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106 lines
4.0 KiB
C
106 lines
4.0 KiB
C
/******************************************************************************
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* *
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* License Agreement *
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* *
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* Copyright (c) 2004 Altera Corporation, San Jose, California, USA. *
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* All rights reserved. *
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* *
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* Permission is hereby granted, free of charge, to any person obtaining a *
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* copy of this software and associated documentation files (the "Software"), *
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* to deal in the Software without restriction, including without limitation *
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* the rights to use, copy, modify, merge, publish, distribute, sublicense, *
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* and/or sell copies of the Software, and to permit persons to whom the *
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* Software is furnished to do so, subject to the following conditions: *
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* *
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* The above copyright notice and this permission notice shall be included in *
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* all copies or substantial portions of the Software. *
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* *
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE *
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER *
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING *
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER *
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* DEALINGS IN THE SOFTWARE. *
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* *
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* This agreement shall be governed in all respects by the laws of the State *
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* of California and by the laws of the United States of America. *
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* *
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* Altera does not recommend, suggest or require that this reference design *
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* file be used in conjunction or combination with any other product. *
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******************************************************************************/
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#include <stddef.h>
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#include <stdio.h>
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#include <errno.h>
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#include "sys/alt_dev.h"
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#include "priv/alt_file.h"
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#include "alt_types.h"
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#include "system.h"
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/*
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* alt_get_fd() is called to allocate a new file descriptor from the file
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* descriptor pool. If a file descriptor is succesfully allocated, it is
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* configured to refer to device "dev".
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*
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* The return value is the index of the file descriptor structure (i.e.
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* the offset of the file descriptor within the file descriptor array). A
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* negative value indicates failure.
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*/
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int alt_get_fd (alt_dev* dev)
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{
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alt_32 i;
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int rc = -EMFILE;
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/*
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* Take the alt_fd_list_lock semaphore in order to avoid races when
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* accessing the file descriptor pool.
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*/
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ALT_SEM_PEND(alt_fd_list_lock, 0);
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/*
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* Search through the list of file descriptors, and allocate the first
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* free descriptor that's found.
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*
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* If a free descriptor is found, then the value of "alt_max_fd" is
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* updated accordingly. "alt_max_fd" is a 'highwater mark' which
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* indicates the highest file descriptor ever allocated. This is used to
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* improve efficency when searching the file descriptor list, and
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* therefore reduce contention on the alt_fd_list_lock semaphore.
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*/
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for (i = 0; i < ALT_MAX_FD; i++)
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{
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if (!alt_fd_list[i].dev)
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{
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alt_fd_list[i].dev = dev;
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if (i > alt_max_fd)
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{
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alt_max_fd = i;
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}
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rc = i;
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goto alt_get_fd_exit;
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}
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}
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alt_get_fd_exit:
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/*
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* Release the alt_fd_list_lock semaphore now that we are done with the
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* file descriptor pool.
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*/
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ALT_SEM_POST(alt_fd_list_lock);
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return rc;
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}
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