Core elements¶
The Industrial I/O core offers both a unified framework for writing drivers for
many different types of embedded sensors and a standard interface to user space
applications manipulating sensors. The implementation can be found under
drivers/iio/industrialio-*
Industrial I/O Devices¶
struct iio_dev
- industrial I/O deviceiio_device_alloc()
- allocate aniio_dev
from a driveriio_device_free()
- free aniio_dev
from a driveriio_device_register()
- register a device with the IIO subsystemiio_device_unregister()
- unregister a device from the IIO subsystem
An IIO device usually corresponds to a single hardware sensor and it provides all the information needed by a driver handling a device. Let’s first have a look at the functionality embedded in an IIO device then we will show how a device driver makes use of an IIO device.
There are two ways for a user space application to interact with an IIO driver.
/sys/bus/iio/iio:deviceX/
, this represents a hardware sensor and groups together the data channels of the same chip./dev/iio:deviceX
, character device node interface used for buffered data transfer and for events information retrieval.
A typical IIO driver will register itself as an I2C or SPI driver and will create two routines, probe and remove.
At probe:
Call
iio_device_alloc()
, which allocates memory for an IIO device.Initialize IIO device fields with driver specific information (e.g. device name, device channels).
Call
iio_device_register()
, this registers the device with the IIO core. After this call the device is ready to accept requests from user space applications.
At remove, we free the resources allocated in probe in reverse order:
iio_device_unregister()
, unregister the device from the IIO core.iio_device_free()
, free the memory allocated for the IIO device.
IIO device sysfs interface¶
Attributes are sysfs files used to expose chip info and also allowing applications to set various configuration parameters. For device with index X, attributes can be found under /sys/bus/iio/iio:deviceX/ directory. Common attributes are:
name
, description of the physical chip.dev
, shows the major:minor pair associated with/dev/iio:deviceX
node.sampling_frequency_available
, available discrete set of sampling frequency values for device.Available standard attributes for IIO devices are described in the
Documentation/ABI/testing/sysfs-bus-iio
file in the Linux kernel sources.
IIO device channels¶
struct iio_chan_spec
- specification of a single channel
An IIO device channel is a representation of a data channel. An IIO device can have one or multiple channels. For example:
a thermometer sensor has one channel representing the temperature measurement.
a light sensor with two channels indicating the measurements in the visible and infrared spectrum.
an accelerometer can have up to 3 channels representing acceleration on X, Y and Z axes.
An IIO channel is described by the struct iio_chan_spec
.
A thermometer driver for the temperature sensor in the example above would
have to describe its channel as follows:
static const struct iio_chan_spec temp_channel[] = {
{
.type = IIO_TEMP,
.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
},
};
Channel sysfs attributes exposed to userspace are specified in the form of bitmasks. Depending on their shared info, attributes can be set in one of the following masks:
info_mask_separate, attributes will be specific to this channel
info_mask_shared_by_type, attributes are shared by all channels of the same type
info_mask_shared_by_dir, attributes are shared by all channels of the same direction
info_mask_shared_by_all, attributes are shared by all channels
When there are multiple data channels per channel type we have two ways to distinguish between them:
set .modified field of
iio_chan_spec
to 1. Modifiers are specified using .channel2 field of the sameiio_chan_spec
structure and are used to indicate a physically unique characteristic of the channel such as its direction or spectral response. For example, a light sensor can have two channels, one for infrared light and one for both infrared and visible light.set .indexed field of
iio_chan_spec
to 1. In this case the channel is simply another instance with an index specified by the .channel field.
