usb(3) - NetBSD Manual Pages

USB(3)                    NetBSD Programmer's Manual                    USB(3)


NAME

     usb, hid_get_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


SYNOPSIS

     #include <usb.h>

     report_desc_t
     hid_get_report_desc(int file);

     void
     hid_dispose_report_desc(report_desc_t d);

     hid_data_t
     hid_start_parse(report_desc_t d, int kindset);

     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 *idp);

     int
     hid_locate(report_desc_t d, u_int usage, hid_kind_t k, hid_item_t *h);

     char *
     hid_usage_page(int i);

     char *
     hid_usage_in_page(u_int u);

     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 usb library provides routines to extract data from USB Human Inter-
     face Devices.

   INTRODUCTION
     USB HID devices send and receive data layed out in a device dependent
     way.  The usb 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.  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.

   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 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 re-
     port 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 <usb.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 stored at idp, otherwise it will contain 0.

     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.  Before either 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 de-
     scriptor 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).


EXAMPLE

     Not yet.


FILES

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


BUGS

     This man page is woefully incomplete.


SEE ALSO

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

     hid(4), usb(4).


HISTORY

     The usb library first appeared in NetBSD 1.5.

NetBSD 1.5                       May 11, 1999                                2