source: mainline/uspace/lib/usbdev/src/dp.c@ 9bfa8c8

/*
 * SPDX-FileCopyrightText: 2011 Vojtech Horky
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

/** @addtogroup libusbdev
 * @{
 */
/**
 * @file
 * USB descriptor parser (implementation).
 *
 * The descriptor parser is a generic parser for structure, where individual
 * items are stored in single buffer and each item begins with length followed
 * by type. These types are organized into tree hierarchy.
 *
 * The parser is able of only two actions: find first child and find next
 * sibling.
 */
#include <usb/dev/dp.h>
#include <usb/descriptor.h>

#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#define NESTING(parentname, childname) \
        { \
                .child = USB_DESCTYPE_##childname, \
                .parent = USB_DESCTYPE_##parentname, \
        }
#define LAST_NESTING { -1, -1 }

/** Nesting of standard USB descriptors. */
const usb_dp_descriptor_nesting_t usb_dp_standard_descriptor_nesting[] = {
        NESTING(CONFIGURATION, INTERFACE),
        NESTING(INTERFACE, ENDPOINT),
        NESTING(ENDPOINT, SSPEED_EP_COMPANION),
        NESTING(INTERFACE, HUB),
        NESTING(INTERFACE, HID),
        NESTING(HID, HID_REPORT),
        LAST_NESTING
};

#undef NESTING
#undef LAST_NESTING

/** Tells whether pointer points inside descriptor data.
 *
 * @param data Parser data.
 * @param ptr Pointer to be verified.
 * @return Whether @p ptr points inside <code>data->data</code> field.
 */
static bool is_valid_descriptor_pointer(const usb_dp_parser_data_t *data,
    const uint8_t *ptr)
{
        if (ptr == NULL) {
                return false;
        }

        if (ptr < data->data) {
                return false;
        }

        if ((size_t)(ptr - data->data) >= data->size) {
                return false;
        }

        return true;
}

/** Get next descriptor regardless of the nesting.
 *
 * @param data Parser data.
 * @param current Pointer to current descriptor.
 * @return Pointer to start of next descriptor.
 * @retval NULL Invalid input or no next descriptor.
 */
static const uint8_t *get_next_descriptor(const usb_dp_parser_data_t *data,
    const uint8_t *current)
{
        assert(is_valid_descriptor_pointer(data, current));

        const uint8_t current_length = *current;
        const uint8_t *next = current + current_length;

        if (!is_valid_descriptor_pointer(data, next)) {
                return NULL;
        }

        return next;
}

/** Get descriptor type.
 *
 * @see usb_descriptor_type_t
 *
 * @param data Parser data.
 * @param start Pointer to start of the descriptor.
 * @return Descriptor type.
 * @retval -1 Invalid input.
 */
static int get_descriptor_type(const usb_dp_parser_data_t *data,
    const uint8_t *start)
{
        if (start == NULL) {
                return -1;
        }

        start++;
        if (!is_valid_descriptor_pointer(data, start)) {
                return -1;
        } else {
                return (int) (*start);
        }
}

/** Tells whether descriptors could be nested.
 *
 * @param parser Parser.
 * @param child Child descriptor type.
 * @param parent Parent descriptor type.
 * @return Whether @p child could be child of @p parent.
 */
static bool is_nested_descriptor_type(const usb_dp_parser_t *parser,
    int child, int parent)
{
        const usb_dp_descriptor_nesting_t *nesting = parser->nesting;
        while ((nesting->child > 0) && (nesting->parent > 0)) {
                if ((nesting->child == child) && (nesting->parent == parent)) {
                        return true;
                }
                nesting++;
        }
        return false;
}

/** Tells whether descriptors could be nested.
 *
 * @param parser Parser.
 * @param data Parser data.
 * @param child Pointer to child descriptor.
 * @param parent Pointer to parent descriptor.
 * @return Whether @p child could be child of @p parent.
 */
static bool is_nested_descriptor(const usb_dp_parser_t *parser,
    const usb_dp_parser_data_t *data, const uint8_t *child, const uint8_t *parent)
{
        return is_nested_descriptor_type(parser,
            get_descriptor_type(data, child),
            get_descriptor_type(data, parent));
}

/** Find first nested descriptor of given parent.
 *
 * @param parser Parser.
 * @param data Parser data.
 * @param parent Pointer to the beginning of parent descriptor.
 * @return Pointer to the beginning of the first nested (child) descriptor.
 * @retval NULL No child descriptor found.
 * @retval NULL Invalid input.
 */
const uint8_t *usb_dp_get_nested_descriptor(const usb_dp_parser_t *parser,
    const usb_dp_parser_data_t *data, const uint8_t *parent)
{
        if (!is_valid_descriptor_pointer(data, parent)) {
                return NULL;
        }

        const uint8_t *next = get_next_descriptor(data, parent);
        if (next == NULL) {
                return NULL;
        }

        if (is_nested_descriptor(parser, data, next, parent)) {
                return next;
        } else {
                return NULL;
        }
}