Here is how we can make use of the channel’s modifiers:
static const struct iio_chan_spec light_channels[] = {
{
.type = IIO_INTENSITY,
.modified = 1,
.channel2 = IIO_MOD_LIGHT_IR,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
.info_mask_shared = BIT(IIO_CHAN_INFO_SAMP_FREQ),
},
{
.type = IIO_INTENSITY,
.modified = 1,
.channel2 = IIO_MOD_LIGHT_BOTH,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
.info_mask_shared = BIT(IIO_CHAN_INFO_SAMP_FREQ),
},
{
.type = IIO_LIGHT,
.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
.info_mask_shared = BIT(IIO_CHAN_INFO_SAMP_FREQ),
},
}
This channel’s definition will generate two separate sysfs files for raw data retrieval:
/sys/bus/iio/iio:deviceX/in_intensity_ir_raw
/sys/bus/iio/iio:deviceX/in_intensity_both_raw
one file for processed data:
/sys/bus/iio/iio:deviceX/in_illuminance_input
and one shared sysfs file for sampling frequency:
/sys/bus/iio/iio:deviceX/sampling_frequency
.
Here is how we can make use of the channel’s indexing:
static const struct iio_chan_spec light_channels[] = {
{
.type = IIO_VOLTAGE,
.indexed = 1,
.channel = 0,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
},
{
.type = IIO_VOLTAGE,
.indexed = 1,
.channel = 1,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
},
}
This will generate two separate attributes files for raw data retrieval:
/sys/bus/iio/devices/iio:deviceX/in_voltage0_raw
, representing voltage measurement for channel 0./sys/bus/iio/devices/iio:deviceX/in_voltage1_raw
, representing voltage measurement for channel 1.
More details¶
-
struct iio_chan_spec_ext_info¶
Extended channel info attribute
Definition:
struct iio_chan_spec_ext_info {
const char *name;
enum iio_shared_by shared;
ssize_t (*read)(struct iio_dev *, uintptr_t private, struct iio_chan_spec const *, char *buf);
ssize_t (*write)(struct iio_dev *, uintptr_t private,struct iio_chan_spec const *, const char *buf, size_t len);
uintptr_t private;
};
Members
name
Info attribute name
shared
Whether this attribute is shared between all channels.
read
Read callback for this info attribute, may be NULL.
write
Write callback for this info attribute, may be NULL.
private
Data private to the driver.
-
struct iio_enum¶
Enum channel info attribute
Definition:
struct iio_enum {
const char * const *items;
unsigned int num_items;
int (*set)(struct iio_dev *, const struct iio_chan_spec *, unsigned int);
int (*get)(struct iio_dev *, const struct iio_chan_spec *);
};
Members
items
An array of strings.
num_items
Length of the item array.
set
Set callback function, may be NULL.
get
Get callback function, may be NULL.
Description
The iio_enum struct can be used to implement enum style channel attributes. Enum style attributes are those which have a set of strings which map to unsigned integer values. The IIO enum helper code takes care of mapping between value and string as well as generating a “_available” file which contains a list of all available items. The set callback will be called when the attribute is updated. The last parameter is the index to the newly activated item. The get callback will be used to query the currently active item and is supposed to return the index for it.
-
IIO_ENUM¶
IIO_ENUM (_name, _shared, _e)
Initialize enum extended channel attribute
Parameters
_name
Attribute name
_shared
Whether the attribute is shared between all channels
_e
Pointer to an iio_enum struct
Description
This should usually be used together with IIO_ENUM_AVAILABLE()
-
IIO_ENUM_AVAILABLE¶
IIO_ENUM_AVAILABLE (_name, _shared, _e)
Initialize enum available extended channel attribute
Parameters
_name
Attribute name (“_available” will be appended to the name)
_shared
Whether the attribute is shared between all channels
_e
Pointer to an iio_enum struct
Description
Creates a read only attribute which lists all the available enum items in a
space separated list. This should usually be used together with IIO_ENUM()
-
struct iio_mount_matrix¶
iio mounting matrix
Definition:
struct iio_mount_matrix {
const char *rotation[9];
};
Members
rotation
3 dimensional space rotation matrix defining sensor alignment with main hardware
-
IIO_MOUNT_MATRIX¶
IIO_MOUNT_MATRIX (_shared, _get)
Initialize mount matrix extended channel attribute
Parameters
_shared
Whether the attribute is shared between all channels
_get
Pointer to an iio_get_mount_matrix_t accessor
-
struct iio_event_spec¶
specification for a channel event
Definition:
struct iio_event_spec {
enum iio_event_type type;
enum iio_event_direction dir;
unsigned long mask_separate;
unsigned long mask_shared_by_type;
unsigned long mask_shared_by_dir;
unsigned long mask_shared_by_all;
};
Members
type
Type of the event
dir
Direction of the event
mask_separate
Bit mask of enum iio_event_info values. Attributes set in this mask will be registered per channel.
