usbhid(3) - NetBSD Manual Pages

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USBHID(3)               NetBSD Library Functions Manual              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_parse_usage_page, hid_parse_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 *);

     int
     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 descrip-
     tor, 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, oth-
     erwise an opaque value to be used in subsequent calls.  After parsing the
     hid_end_parse() function should be called to free internal data struc-
     tures.

     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 compo-
     nents 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.

   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.


SEE ALSO

     uhid(4), usb(4)

     USB Specifications:
           http://www.usb.org/developers/docs/


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.

NetBSD 10.1                      May 21, 2022                      NetBSD 10.1