esp-idf/components/esp_rom/include/esp_rom_lldesc.h

/*
 * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#pragma once

#include <stdint.h>
#include "sys/queue.h"

#ifdef __cplusplus
extern "C" {
#endif

/*
 *  SLC2 DMA Desc struct, aka lldesc_t
 *
 * --------------------------------------------------------------
 * | own | EoF | sub_sof | 5'b0   | length [11:0] | size [11:0] |
 * --------------------------------------------------------------
 * |            buf_ptr [31:0]                                  |
 * --------------------------------------------------------------
 * |            next_desc_ptr [31:0]                            |
 * --------------------------------------------------------------
 */

/* this bitfield is start from the LSB!!! */
typedef struct lldesc_s {
    volatile uint32_t size  : 12,
             length: 12,
             offset: 5, /* h/w reserved 5bit, s/w use it as offset in buffer */
             sosf  : 1, /* start of sub-frame */
             eof   : 1, /* end of frame */
             owner : 1; /* hw or sw */
    volatile const uint8_t *buf;       /* point to buffer data */
    union {
        volatile uint32_t empty;
        STAILQ_ENTRY(lldesc_s) qe;  /* pointing to the next desc */
    };
} lldesc_t;

#ifdef __cplusplus
}
#endif