Tribblix: manual page: usb_parse

USB_PARSE_DATA(9F) Kernel Functions for Drivers USB_PARSE_DATA(9F)

NAME

usb_parse_data - Tokenize and align the bytes of raw variable-format
data

SYNOPSIS

#include <sys/usb/usba.h>

size_t usb_parse_data(char *format, const uchar_t *data,
size_t datalen, void *structure, size_t structlen);

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

format
Null terminated string describing the format of the data
structure for general-purpose byte swapping. The letters
"c," "s," "l," and "L" represent 1, 2, 4 and 8 byte
quantities, respectively. A descriptor that consists of
a short and two bytes would be described by "scc." A
number preceding a letter serves as a multiplier of that
letter. A format equivalent to "scc" is "s2c."

data
Raw descriptor data to parse.

datalen
Length, in bytes, of the raw descriptor data buffer.

structure
Destination data buffer where parsed data is returned.

structlen
Length, in bytes, of the destination data buffer. Parsed
result length will not exceed this value.

DESCRIPTION

The usb_parse_data function parses data such as a variable-format
class- or vendor-specific descriptor. The function also tokenizes and
aligns the bytes of raw descriptor data into fields of a variable-
format descriptor.

While the USBA framework can parse the endpoint, interface,
configuration, and string descriptors defined by the USB 3.0
specification, the format of class- or vendor-specific descriptors
cannot be explicitly defined by the specification and will be unique
for each. The format argument defines how to parse such a descriptor.

While the USB specification defines bit ordering as little-endian,
this routine (like the entire API), converts the data to the
endianness of the host.

The structlen parameter defines the size of the destination data
buffer. Data is truncated to this size if the destination data
buffer is too small.

RETURN VALUES

On success: Returns the size (in bytes) of the parsed data result.

On failure: Returns 0. (Same as USB_PARSE_ERROR).

CONTEXT

May be called from user, kernel or interrupt context.

EXAMPLES

/*
* Parse raw descriptor data in buf, putting result into ret_descr.
* ret_buf_len holds the size of ret_descr buf; routine returns
* number of resulting bytes.
*
* Descriptor being parsed has 2 chars, followed by one short,
* 3 chars and one more short.
*/
size_t size_of_returned_descr;
xxx_descr_t ret_descr;

size_of_returned_descr = usb_parse_data("ccscccs",
buf, sizeof(buf), (void *)ret_descr, (sizeof)xxx_descr_t));
if (size_of_returned_descr < (sizeof (xxx_descr_t))) {
/* Data truncated. */
}

or:

size_of_returned_descr = usb_parse_data("2cs3cs",
buf, sizeof(buf), (void *)ret_descr, (sizeof)xxx_descr_t));
if (size_of_returned_descr < (sizeof (xxx_descr_t))) {
/* Data truncated. */
}

ATTRIBUTES