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USBHID(3) FreeBSD Library Functions Manual USBHID(3)
NAME
usbhid, hid_get_report_desc, hid_get_report_id, 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, hid_get_report, hid_set_report - 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);
int
hid_get_report_id(int file);
int
hid_set_immed(int fd, int enable);
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);
const char *
hid_usage_page(int i);
const char *
hid_usage_in_page(u_int u);
int
hid_parse_usage_page(const char *);
int
hid_parse_usage_in_page(const char *);
void
int
hid_get_report(int fd, enum hid_kind k, unsigned char *data,
unsigned int size);
int
hid_set_report(int fd, enum hid_kind k, unsigned char *data,
unsigned int size);
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.
Synchronous HID operation
Synchronous HID operation can be enabled or disabled by a call to
hid_set_immed(). If the second argument is zero synchronous HID
operation is disabled. Else synchronous HID operation is enabled. The
function returns a negative value on failure.
hid_get_report() and hid_set_report() functions allow to synchronously
get and set specific report if device supports it. For devices with
multiple report IDs, wanted ID should be provided in the first byte of
the buffer for both get and set.
Descriptor Functions
The report descriptor ID can be obtained by calling hid_get_report_id().
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, a set that describes which items that
are interesting, and the desired report ID (or -1 to obtain items of all
report IDs). The set is obtained by OR-ing together values (1 << k)
where k is an item of type hid_kind_t. 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 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
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.
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 report (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.
FreeBSD 14.0-RELEASE-p11 January 27, 2009 FreeBSD 14.0-RELEASE-p11