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/*************************************************************************** |
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* Copyright (c) 2024 Microsoft Corporation |
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* |
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* This program and the accompanying materials are made available under the |
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* terms of the MIT License which is available at |
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* https://opensource.org/licenses/MIT. |
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* |
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* SPDX-License-Identifier: MIT |
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**************************************************************************/ |
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/**************************************************************************/ |
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/**************************************************************************/ |
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/** */ |
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/** USBX Component */ |
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/** */ |
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/** HID Class */ |
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/** */ |
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/**************************************************************************/ |
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/**************************************************************************/ |
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/* Include necessary system files. */ |
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#define UX_SOURCE_CODE |
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#include "ux_api.h" |
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#include "ux_host_class_hid.h" |
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#include "ux_host_stack.h" |
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/**************************************************************************/ |
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/* */ |
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/* FUNCTION RELEASE */ |
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/* */ |
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/* _ux_host_class_hid_field_decompress PORTABLE C */ |
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/* 6.3.0 */ |
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/* AUTHOR */ |
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/* */ |
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/* Chaoqiong Xiao, Microsoft Corporation */ |
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/* */ |
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/* DESCRIPTION */ |
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/* */ |
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/* This function will decompress a field and return the usage/value. */ |
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/* */ |
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/* INPUT */ |
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/* */ |
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/* hid_field Pointer to HID field */ |
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/* report_buffer Pointer to report buffer */ |
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/* client_report Pointer to client report */ |
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/* */ |
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/* OUTPUT */ |
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/* */ |
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/* Completion Status */ |
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/* */ |
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/* CALLS */ |
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/* */ |
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/* None */ |
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/* */ |
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/* CALLED BY */ |
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/* */ |
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/* HID Class */ |
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/* */ |
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/* RELEASE HISTORY */ |
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/* */ |
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/* DATE NAME DESCRIPTION */ |
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/* */ |
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/* 05-19-2020 Chaoqiong Xiao Initial Version 6.0 */ |
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/* 09-30-2020 Chaoqiong Xiao Modified comment(s), */ |
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/* resulting in version 6.1 */ |
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/* 10-31-2023 Chaoqiong Xiao Modified comment(s), */ |
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/* improved usage handling, */ |
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/* resulting in version 6.3.0 */ |
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/* */ |
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/**************************************************************************/ |
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UINT _ux_host_class_hid_field_decompress(UX_HOST_CLASS_HID_FIELD *hid_field, UCHAR *report_buffer, UX_HOST_CLASS_HID_CLIENT_REPORT *client_report) |
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{ |
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ULONG field_report_count; |
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ULONG field_report_size; |
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ULONG data_offset_byte; |
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ULONG data_offset_bit; |
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ULONG data_offset_bit_in_report; |
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ULONG field_value; |
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ULONG field_value_bit_shifting; |
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ULONG field_usage; |
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ULONG report_content; |
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/* Calculate the address of the beginning of the field in the report. */ |
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data_offset_byte = (hid_field -> ux_host_class_hid_field_report_offset >> 3); |
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/* Calculate the bit start address. Hopefully things will be on a boundary but not necessary. */ |
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data_offset_bit = hid_field -> ux_host_class_hid_field_report_offset & 7; |
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/* Each report field has a report_count value. This count is used to extract values from the |
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incoming report and build each usage/value instance. */ |
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✓✓ |
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for (field_report_count = 0; field_report_count < hid_field -> ux_host_class_hid_field_report_count; field_report_count++) |
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{ |
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/* Get the report size in bits. */ |
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field_report_size = hid_field -> ux_host_class_hid_field_report_size; |
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/* We use the bit offset for this report and not the generic field bit offset. */ |
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data_offset_bit_in_report = data_offset_bit; |
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/* Reset the local value. */ |
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field_value = 0; |
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/* And start with bit 0 in the target value. */ |
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field_value_bit_shifting = 0; |
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/* Build the value field bit by bit. */ |
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✓✓ |
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while (field_report_size-- != 0) |
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{ |
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/* Read the content. This method is redundant if we are not changing byte but it |
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makes the algorithm much easier. */ |
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report_content = (ULONG) *(report_buffer + data_offset_byte + (data_offset_bit_in_report >> 3)); |
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/* Shift the current value content to allow space to store the new bit. */ |
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field_value |= ((report_content >> (data_offset_bit_in_report & 7)) & 1) << field_value_bit_shifting; |
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/* Move to next bit in the report. */ |
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data_offset_bit_in_report++; |
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/* And the next bit in the value. */ |
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field_value_bit_shifting++; |
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} |
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/* The Usage value will depend if the data is defined as a variable or an array in the HID report. */ |
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✓✓ |
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if (hid_field -> ux_host_class_hid_field_value & UX_HOST_CLASS_HID_ITEM_VARIABLE) |
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{ |
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/* Take the usage directly from the usage array (if specified). */ |
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✓✓ |
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if (hid_field -> ux_host_class_hid_field_usages) |
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field_usage = *(hid_field -> ux_host_class_hid_field_usages + field_report_count); |
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else |
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field_usage = 0; |
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} |
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else |
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{ |
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/* This is an array, so compute the usage from the min value, the report count and the |
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computed report value. */ |
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field_usage = hid_field -> ux_host_class_hid_field_usage_min + (ULONG)((SLONG)field_value - hid_field -> ux_host_class_hid_field_logical_min); |
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/* Also add the usage page. */ |
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field_usage |= (hid_field -> ux_host_class_hid_field_usage_page << 16); |
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} |
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/* Put the value and the usage into the caller's buffer. */ |
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*(client_report -> ux_host_class_hid_client_report_buffer + client_report -> ux_host_class_hid_client_report_actual_length) = field_usage; |
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client_report -> ux_host_class_hid_client_report_actual_length++; |
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*(client_report -> ux_host_class_hid_client_report_buffer + client_report -> ux_host_class_hid_client_report_actual_length) = field_value; |
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client_report -> ux_host_class_hid_client_report_actual_length++; |
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/* Calculate the next address for this field. */ |
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data_offset_bit += hid_field -> ux_host_class_hid_field_report_size; |
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} |
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/* Return successful completion. */ |
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return(UX_SUCCESS); |
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} |
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