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
USB Human Interface Devices Library (libusbhid,
-lusbhid)
SYNOPSIS
#include <usbhid.h>
report_desc_t
hid_get_report_desc(
int
file);
report_desc_t
hid_use_report_desc(
const
uint8_t *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(
const
char *file);
int
hid_get_data(
const
void *data,
const
hid_item_t *h);
void
hid_set_data(
void
*data,
const 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 laid 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.
Alternatively 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() function
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 initialization fails, otherwise an opaque value to be used in
subsequent calls. After 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 return 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
<usbhid.h> and the meaning
of the components in the USB HID documentation.
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 return 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
default table.
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
report (which must be zeroed first).
FILES
/usr/share/misc/usb_hid_usages The default HID usage table.
SEE ALSO
uhid(4),
usb(4)
USB Specifications
HISTORY
The
usbhid library first appeared in
NetBSD
1.5 as
usb library and was renamed to
usbhid for
NetBSD 1.6.
BUGS
This man page is woefully incomplete.