_AUDIO_DISABLED = 0,

	OMAP_DSS_AUDIO_ENABLED,

	OMAP_DSS_AUDIO_CONFIGURED,

	OMAP_DSS_AUDIO_PLAYING,

};

/* XXX perhaps this should be removed */

enum omap_dss_overlay_managers {

	OMAP_DSS_OVL_MGR_LCD,

	enum omap_dss_display_state state;

	enum omap_dss_audio_state audio_state;

	/* platform specific  */

	int (*platform_enable)(struct omap_dss_device *dssdev);

	void (*platform_disable)(struct omap_dss_device *dssdev);

	int hpd_gpio;

};

struct omap_dss_audio {

	struct snd_aes_iec958 *iec;

	struct snd_cea_861_aud_if *cea;

};

struct omap_dss_driver {

	struct device_driver driver;

	int (*read_edid)(struct omap_dss_device *dssdev, u8 *buf, int len);

	bool (*detect)(struct omap_dss_device *dssdev);

	/*

	 * For display drivers that support audio. This encompasses

	 * HDMI and DisplayPort at the moment.

	 */

	/*

	 * Note: These functions might sleep. Do not call while

	 * holding a spinlock/readlock.

	 */

	int (*audio_enable)(struct omap_dss_device *dssdev);

	void (*audio_disable)(struct omap_dss_device *dssdev);

	bool (*audio_supported)(struct omap_dss_device *dssdev);

	int (*audio_config)(struct omap_dss_device *dssdev,

		struct omap_dss_audio *audio);

	/* Note: These functions may not sleep */

	int (*audio_start)(struct omap_dss_device *dssdev);

	void (*audio_stop)(struct omap_dss_device *dssdev);

};

int omap_dss_register_driver(struct omap_dss_driver *);