Utility functions

Modules
	utility
	Port connection utility
	Graph Utility
	MMAL to OMX IL conversion utilities
	Rational Utility Functions
Defines
#define	MMAL_OFFSET(TYPE, FIELD)   ((size_t)((uint8_t *)&((TYPE*)0)->FIELD - (uint8_t *)0))
Functions
const char *	mmal_status_to_string (MMAL_STATUS_T status)
uint32_t	mmal_encoding_stride_to_width (uint32_t encoding, uint32_t stride)
uint32_t	mmal_encoding_width_to_stride (uint32_t encoding, uint32_t width)
const char *	mmal_port_type_to_string (MMAL_PORT_TYPE_T type)
MMAL_PARAMETER_HEADER_T *	mmal_port_parameter_alloc_get (MMAL_PORT_T *port, uint32_t id, uint32_t size, MMAL_STATUS_T *status)
void	mmal_port_parameter_free (MMAL_PARAMETER_HEADER_T *param)
void	mmal_buffer_header_copy_header (MMAL_BUFFER_HEADER_T *dest, const MMAL_BUFFER_HEADER_T *src)
MMAL_POOL_T *	mmal_port_pool_create (MMAL_PORT_T *port, unsigned int headers, uint32_t payload_size)
void	mmal_port_pool_destroy (MMAL_PORT_T *port, MMAL_POOL_T *pool)
void	mmal_log_dump_port (MMAL_PORT_T *port)
void	mmal_log_dump_format (MMAL_ES_FORMAT_T *format)
MMAL_PORT_T *	mmal_util_get_port (MMAL_COMPONENT_T *comp, MMAL_PORT_TYPE_T type, unsigned index)
char *	mmal_4cc_to_string (char *buf, size_t len, uint32_t fourcc)

---

Detailed Description

The utility functions provide helpers for common functionality that is not part of the core MMAL API.

---

Define Documentation

#define MMAL_OFFSET	(		TYPE,
			FIELD
	)		((size_t)((uint8_t *)&((TYPE*)0)->FIELD - (uint8_t *)0))

Offset in bytes of FIELD in TYPE.

---

Function Documentation

char* mmal_4cc_to_string	(	char *	buf,
		size_t	len,
		uint32_t	fourcc
	)

Convert a 4cc into a string.

Parameters:

buf	Destination for result
len	Size of result buffer
fourcc	4cc to be converted

Returns:

converted string (buf)

void mmal_buffer_header_copy_header	(	MMAL_BUFFER_HEADER_T *	dest,
		const MMAL_BUFFER_HEADER_T *	src
	)

Copy buffer header metadata from source to destination.

Parameters:

dest	The destination buffer header.
src	The source buffer header.

Copy buffer header metadata from source to dest

uint32_t mmal_encoding_stride_to_width	(	uint32_t	encoding,
		uint32_t	stride
	)

Convert stride to pixel width for a given pixel encoding.

Parameters:

encoding	The pixel encoding (such as one of the pre-defined encodings)
stride	The stride in bytes.

Returns:

The width in pixels.

uint32_t mmal_encoding_width_to_stride	(	uint32_t	encoding,
		uint32_t	width
	)

Convert pixel width to stride for a given pixel encoding

Parameters:

encoding	The pixel encoding (such as one of the pre-defined encodings)
width	The width in pixels.

Returns:

The stride in bytes.

void mmal_log_dump_format

(

MMAL_ES_FORMAT_T *

format

)

Log the content of a MMAL_ES_FORMAT_T structure.

Parameters:

format

Pointer to the format to dump.

void mmal_log_dump_port

(

MMAL_PORT_T *

port

)

Log the content of a MMAL_PORT_T structure.

Parameters:

port	Pointer to the port to dump.

MMAL_PARAMETER_HEADER_T* mmal_port_parameter_alloc_get	(	MMAL_PORT_T *	port,
		uint32_t	id,
		uint32_t	size,
		MMAL_STATUS_T *	status
	)

Get a parameter from a port allocating the required amount of memory for the parameter (i.e. for variable length parameters like URI or arrays). The size field will be set on output to the actual size of the parameter allocated and retrieved.

The pointer returned must be released by a call to mmal_port_parameter_free().

Parameters:

port	port to send request to
id	parameter id
size	initial size hint for allocation (can be 0)
status	status of the parameter get operation (can be 0)

Returns:

pointer to the header of the parameter or NULL on failure.

void mmal_port_parameter_free

(

MMAL_PARAMETER_HEADER_T *

param

)

Free a parameter structure previously allocated via mmal_port_parameter_alloc_get().

Parameters:

param

pointer to header of the parameter

MMAL_POOL_T* mmal_port_pool_create	(	MMAL_PORT_T *	port,
		unsigned int	headers,
		uint32_t	payload_size
	)

Create a pool of MMAL_BUFFER_HEADER_T associated with a specific port. This allows a client to allocate memory for the payload buffers based on the preferences of a port. This for instance will allow the port to allocate memory which can be shared between the host processor and videocore. After allocation, all allocated buffer headers will have been added to the queue.

It is valid to create a pool with no buffer headers, or with zero size payload buffers. The mmal_pool_resize() function can be used to increase or decrease the number of buffer headers, or the size of the payload buffers, after creation of the pool.

Parameters:

port	Port responsible for creating the pool.
headers	Number of buffers which will be allocated with the pool.
payload_size	Size of the payload buffer which will be allocated in each of the buffer headers.

Returns:

Pointer to the newly created pool or NULL on failure.

Create a pool of MMAL_BUFFER_HEADER_T

void mmal_port_pool_destroy	(	MMAL_PORT_T *	port,
		MMAL_POOL_T *	pool
	)

Destroy a pool of MMAL_BUFFER_HEADER_T associated with a specific port. This will also deallocate all of the memory which was allocated when creating or resizing the pool.

Parameters:

port	Pointer to the port responsible for creating the pool.
pool	Pointer to the pool to be destroyed.

Destroy a pool of MMAL_BUFFER_HEADER_T

const char* mmal_port_type_to_string

(

MMAL_PORT_TYPE_T

type

)

Convert a port type to a string.

Parameters:

type	The MMAL port type.

Returns:

A NULL-terminated string describing the port type.

const char* mmal_status_to_string

(

MMAL_STATUS_T

status

)

Convert a status to a statically-allocated string.

Parameters:

status

The MMAL status code.

Returns:

A C string describing the status code.

MMAL_PORT_T* mmal_util_get_port	(	MMAL_COMPONENT_T *	comp,
		MMAL_PORT_TYPE_T	type,
		unsigned	index
	)

Return the nth port.

Parameters:

comp	component to query
index	port index
type	port type

Returns:

port or NULL if not found