FreeBSD/Linux Kernel Cross Reference
sys/amd64/include/sf_buf.h

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2003, 2005 Alan L. Cox <alc@cs.rice.edu>
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD$
     */
    
    #ifndef _MACHINE_SF_BUF_H_
    #define _MACHINE_SF_BUF_H_
    
    #ifdef __amd64__
    /*
     * On this machine, the only purpose for which sf_buf is used is to implement
     * an opaque pointer required by the machine-independent parts of the kernel.
     * That pointer references the vm_page that is "mapped" by the sf_buf.  The
     * actual mapping is provided by the direct virtual-to-physical mapping.  
     */
    static inline vm_offset_t
    sf_buf_kva(struct sf_buf *sf)
    {
    
            return (PHYS_TO_DMAP(VM_PAGE_TO_PHYS((vm_page_t)sf)));
    }
    
    static inline vm_page_t
    sf_buf_page(struct sf_buf *sf)
    {
    
            return ((vm_page_t)sf);
    }
    #endif /* __amd64__ */
    #endif /* !_MACHINE_SF_BUF_H_ */

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