mask_shared_by_type
Bit mask of enum iio_event_info values. Attributes set in this mask will be shared by channel type.
mask_shared_by_dir
Bit mask of enum iio_event_info values. Attributes set in this mask will be shared by channel type and direction.
mask_shared_by_all
Bit mask of enum iio_event_info values. Attributes set in this mask will be shared by all channels.
-
struct iio_chan_spec¶
specification of a single channel
Definition:
struct iio_chan_spec {
enum iio_chan_type type;
int channel;
int channel2;
unsigned long address;
int scan_index;
struct {
char sign;
u8 realbits;
u8 storagebits;
u8 shift;
u8 repeat;
enum iio_endian endianness;
} scan_type;
long info_mask_separate;
long info_mask_separate_available;
long info_mask_shared_by_type;
long info_mask_shared_by_type_available;
long info_mask_shared_by_dir;
long info_mask_shared_by_dir_available;
long info_mask_shared_by_all;
long info_mask_shared_by_all_available;
const struct iio_event_spec *event_spec;
unsigned int num_event_specs;
const struct iio_chan_spec_ext_info *ext_info;
const char *extend_name;
const char *datasheet_name;
unsigned modified:1;
unsigned indexed:1;
unsigned output:1;
unsigned differential:1;
};
Members
type
What type of measurement is the channel making.
channel
What number do we wish to assign the channel.
channel2
If there is a second number for a differential channel then this is it. If modified is set then the value here specifies the modifier.
address
Driver specific identifier.
scan_index
Monotonic index to give ordering in scans when read from a buffer.
scan_type
struct describing the scan type
scan_type.sign
‘s’ or ‘u’ to specify signed or unsigned
scan_type.realbits
Number of valid bits of data
scan_type.storagebits
Realbits + padding
scan_type.shift
Shift right by this before masking out realbits.
scan_type.repeat
Number of times real/storage bits repeats. When the repeat element is more than 1, then the type element in sysfs will show a repeat value. Otherwise, the number of repetitions is omitted.
scan_type.endianness
little or big endian
info_mask_separate
What information is to be exported that is specific to this channel.
info_mask_separate_available
What availability information is to be exported that is specific to this channel.
info_mask_shared_by_type
What information is to be exported that is shared by all channels of the same type.
info_mask_shared_by_type_available
What availability information is to be exported that is shared by all channels of the same type.
info_mask_shared_by_dir
What information is to be exported that is shared by all channels of the same direction.
info_mask_shared_by_dir_available
What availability information is to be exported that is shared by all channels of the same direction.
info_mask_shared_by_all
What information is to be exported that is shared by all channels.
info_mask_shared_by_all_available
What availability information is to be exported that is shared by all channels.
event_spec
Array of events which should be registered for this channel.
num_event_specs
Size of the event_spec array.
ext_info
Array of extended info attributes for this channel. The array is NULL terminated, the last element should have its name field set to NULL.
extend_name
Allows labeling of channel attributes with an informative name. Note this has no effect codes etc, unlike modifiers. This field is deprecated in favour of providing iio_info->read_label() to override the label, which unlike extend_name does not affect sysfs filenames.
datasheet_name
A name used in in-kernel mapping of channels. It should correspond to the first name that the channel is referred to by in the datasheet (e.g. IND), or the nearest possible compound name (e.g. IND-INC).
modified
Does a modifier apply to this channel. What these are depends on the channel type. Modifier is set in channel2. Examples are IIO_MOD_X for axial sensors about the ‘x’ axis.
indexed
Specify the channel has a numerical index. If not, the channel index number will be suppressed for sysfs attributes but not for event codes.
output
Channel is output.
differential
Channel is differential.
