151 lines
5.6 KiB
C
151 lines
5.6 KiB
C
/****************************************************************************
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* fs/mmap/rammap.h
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*
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* Copyright (C) 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* References: Linux/Documentation/filesystems/romfs.txt
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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#ifndef __FS_MMAP_RAMMAP_H
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#define __FS_MMAP_RAMMAP_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <semaphore.h>
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#ifdef CONFIG_FS_RAMMAP
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Public Types
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****************************************************************************/
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/* This structure describes one file that has been copied to memory and
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* managed as a share-able "memory mapped" file. This functionality is
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* intended to provide a substitute for memory mapped files for architectures
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* that do not have MMUs and, hence, cannot support on demand paging of
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* blocks of a file.
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*
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* This copied file has many of the properties of a standard memory mapped
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* file except:
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*
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* - All of the file must be present in memory. This limits the size of
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* files that may be memory mapped (especially on MCUs with no significant
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* RAM resources).
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* - All mapped files are read-only. You can write to the in-memory image,
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* but the file contents will not change.
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* - There are not access privileges.
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*/
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struct fs_rammap_s
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{
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struct fs_rammap_s *flink; /* Implements a singly linked list */
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FAR void *addr; /* Start of allocated memory */
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size_t length; /* Length of region */
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off_t offset; /* File offset */
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};
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/* This structure defines all "mapped" files */
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struct fs_allmaps_s
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{
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bool initialized; /* True: This structure has been initialized */
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sem_t exclsem; /* Provides exclusive access the list */
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struct fs_rammap_s *head; /* List of mapped files */
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};
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/****************************************************************************
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* Public Variables
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****************************************************************************/
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/* This is the list of all mapped files */
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extern struct fs_allmaps_s g_rammaps;
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Name: rammap_initialize
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*
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* Description:
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* Verified that this capability has been initialized.
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void rammap_initialize(void);
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/****************************************************************************
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* Name: rammmap
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*
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* Description:
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* Support simulation of memory mapped files by copying files into RAM.
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*
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* Parameters:
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* fd file descriptor of the backing file -- required.
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* length The length of the mapping. For exception #1 above, this length
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* ignored: The entire underlying media is always accessible.
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* offset The offset into the file to map
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*
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* Returned Value:
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* On success, rammmap() returns a pointer to the mapped area. On error, the
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* value MAP_FAILED is returned, and errno is set appropriately.
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*
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* EBADF
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* 'fd' is not a valid file descriptor.
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* EINVAL
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* 'length' or 'offset' are invalid
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* ENOMEM
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* Insufficient memory is available to map the file.
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*
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****************************************************************************/
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FAR void *rammap(int fd, size_t length, off_t offset);
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#endif /* CONFIG_FS_RAMMAP */
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#endif /* __FS_MMAP_RAMMAP_H */
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