|USBHID(3)||Library Functions Manual||USBHID(3)|
— USB HID access routines
char *data, unsigned int
d, int kindset,
d, hid_kind_t k,
d, u_int usage,
const char *
const char *
usbhid library provides routines to
extract data from USB Human Interface Devices.
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.
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
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.
NULL on failure.
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 desired report ID, or -1 to obtain
items of all report IDs, 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
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
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
hid_parse_usage_in_page() are the inverses of
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
the name of the table. Passing NULL to this function
will cause it to use the default table. A return value of -1 indicates that
an error has occurred, and errno is set.
Given the data obtained from a HID device and an item in the
report descriptor the
extracts the value of the item. Conversely
hid_set_data() can be used to put data into a report
(which must be zeroed first).
/usr/share/misc/usb_hid_usages The default HID usage table.
The USB specifications can be found at: http://www.usb.org/developers/docs/
usbhid library first appeared in
This man page is woefully incomplete.
|February 18, 2019||OpenBSD-current|