-
bool iio_channel_has_info(const struct iio_chan_spec *chan, enum iio_chan_info_enum type)¶
Checks whether a channel supports a info attribute
Parameters
const struct iio_chan_spec *chan
The channel to be queried
enum iio_chan_info_enum type
Type of the info attribute to be checked
Description
Returns true if the channels supports reporting values for the given info attribute type, false otherwise.
-
bool iio_channel_has_available(const struct iio_chan_spec *chan, enum iio_chan_info_enum type)¶
Checks if a channel has an available attribute
Parameters
const struct iio_chan_spec *chan
The channel to be queried
enum iio_chan_info_enum type
Type of the available attribute to be checked
Description
Returns true if the channel supports reporting available values for the given attribute type, false otherwise.
-
struct iio_info¶
constant information about device
Definition:
struct iio_info {
const struct attribute_group *event_attrs;
const struct attribute_group *attrs;
int (*read_raw)(struct iio_dev *indio_dev,struct iio_chan_spec const *chan,int *val,int *val2, long mask);
int (*read_raw_multi)(struct iio_dev *indio_dev,struct iio_chan_spec const *chan,int max_len,int *vals,int *val_len, long mask);
int (*read_avail)(struct iio_dev *indio_dev,struct iio_chan_spec const *chan,const int **vals,int *type,int *length, long mask);
int (*write_raw)(struct iio_dev *indio_dev,struct iio_chan_spec const *chan,int val,int val2, long mask);
int (*read_label)(struct iio_dev *indio_dev,struct iio_chan_spec const *chan, char *label);
int (*write_raw_get_fmt)(struct iio_dev *indio_dev,struct iio_chan_spec const *chan, long mask);
int (*read_event_config)(struct iio_dev *indio_dev,const struct iio_chan_spec *chan,enum iio_event_type type, enum iio_event_direction dir);
int (*write_event_config)(struct iio_dev *indio_dev,const struct iio_chan_spec *chan,enum iio_event_type type,enum iio_event_direction dir, int state);
int (*read_event_value)(struct iio_dev *indio_dev,const struct iio_chan_spec *chan,enum iio_event_type type,enum iio_event_direction dir, enum iio_event_info info, int *val, int *val2);
int (*write_event_value)(struct iio_dev *indio_dev,const struct iio_chan_spec *chan,enum iio_event_type type,enum iio_event_direction dir, enum iio_event_info info, int val, int val2);
int (*read_event_label)(struct iio_dev *indio_dev,struct iio_chan_spec const *chan,enum iio_event_type type,enum iio_event_direction dir, char *label);
int (*validate_trigger)(struct iio_dev *indio_dev, struct iio_trigger *trig);
int (*update_scan_mode)(struct iio_dev *indio_dev, const unsigned long *scan_mask);
int (*debugfs_reg_access)(struct iio_dev *indio_dev,unsigned reg, unsigned writeval, unsigned *readval);
int (*fwnode_xlate)(struct iio_dev *indio_dev, const struct fwnode_reference_args *iiospec);
int (*hwfifo_set_watermark)(struct iio_dev *indio_dev, unsigned val);
int (*hwfifo_flush_to_buffer)(struct iio_dev *indio_dev, unsigned count);
};
Members
event_attrs
event control attributes
attrs
general purpose device attributes
read_raw
function to request a value from the device. mask specifies which value. Note 0 means a reading of the channel in question. Return value will specify the type of value returned by the device. val and val2 will contain the elements making up the returned value.
read_raw_multi
function to return values from the device. mask specifies which value. Note 0 means a reading of the channel in question. Return value will specify the type of value returned by the device. vals pointer contain the elements making up the returned value. max_len specifies maximum number of elements vals pointer can contain. val_len is used to return length of valid elements in vals.
