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Copyright (c) 1999 Lennart Augustsson <augustss@netbsd.org>
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.Dd May 11, 1999 .Dt USB 3 .Os .Sh NAME .Nm usb , .Nm hid_get_report_desc , .Nm hid_dispose_report_desc , .Nm hid_start_parse , .Nm hid_end_parse , .Nm hid_get_item , .Nm hid_report_size , .Nm hid_locate , .Nm hid_usage_page , .Nm hid_usage_in_page , .Nm hid_init , .Nm hid_get_data , .Nm hid_set_data .Nd USB HID access routines .Sh LIBRARY .Lb libusb .Sh SYNOPSIS .Fd #include <libusb.h> .Ft report_desc_t .Fn hid_get_report_desc "int file" .Ft void .Fn hid_dispose_report_desc "report_desc_t d" .Ft hid_data_t .Fn hid_start_parse "report_desc_t d" "int kindset" .Ft void .Fn hid_end_parse "hid_data_t s" .Ft int .Fn hid_get_item "hid_data_t s" "hid_item_t *h" .Ft int .Fn hid_report_size "report_desc_t d" "hid_kind_t k" "int *idp" .Ft int .Fn hid_locate "report_desc_t d" "u_int usage" "hid_kind_t k" "hid_item_t *h" .Ft char * .Fn hid_usage_page "int i" .Ft char * .Fn hid_usage_in_page "u_int u" .Ft void .Fn hid_init "char *file" .Ft int .Fn hid_get_data "void *data" "hid_item_t *h" .Ft void .Fn hid_set_data "void *data" "hid_item_t *h" "u_int data" .Sh DESCRIPTION The .Nm library provides routines to extract data from USB Human Interface Devices. .Ss INTRODUCTION USB HID devices send and receive data layed out in a device dependent way. The .Nm library contains routines to extract the .Em report descriptor which contains the data layout information and then use this information.
p The routines can be divided into four parts: extraction of the descriptor, parsing of the descriptor, translating to/from symbolic names, and data manipulation. .Ss DESCRIPTOR FUNCTIONS A report descriptor can be obtained by calling .Fn hid_get_report_desc with a file descriptor obtained by opening a .Xr uhid 4 device. When the report descriptor is no longer needed it should be freed by calling .Fn hid_dispose_report_desc . The type .Fa report_desc_t is opaque and should be used when calling the parsing functions. .Ss DESCRIPTOR PARSING FUNCTIONS To parse the report descriptor the .Fn 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 .Fa "(1 << k)" where .Fa k is an item of type .Fa hid_kind_t . The function returns .Fa NULL if the initialization fails, otherwise an opaque value to be used in subsequent calls. After parsing the .Fn hid_end_parse function should be called to free internal data structures.
p To iterate through all the items in the report descriptor .Fn 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 .Fa h will be filled with the relevant data for the item. The definition of .Fa hid_item_t can be found in
a <libusb.h> and the meaning of the components in the USB HID documentation.
p 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 .Fn hid_report_size function. If the report is prefixed by an ID byte it is stored at .Fa idp , otherwise it will contain 0.
p To locate a single item the .Fn 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.
p .Ss NAME TRANSLATION FUNCTIONS The function .Fn hid_usage_page will return the symbolic name of a usage page, and the function .Fn 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 .Fn hid_init with the name of the table. Passing .Fa NULL to this function will cause it to use the default table. .Ss DATA EXTRACTION FUNCTIONS Given the data obtained from a HID device and an item in the report descriptor the .Fn hid_get_data function extracts the value of the item. Conversely .Fn hid_set_data can be used to put data into a report (which must be zeroed first). .Sh EXAMPLE Not yet. .Sh FILES
a /usr/share/misc/usb_hid_usages The default HID usage table. .Sh BUGS This man page is woefully incomplete. .Sh SEE ALSO The .Tn USB specifications can be found at .Dv http://www.usb.org/developers/docs.htm .
p .Xr hid 4 , .Xr usb 4 . .Sh HISTORY The .Nm library first appeared in .Nx 1.5 .