/** Skip all nested descriptors.
 *
 * @param parser Parser.
 * @param data Parser data.
 * @param parent Pointer to the beginning of parent descriptor.
 * @return Pointer to first non-child descriptor.
 * @retval NULL No next descriptor.
 * @retval NULL Invalid input.
 */
static const uint8_t *skip_nested_descriptors(const usb_dp_parser_t *parser,
    const usb_dp_parser_data_t *data, const uint8_t *parent)
{
        const uint8_t *child =
            usb_dp_get_nested_descriptor(parser, data, parent);
        if (child == NULL) {
                return get_next_descriptor(data, parent);
        }
        const uint8_t *next_child =
            skip_nested_descriptors(parser, data, child);
        while (is_nested_descriptor(parser, data, next_child, parent)) {
                next_child = skip_nested_descriptors(parser, data, next_child);
        }

        return next_child;
}

/** Get sibling descriptor.
 *
 * @param parser Parser.
 * @param data Parser data.
 * @param parent Pointer to common parent descriptor.
 * @param sibling Left sibling.
 * @return Pointer to first right sibling of @p sibling.
 * @retval NULL No sibling exist.
 * @retval NULL Invalid input.
 */
const uint8_t *usb_dp_get_sibling_descriptor(
    const usb_dp_parser_t *parser, const usb_dp_parser_data_t *data,
    const uint8_t *parent, const uint8_t *sibling)
{
        if (!is_valid_descriptor_pointer(data, parent) ||
            !is_valid_descriptor_pointer(data, sibling)) {
                return NULL;
        }

        const uint8_t *possible_sibling =
            skip_nested_descriptors(parser, data, sibling);
        if (possible_sibling == NULL) {
                return NULL;
        }

        int parent_type = get_descriptor_type(data, parent);
        int possible_sibling_type = get_descriptor_type(data, possible_sibling);
        if (is_nested_descriptor_type(parser,
            possible_sibling_type, parent_type)) {
                return possible_sibling;
        } else {
                return NULL;
        }
}

/** Browser of the descriptor tree.
 *
 * @see usb_dp_walk_simple
 *
 * @param parser Descriptor parser.
 * @param data Data for descriptor parser.
 * @param root Pointer to current root of the tree.
 * @param depth Current nesting depth.
 * @param callback Callback for each found descriptor.
 * @param arg Custom (user) argument.
 */
static void usb_dp_browse_simple_internal(const usb_dp_parser_t *parser,
    const usb_dp_parser_data_t *data, const uint8_t *root, size_t depth,
    void (*callback)(const uint8_t *, size_t, void *), void *arg)
{
        if (root == NULL) {
                return;
        }
        callback(root, depth, arg);
        const uint8_t *child = usb_dp_get_nested_descriptor(parser, data, root);
        do {
                usb_dp_browse_simple_internal(parser, data, child, depth + 1,
                    callback, arg);
                child = usb_dp_get_sibling_descriptor(parser, data,
                    root, child);
        } while (child != NULL);
}

/** Browse flatten descriptor tree.
 *
 * The callback is called with following arguments: pointer to the start
 * of the descriptor (somewhere inside @p descriptors), depth of the nesting
 * (starting from 0 for the first descriptor) and the custom argument.
 * Note that the size of the descriptor is not passed because it can
 * be read from the first byte of the descriptor.
 *
 * @param descriptors Descriptor data.
 * @param descriptors_size Size of descriptor data (in bytes).
 * @param descriptor_nesting Possible descriptor nesting.
 * @param callback Callback for each found descriptor.
 * @param arg Custom (user) argument.
 */
void usb_dp_walk_simple(const uint8_t *descriptors, size_t descriptors_size,
    const usb_dp_descriptor_nesting_t *descriptor_nesting,
    walk_callback_t callback, void *arg)
{
        if ((descriptors == NULL) || (descriptors_size == 0) ||
            (descriptor_nesting == NULL) || (callback == NULL)) {
                return;
        }

        const usb_dp_parser_data_t data = {
                .data = descriptors,
                .size = descriptors_size,
                .arg = NULL
        };

        const usb_dp_parser_t parser = {
                .nesting = descriptor_nesting
        };

        usb_dp_browse_simple_internal(&parser, &data, descriptors,
            0, callback, arg);
}

/** @}
 */