read_avail
function to return the available values from the device. mask specifies which value. Note 0 means the available values for the channel in question. Return value specifies if a IIO_AVAIL_LIST or a IIO_AVAIL_RANGE is returned in vals. The type of the vals are returned in type and the number of vals is returned in length. For ranges, there are always three vals returned; min, step and max. For lists, all possible values are enumerated.
write_raw
function to write a value to the device. Parameters are the same as for read_raw.
read_label
function to request label name for a specified label, for better channel identification.
write_raw_get_fmt
callback function to query the expected format/precision. If not set by the driver, write_raw returns IIO_VAL_INT_PLUS_MICRO.
read_event_config
find out if the event is enabled.
write_event_config
set if the event is enabled.
read_event_value
read a configuration value associated with the event.
write_event_value
write a configuration value for the event.
read_event_label
function to request label name for a specified label, for better event identification.
validate_trigger
function to validate the trigger when the current trigger gets changed.
update_scan_mode
function to configure device and scan buffer when channels have changed
debugfs_reg_access
function to read or write register value of device
fwnode_xlate
fwnode based function pointer to obtain channel specifier index.
hwfifo_set_watermark
function pointer to set the current hardware fifo watermark level; see hwfifo_* entries in Documentation/ABI/testing/sysfs-bus-iio for details on how the hardware fifo operates
hwfifo_flush_to_buffer
function pointer to flush the samples stored in the hardware fifo to the device buffer. The driver should not flush more than count samples. The function must return the number of samples flushed, 0 if no samples were flushed or a negative integer if no samples were flushed and there was an error.
-
struct iio_buffer_setup_ops¶
buffer setup related callbacks
Definition:
struct iio_buffer_setup_ops {
int (*preenable)(struct iio_dev *);
int (*postenable)(struct iio_dev *);
int (*predisable)(struct iio_dev *);
int (*postdisable)(struct iio_dev *);
bool (*validate_scan_mask)(struct iio_dev *indio_dev, const unsigned long *scan_mask);
};
Members
preenable
[DRIVER] function to run prior to marking buffer enabled
postenable
[DRIVER] function to run after marking buffer enabled
predisable
[DRIVER] function to run prior to marking buffer disabled
postdisable
[DRIVER] function to run after marking buffer disabled
validate_scan_mask
[DRIVER] function callback to check whether a given scan mask is valid for the device.
-
struct iio_dev¶
industrial I/O device
Definition:
struct iio_dev {
int modes;
struct device dev;
struct iio_buffer *buffer;
int scan_bytes;
const unsigned long *available_scan_masks;
unsigned masklength;
const unsigned long *active_scan_mask;
bool scan_timestamp;
struct iio_trigger *trig;
struct iio_poll_func *pollfunc;
struct iio_poll_func *pollfunc_event;
struct iio_chan_spec const *channels;
int num_channels;
const char *name;
const char *label;
const struct iio_info *info;
const struct iio_buffer_setup_ops *setup_ops;
void *priv;
};
Members
modes
[DRIVER] bitmask listing all the operating modes supported by the IIO device. This list should be initialized before registering the IIO device. It can also be filed up by the IIO core, as a result of enabling particular features in the driver (see iio_triggered_event_setup()).
dev
[DRIVER] device structure, should be assigned a parent and owner
buffer
[DRIVER] any buffer present
scan_bytes
[INTERN] num bytes captured to be fed to buffer demux
available_scan_masks
[DRIVER] optional array of allowed bitmasks. Sort the array in order of preference, the most preferred masks first.
masklength
[INTERN] the length of the mask established from channels
active_scan_mask
[INTERN] union of all scan masks requested by buffers
scan_timestamp
[INTERN] set if any buffers have requested timestamp
trig
[INTERN] current device trigger (buffer modes)
pollfunc
[DRIVER] function run on trigger being received
pollfunc_event
[DRIVER] function run on events trigger being received
channels
[DRIVER] channel specification structure table
num_channels
[DRIVER] number of channels specified in channels.
name
[DRIVER] name of the device.
