Subdevice management services

Subdevice declaration in a driver. More...

Functions
struct a4l_subdevice *	a4l_alloc_subd (int sizeof_priv, void(*setup)(struct a4l_subdevice *))
	Allocate a subdevice descriptor.
int	a4l_add_subd (struct a4l_device *dev, struct a4l_subdevice *subd)
	Add a subdevice to the driver descriptor.
struct a4l_subdevice *	a4l_get_subd (struct a4l_device *dev, int idx)
	Get a pointer to the subdevice descriptor referenced by its registration index.

Subdevices types
Flags to define the subdevice type
#define	A4L_SUBD_UNUSED   (A4L_SUBD_MASK_SPECIAL|0x1)
	Unused subdevice.
#define	A4L_SUBD_AI   (A4L_SUBD_MASK_READ|0x2)
	Analog input subdevice.
#define	A4L_SUBD_AO   (A4L_SUBD_MASK_WRITE|0x4)
	Analog output subdevice.
#define	A4L_SUBD_DI   (A4L_SUBD_MASK_READ|0x8)
	Digital input subdevice.
#define	A4L_SUBD_DO   (A4L_SUBD_MASK_WRITE|0x10)
	Digital output subdevice.
#define	A4L_SUBD_DIO   (A4L_SUBD_MASK_SPECIAL|0x20)
	Digital input/output subdevice.
#define	A4L_SUBD_COUNTER   (A4L_SUBD_MASK_SPECIAL|0x40)
	Counter subdevice.
#define	A4L_SUBD_TIMER   (A4L_SUBD_MASK_SPECIAL|0x80)
	Timer subdevice.
#define	A4L_SUBD_MEMORY   (A4L_SUBD_MASK_SPECIAL|0x100)
	Memory, EEPROM, DPRAM.
#define	A4L_SUBD_CALIB   (A4L_SUBD_MASK_SPECIAL|0x200)
	Calibration subdevice DACs.
#define	A4L_SUBD_PROC   (A4L_SUBD_MASK_SPECIAL|0x400)
	Processor, DSP.
#define	A4L_SUBD_SERIAL   (A4L_SUBD_MASK_SPECIAL|0x800)
	Serial IO subdevice.
#define	A4L_SUBD_TYPES
	Mask which gathers all the types.

Subdevice features
Flags to define the subdevice's capabilities
#define	A4L_SUBD_CMD   0x1000
	The subdevice can handle command (i.e it can perform asynchronous acquisition)
#define	A4L_SUBD_MMAP   0x8000
	The subdevice support mmap operations (technically, any driver can do it; however, the developer might want that his driver must be accessed through read / write.

Subdevice status
Flags to define the subdevice's status
#define	A4L_SUBD_BUSY_NR   0
	The subdevice is busy, a synchronous or an asynchronous acquisition is occuring.
#define	A4L_SUBD_BUSY   (1 << A4L_SUBD_BUSY_NR)
	The subdevice is busy, a synchronous or an asynchronous acquisition is occuring.
#define	A4L_SUBD_CLEAN_NR   1
	The subdevice is about to be cleaned in the middle of the detach procedure.
#define	A4L_SUBD_CLEAN   (1 << A4L_SUBD_CLEAN_NR)
	The subdevice is busy, a synchronous or an asynchronous acquisition is occuring.

Detailed Description

Subdevice declaration in a driver.

The subdevice structure is the most complex one in the Analogy driver layer. It contains some description fields to fill and some callbacks to declare.

The description fields are:

• flags: to define the subdevice type and its capabilities;
• chan_desc: to describe the channels which compose the subdevice;
• rng_desc: to declare the usable ranges;

The functions callbakcs are:

• do_cmd() and do_cmdtest(): to performe asynchronous acquisitions thanks to commands;
• cancel(): to abort a working asynchronous acquisition;
• munge(): to apply modifications on the data freshly acquired during an asynchronous transfer. Warning: using this feature with can significantly reduce the performances (if the munge operation is complex, it will trigger high CPU charge and if the acquisition device is DMA capable, many cache-misses and cache-replaces will occur (the benefits of the DMA controller will vanish);
• trigger(): optionnaly to launch an asynchronous acquisition;
• insn_read(), insn_write(), insn_bits(), insn_config(): to perform synchronous acquisition operations.

Once the subdevice is filled, it must be inserted into the driver structure thanks to a4l_add_subd().

Function Documentation

a4l_add_subd()

int a4l_add_subd	(	struct a4l_device *	dev,
		struct a4l_subdevice *	subd
	)

Add a subdevice to the driver descriptor.

Once the driver descriptor structure is initialized, the function a4l_add_subd() must be used so to add some subdevices to the driver.

Parameters

[in]	dev	Device descriptor structure
[in]	subd	Subdevice descriptor structure

Returns

the index with which the subdevice has been registered, in case of error a negative error code is returned.

References a4l_subdevice::dev, a4l_subdevice::idx, and a4l_subdevice::list.

a4l_alloc_subd()

struct a4l_subdevice * a4l_alloc_subd	(	int	sizeof_priv,
		void(*)(struct a4l_subdevice *)	setup
	)

Allocate a subdevice descriptor.

This is a helper function so as to get a suitable subdevice descriptor

Parameters

[in]	sizeof_priv	Size of the subdevice's private data
[in]	setup	Setup function to be called after the allocation

Returns

the index with which the subdevice has been registered, in case of error a negative error code is returned.

References rtdm_malloc().

a4l_get_subd()

struct a4l_subdevice * a4l_get_subd	(	struct a4l_device *	dev,
		int	idx
	)

Get a pointer to the subdevice descriptor referenced by its registration index.

This function is scarcely useful as all the drivers callbacks get the related subdevice descriptor as first argument. This function is not optimized, it goes through a linked list to get the proper pointer. So it must not be used in real-time context but at initialization / cleanup time (attach / detach).

Parameters

[in]	dev	Device descriptor structure
[in]	idx	Subdevice index

Returns

0 on success, otherwise negative error code.