Descriptor API

Collaboration diagram for Descriptor API:

Functions
int	a4l_open (a4l_desc_t *dsc, const char *fname)
	Open an Analogy device and basically fill the descriptor. More...
int	a4l_close (a4l_desc_t *dsc)
	Close the Analogy device related with the descriptor. More...
int	a4l_fill_desc (a4l_desc_t *dsc)
	Fill the descriptor with subdevices, channels and ranges data. More...
int	a4l_get_subdinfo (a4l_desc_t *dsc, unsigned int subd, a4l_sbinfo_t **info)
	Get an information structure on a specified subdevice. More...
int	a4l_get_chinfo (a4l_desc_t *dsc, unsigned int subd, unsigned int chan, a4l_chinfo_t **info)
	Get an information structure on a specified channel. More...
int	a4l_get_rnginfo (a4l_desc_t *dsc, unsigned int subd, unsigned int chan, unsigned int rng, a4l_rnginfo_t **info)
	Get an information structure on a specified range. More...

Detailed Description

This is the API interface used to fill and use Analogy device descriptor structure

Function Documentation

a4l_close()

int a4l_close

(

a4l_desc_t *

dsc

)

Close the Analogy device related with the descriptor.

The file descriptor is associated with a context. The context is one of the enabler of asynchronous transfers. So, by closing the file descriptor, the programer must keep in mind that the currently occuring asynchronous transfer will cancelled.

Parameters

[in]

dsc

Device descriptor

Returns

0 on success. Otherwise:

• -EINVAL is returned if some argument is missing or wrong; the the dsc pointer should be checked; check also the kernel log ("dmesg")

References a4l_sys_close(), and a4l_descriptor::fd.

a4l_fill_desc()

int a4l_fill_desc

(

a4l_desc_t *

dsc

)

Fill the descriptor with subdevices, channels and ranges data.

Parameters

[in]

dsc

Device descriptor partly filled by a4l_open().

Returns

0 on success. Otherwise:

• -EINVAL is returned if some argument is missing or wrong; the the dsc pointer should be checked; check also the kernel log ("dmesg")
• -EFAULT is returned if a user <-> kernel transfer went wrong
• -ENODEV is returned if the descriptor is incoherent (the device may be unattached)

References a4l_descriptor::fd, and a4l_descriptor::magic.

a4l_get_chinfo()

int a4l_get_chinfo	(	a4l_desc_t *	dsc,
		unsigned int	subd,
		unsigned int	chan,
		a4l_chinfo_t **	info
	)

Get an information structure on a specified channel.

Parameters

[in]	dsc	Device descriptor filled by a4l_open() and a4l_fill_desc()
[in]	subd	Subdevice index
[in]	chan	Channel index
[out]	info	Channel information structure

Returns

0 on success. Otherwise:

• -EINVAL is returned if some argument is missing or wrong; subd, chan and the dsc pointer should be checked; check also the kernel log ("dmesg"); WARNING: a4l_fill_desc() should be called before using a4l_get_chinfo()

References a4l_descriptor::magic.

a4l_get_rnginfo()

int a4l_get_rnginfo	(	a4l_desc_t *	dsc,
		unsigned int	subd,
		unsigned int	chan,
		unsigned int	rng,
		a4l_rnginfo_t **	info
	)

Get an information structure on a specified range.

Parameters

[in]	dsc	Device descriptor filled by a4l_open() and a4l_fill_desc()
[in]	subd	Subdevice index
[in]	chan	Channel index
[in]	rng	Range index
[out]	info	Range information structure

Returns

0 on success. Otherwise:

• -EINVAL is returned if some argument is missing or wrong; subd, chan, rng and the dsc pointer should be checked; check also the kernel log ("dmesg"); WARNING: a4l_fill_desc() should be called before using a4l_get_rnginfo()

References a4l_descriptor::magic.

a4l_get_subdinfo()

int a4l_get_subdinfo	(	a4l_desc_t *	dsc,
		unsigned int	subd,
		a4l_sbinfo_t **	info
	)

Get an information structure on a specified subdevice.

Parameters

[in]	dsc	Device descriptor filled by a4l_open() and a4l_fill_desc()
[in]	subd	Subdevice index
[out]	info	Subdevice information structure

Returns

0 on success. Otherwise:

• -EINVAL is returned if some argument is missing or wrong; subd and the dsc pointer should be checked; check also the kernel log ("dmesg"); WARNING: a4l_fill_desc() should be called before using a4l_get_subdinfo().

References a4l_descriptor::magic.

Referenced by a4l_sync_dio().

a4l_open()

int a4l_open	(	a4l_desc_t *	dsc,
		const char *	fname
	)

Open an Analogy device and basically fill the descriptor.

Parameters

[out]	dsc	Device descriptor
[in]	fname	Device name

Returns

0 on success. Otherwise:

• -EINVAL is returned if some argument is missing or wrong; the fname and the dsc pointer should be checked; check also the kernel log ("dmesg")
• -EFAULT is returned if a user <-> kernel transfer went wrong

References A4L_BSC_DESC, a4l_sys_close(), a4l_sys_desc(), a4l_sys_open(), and a4l_descriptor::fd.