usbhid(3)

NAME

usbhid, hid_get_report_desc, hid_use_report_desc, hid_dispose_report_desc, hid_start_parse, hid_end_parse,

hid_get_item,
hid_report_size, hid_locate, hid_usage_page,

hid_usage_in_page, hid_init, hid_get_data, hid_set_data - USB HID access routines

LIBRARY

library ``libusbhid''

SYNOPSIS

#include <usbhid.h>
report_desc_t
hid_get_report_desc(int file);
report_desc_t
hid_use_report_desc(unsigned char *data, unsigned int size);
void
hid_dispose_report_desc(report_desc_t d);
hid_data_t
hid_start_parse(report_desc_t d, int kindset, int id);
void
hid_end_parse(hid_data_t s);
int
hid_get_item(hid_data_t s, hid_item_t *h);
int
hid_report_size(report_desc_t d, hid_kind_t k, int id);
int
hid_locate(report_desc_t   d,  u_int  usage,  hid_kind_t  k,
hid_item_t *h,
        int id);
char *
hid_usage_page(int i);
char *
hid_usage_in_page(u_int u);
int
hid_parse_usage_page(const char *);
char *
hid_parse_usage_in_page(const char *);
void
hid_init(char *file);
int
hid_get_data(void *data, hid_item_t *h);
void
hid_set_data(void *data, hid_item_t *h, u_int data);

DESCRIPTION

The usbhid library provides routines to extract data from

USB Human
Interface Devices.

Introduction

USB HID devices send and receive data layed out in a device

dependent
way. The usbhid library contains routines to extract the

report
descriptor which contains the data layout information and

then use this
information.

The routines can be divided into four parts: extraction of

the descriptor, parsing of the descriptor, translating to/from symbolic

names, and
data manipulation.

Descriptor Functions

A report descriptor can be obtained by calling

hid_get_report_desc() with
a file descriptor obtained by opening a uhid(4) device. Al

ternatively a
data buffer containing the report descriptor can be passed

into
hid_use_report_desc(). The data is copied into an internal

structure.
When the report descriptor is no longer needed it should be

freed by
calling hid_dispose_report_desc(). The type report_desc_t

is opaque and
should be used when calling the parsing functions. If
hid_dispose_report_desc() fails it will return NULL.

Descriptor Parsing Functions

To parse the report descriptor the hid_start_parse() func

tion should be
called with a report descriptor and a set that describes

which items that
are interesting. The set is obtained by OR-ing together

values (1 << k)
where k is an item of type hid_kind_t. The report ID (if

present) is
given by id. The function returns NULL if the initializa

tion fails, otherwise an opaque value to be used in subsequent calls. Af

ter parsing the
hid_end_parse() function should be called to free internal

data structures.

To iterate through all the items in the report descriptor

hid_get_item()
should be called while it returns a value greater than 0.

When the
report descriptor ends it will returns 0; a syntax error

within the
report descriptor will cause a return value less than 0.

The struct
pointed to by h will be filled with the relevant data for

the item. The
definition of hid_item_t can be found in #include <usbhid.h> and the meaning of the components in the USB HID documenta

tion.

Data should be read/written to the device in the size of the

report. The
size of a report (of a certain kind) can be computed by the
hid_report_size() function. If the report is prefixed by an

ID byte it
is given by id.

To locate a single item the hid_locate() function can be

used. It should
be given the usage code of the item and its kind and it will

fill the
item and return non-zero if the item was found.

Name Translation Functions

The function hid_usage_page() will return the symbolic name

of a usage
page, and the function hid_usage_in_page() will return the

symbolic name
of the usage within the page. Both these functions may re

turn a pointer
to static data.

The functions hid_parse_usage_page() and

hid_parse_usage_in_page() are
the inverses of hid_usage_page() and hid_usage_in_page().

They take a
usage string and return the number of the usage, or -1 if it

cannot be
found.

Before any of these functions can be called the usage table

must be
parsed, this is done by calling hid_init() with the name of

the table.
Passing NULL to this function will cause it to use the de

fault table.

Data Extraction Functions

Given the data obtained from a HID device and an item in the

report
descriptor the hid_get_data() function extracts the value of

the item.
Conversely hid_set_data() can be used to put data into a re

port (which
must be zeroed first).

FILES

/usr/share/misc/usb_hid_usages The default HID usage

table.

EXAMPLES

Not yet.

SEE ALSO

The USB specifications can be found at
http://www.usb.org/developers/docs/.

uhid(4), usb(4)

HISTORY

The usbhid library first appeared in NetBSD 1.5.

BUGS

This man page is woefully incomplete.

BSD December 29, 2001

BSD