qemu-e2k/include/hw/register.h

/*
 * Register Definition API
 *
 * Copyright (c) 2016 Xilinx Inc.
 * Copyright (c) 2013 Peter Crosthwaite <peter.crosthwaite@xilinx.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 */

#ifndef REGISTER_H
#define REGISTER_H

#include "exec/memory.h"

typedef struct RegisterInfo RegisterInfo;
typedef struct RegisterAccessInfo RegisterAccessInfo;

/**
 * Access description for a register that is part of guest accessible device
 * state.
 *
 * @name: String name of the register
 * @ro: whether or not the bit is read-only
 * @w1c: bits with the common write 1 to clear semantic.
 * @reset: reset value.
 * @cor: Bits that are clear on read
 * @rsvd: Bits that are reserved and should not be changed
 *
 * @pre_write: Pre write callback. Passed the value that's to be written,
 * immediately before the actual write. The returned value is what is written,
 * giving the handler a chance to modify the written value.
 * @post_write: Post write callback. Passed the written value. Most write side
 * effects should be implemented here.
 *
 * @post_read: Post read callback. Passes the value that is about to be returned
 * for a read. The return value from this function is what is ultimately read,
 * allowing this function to modify the value before return to the client.
 */

struct RegisterAccessInfo {
    const char *name;
    uint64_t ro;
    uint64_t w1c;
    uint64_t reset;
    uint64_t cor;
    uint64_t rsvd;
    uint64_t unimp;

    uint64_t (*pre_write)(RegisterInfo *reg, uint64_t val);
    void (*post_write)(RegisterInfo *reg, uint64_t val);

    uint64_t (*post_read)(RegisterInfo *reg, uint64_t val);
};

/**
 * A register that is part of guest accessible state
 * @data: pointer to the register data. Will be cast
 * to the relevant uint type depending on data_size.
 * @data_size: Size of the register in bytes. Must be
 * 1, 2, 4 or 8
 *
 * @access: Access description of this register
 *
 * @debug: Whether or not verbose debug is enabled
 * @prefix: String prefix for log and debug messages
 *
 * @opaque: Opaque data for the register
 */

struct RegisterInfo {
    /* <public> */
    void *data;
    int data_size;

    const RegisterAccessInfo *access;

    void *opaque;
};

/**
 * write a value to a register, subject to its restrictions
 * @reg: register to write to
 * @val: value to write
 * @we: write enable mask
 * @prefix: The device prefix that should be printed before the register name
 * @debug: Should the write operation debug information be printed?
 */

void register_write(RegisterInfo *reg, uint64_t val, uint64_t we,
                    const char *prefix, bool debug);

/**
 * read a value from a register, subject to its restrictions
 * @reg: register to read from
 * @re: read enable mask
 * @prefix: The device prefix that should be printed before the register name
 * @debug: Should the read operation debug information be printed?
 * returns: value read
 */

uint64_t register_read(RegisterInfo *reg, uint64_t re, const char* prefix,
                       bool debug);

/**
 * reset a register
 * @reg: register to reset
 */

void register_reset(RegisterInfo *reg);

#endif