Synchronous acquisition API
[Level 2 API]

Collaboration diagram for Synchronous acquisition API:

Functions
int	a4l_sync_write (a4l_desc_t *dsc, unsigned int idx_subd, unsigned int chan_desc, unsigned int ns_delay, void *buf, size_t nbyte)
	Perform a synchronous acquisition write operation.
int	a4l_sync_read (a4l_desc_t *dsc, unsigned int idx_subd, unsigned int chan_desc, unsigned int ns_delay, void *buf, size_t nbyte)
	Perform a synchronous acquisition read operation.
int	a4l_sync_dio (a4l_desc_t *dsc, unsigned int idx_subd, void *mask, void *buf)
	Perform a synchronous acquisition digital acquisition.
int	a4l_config_subd (a4l_desc_t *dsc, unsigned int idx_subd, unsigned int type,...)
	Configure a subdevice.

---

Function Documentation

int a4l_config_subd	(	a4l_desc_t *	dsc,
		unsigned int	idx_subd,
		unsigned int	type,
			...
	)

Configure a subdevice.

a4l_config_subd() takes a variable count of arguments. According to the configuration type, some additional argument is necessary:

• A4L_INSN_CONFIG_DIO_INPUT: the channel index (unsigned int)
• A4L_INSN_CONFIG_DIO_OUTPUT: the channel index (unsigned int)
• A4L_INSN_CONFIG_DIO_QUERY: the returned DIO polarity (unsigned int *)

Parameters:

[in]	dsc	Device descriptor filled by a4l_open() (and optionally a4l_fill_desc())
[in]	idx_subd	Index of the concerned subdevice
[in]	type	Configuration parameter

Returns:

0 on success. Otherwise:

• -EINVAL is returned if some argument is missing or wrong (Please, type "dmesg" for more info)
• -ENOSYS is returned if the configuration parameter is not supported

References A4L_INSN_CONFIG, a4l_snd_insn(), CHAN, a4l_instruction::chan_desc, and a4l_instruction::data_size.

int a4l_sync_dio	(	a4l_desc_t *	dsc,
		unsigned int	idx_subd,
		void *	mask,
		void *	buf
	)

Perform a synchronous acquisition digital acquisition.

Parameters:

[in]	dsc	Device descriptor filled by a4l_open() (and optionally a4l_fill_desc())
[in]	idx_subd	Index of the concerned subdevice
[in]	mask	Write mask which indicates which bit(s) must be modified
[in,out]	buf	Input / output buffer

Returns:

Number of bytes read, otherwise negative error code:

• -EINVAL is returned if some argument is missing or wrong (Please, type "dmesg" for more info)
• -EFAULT is returned if a user <-> kernel transfer went wrong
• -ENOMEM is returned if the system is out of memory
• -ENOSYS is returned if the driver does not provide any handler "instruction bits"

References a4l_get_subdinfo(), A4L_INSN_BITS, a4l_sizeof_subd(), a4l_snd_insn(), and a4l_instruction::data_size.

int a4l_sync_read	(	a4l_desc_t *	dsc,
		unsigned int	idx_subd,
		unsigned int	chan_desc,
		unsigned int	ns_delay,
		void *	buf,
		size_t	nbyte
	)

Perform a synchronous acquisition read operation.

Parameters:

[in]	dsc	Device descriptor filled by a4l_open() (and optionally a4l_fill_desc())
[in]	idx_subd	Index of the concerned subdevice
[in]	chan_desc	Channel descriptor (channel, range and reference)
[in]	ns_delay	Optional delay (in nanoseconds) to wait between the setting of the input channel and sample(s) acquisition(s).
[in]	buf	Input buffer
[in]	nbyte	Number of bytes to read

Returns:

Number of bytes read, otherwise negative error code:

• -EINVAL is returned if some argument is missing or wrong (Please, type "dmesg" for more info)
• -EFAULT is returned if a user <-> kernel transfer went wrong
• -ENOMEM is returned if the system is out of memory

References A4L_INSN_READ, A4L_INSN_WAIT, a4l_snd_insn(), a4l_snd_insnlist(), a4l_instruction::data, and a4l_instruction::data_size.

int a4l_sync_write	(	a4l_desc_t *	dsc,
		unsigned int	idx_subd,
		unsigned int	chan_desc,
		unsigned int	ns_delay,
		void *	buf,
		size_t	nbyte
	)

Perform a synchronous acquisition write operation.

Parameters:

[in]	dsc	Device descriptor filled by a4l_open() (and optionally a4l_fill_desc())
[in]	idx_subd	Index of the concerned subdevice
[in]	chan_desc	Channel descriptor (channel, range and reference)
[in]	ns_delay	Optional delay (in nanoseconds) to wait between the setting of the input channel and sample(s) acquisition(s).
[in]	buf	Output buffer
[in]	nbyte	Number of bytes to write

Returns:

Number of bytes written, otherwise negative error code:

• -EINVAL is returned if some argument is missing or wrong (Please, type "dmesg" for more info)
• -EFAULT is returned if a user <-> kernel transfer went wrong
• -ENOMEM is returned if the system is out of memory

References A4L_INSN_WAIT, A4L_INSN_WRITE, a4l_snd_insn(), a4l_snd_insnlist(), a4l_instruction::data, and a4l_instruction::data_size.