label
[DRIVER] unique name to identify which device this is
info
[DRIVER] callbacks and constant info from driver
setup_ops
[DRIVER] callbacks to call before and after buffer enable/disable
priv
[DRIVER] reference to driver’s private information MUST be accessed ONLY via iio_priv() helper
-
iio_device_register¶
iio_device_register (indio_dev)
register a device with the IIO subsystem
Parameters
indio_dev
Device structure filled by the device driver
-
devm_iio_device_register¶
devm_iio_device_register (dev, indio_dev)
Resource-managed
iio_device_register()
Parameters
dev
Device to allocate iio_dev for
indio_dev
Device structure filled by the device driver
Description
Managed iio_device_register. The IIO device registered with this
function is automatically unregistered on driver detach. This function
calls iio_device_register()
internally. Refer to that function for more
information.
Return
0 on success, negative error number on failure.
-
iio_device_claim_direct_scoped¶
iio_device_claim_direct_scoped (fail, iio_dev)
Scoped call to iio_device_claim_direct.
Parameters
fail
What to do on failure to claim device.
iio_dev
Pointer to the IIO devices structure
-
void iio_device_put(struct iio_dev *indio_dev)¶
reference counted deallocation of
struct device
Parameters
struct iio_dev *indio_dev
IIO device structure containing the device
Parameters
struct device *dev
The device embedded in the IIO device
Note
The device must be a IIO device, otherwise the result is undefined.
Parameters
struct iio_dev *indio_dev
IIO device structure
Return
The passed IIO device
-
void iio_device_set_parent(struct iio_dev *indio_dev, struct device *parent)¶
assign parent device to the IIO device object
Parameters
struct iio_dev *indio_dev
IIO device structure
struct device *parent
reference to parent device object
Description
This utility must be called between IIO device allocation
(via devm_iio_device_alloc()
) & IIO device registration
(via iio_device_register()
and devm_iio_device_register()
)).
By default, the device allocation will also assign a parent device to
the IIO device object. In cases where devm_iio_device_alloc()
is used,
sometimes the parent device must be different than the device used to
manage the allocation.
In that case, this helper should be used to change the parent, hence the
requirement to call this between allocation & registration.
Parameters
struct iio_dev *indio_dev
IIO device structure
void *data
Driver specific data
Description
Allows to attach an arbitrary pointer to an IIO device, which can later be
retrieved by iio_device_get_drvdata()
.
Parameters
const struct iio_dev *indio_dev
IIO device structure
Description
Returns the data previously set with iio_device_set_drvdata()
-
struct dentry *iio_get_debugfs_dentry(struct iio_dev *indio_dev)¶
helper function to get the debugfs_dentry
Parameters
struct iio_dev *indio_dev
IIO device structure for device
-
IIO_DEGREE_TO_RAD¶
IIO_DEGREE_TO_RAD (deg)
Convert degree to rad
Parameters
deg
A value in degree
Description
Returns the given value converted from degree to rad
-
IIO_RAD_TO_DEGREE¶
IIO_RAD_TO_DEGREE (rad)
Convert rad to degree
Parameters
rad
A value in rad
Description
Returns the given value converted from rad to degree
-
IIO_G_TO_M_S_2¶
IIO_G_TO_M_S_2 (g)
Convert g to meter / second**2
Parameters
g
A value in g
Description
Returns the given value converted from g to meter / second**2
-
IIO_M_S_2_TO_G¶
IIO_M_S_2_TO_G (ms2)
Convert meter / second**2 to g
Parameters
ms2
A value in meter / second**2
Description
Returns the given value converted from meter / second**2 to g
Parameters
struct iio_dev *indio_dev
Device structure whose ID is being queried
Description
The IIO device ID is a unique index used for example for the naming of the character device /dev/iio:device[ID].
Return
Unique ID for the device.
-
bool iio_buffer_enabled(struct iio_dev *indio_dev)¶
helper function to test if the buffer is enabled
Parameters
struct iio_dev *indio_dev
IIO device structure for device
Return
True, if the buffer is enabled.
-
int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)¶
Set current timestamping clock for the device
Parameters
struct iio_dev *indio_dev
IIO device structure containing the device
clockid_t clock_id
timestamping clock POSIX identifier to set.
Return
0 on success, or a negative error code.
-
clockid_t iio_device_get_clock(const struct iio_dev *indio_dev)¶
Retrieve current timestamping clock for the device
Parameters
const struct iio_dev *indio_dev
IIO device structure containing the device
Return
Clock ID of the current timestamping clock for the device.
-
s64 iio_get_time_ns(const struct iio_dev *indio_dev)¶
utility function to get a time stamp for events etc
Parameters
const struct iio_dev *indio_dev
device
Return
Timestamp of the event in nanoseconds.
-
int iio_read_mount_matrix(struct device *dev, struct iio_mount_matrix *matrix)¶
retrieve iio device mounting matrix from device “mount-matrix” property
Parameters
struct device *dev
device the mounting matrix property is assigned to
struct iio_mount_matrix *matrix
where to store retrieved matrix
Description
If device is assigned no mounting matrix property, a default 3x3 identity matrix will be filled in.
Return
0 if success, or a negative error code on failure.
-
ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)¶
Formats a IIO value into its string representation
Parameters
char *buf
The buffer to which the formatted value gets written which is assumed to be big enough (i.e. PAGE_SIZE).
unsigned int type
One of the IIO_VAL_* constants. This decides how the val and val2 parameters are formatted.
int size
Number of IIO value entries contained in vals
int *vals
Pointer to the values, exact meaning depends on the type parameter.
Return
0 by default, a negative number on failure or the total number of characters written for a type that belongs to the IIO_VAL_* constant.
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int iio_str_to_fixpoint(const char *str, int fract_mult, int *integer, int *fract)¶
Parse a fixed-point number from a string
Parameters
const char *str
The string to parse
int fract_mult
Multiplier for the first decimal place, should be a power of 10
int *integer
The integer part of the number
int *fract
The fractional part of the number
Return
0 on success, or a negative error code if the string could not be parsed.
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struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)¶
allocate an iio_dev from a driver
Parameters
struct device *parent
Parent device.
int sizeof_priv
Space to allocate for private structure.
Return
Pointer to allocated iio_dev on success, NULL on failure.
Parameters
struct iio_dev *dev
the iio_dev associated with the device
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struct iio_dev *devm_iio_device_alloc(struct device *parent, int sizeof_priv)¶
Resource-managed
iio_device_alloc()
Parameters
struct device *parent
Device to allocate iio_dev for, and parent for this IIO device
int sizeof_priv
Space to allocate for private structure.
Description
Managed iio_device_alloc. iio_dev allocated with this function is automatically freed on driver detach.
Return
Pointer to allocated iio_dev on success, NULL on failure.
Parameters
struct iio_dev *indio_dev
Device structure representing the device.
Parameters
struct iio_dev *indio_dev
the iio_dev associated with the device
Description
If the device is in direct mode it is guaranteed to stay
that way until iio_device_release_direct_mode()
is called.
Use with iio_device_release_direct_mode()
Return
0 on success, -EBUSY on failure.
Parameters
struct iio_dev *indio_dev
the iio_dev associated with the device
Description
Release the claim. Device is no longer guaranteed to stay in direct mode.
Use with iio_device_claim_direct_mode()
Parameters
struct iio_dev *indio_dev
the iio_dev associated with the device
Description
If the device is in buffer mode it is guaranteed to stay
that way until iio_device_release_buffer_mode()
is called.
Use with iio_device_release_buffer_mode()
.
Return
0 on success, -EBUSY on failure.
Parameters
struct iio_dev *indio_dev
the iio_dev associated with the device
Description
Release the claim. Device is no longer guaranteed to stay in buffer mode.
Use with iio_device_claim_buffer_mode()
.
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int iio_device_get_current_mode(struct iio_dev *indio_dev)¶
helper function providing read-only access to the opaque currentmode variable
Parameters
struct iio_dev *indio_dev
IIO device structure for device