243da80fc6
an initial release. Primary remaining problem: udev-style kernels don't allow registration of a preexisting class right now. This will need to be fixed semi-immediately. git-svn-id: http://svn.xiph.org/trunk/fusd@12316 0101bb08-14d6-0310-b084-bc0e0c8e3800
125 lines
3.6 KiB
C
125 lines
3.6 KiB
C
/*
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*
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* Copyright (c) 2003 The Regents of the University of California. All
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* rights reserved.
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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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* - 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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*
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* - Neither the name of the University nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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/*
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* FUSD - The Framework for UserSpace Devices - Example program
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*
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* Jeremy Elson <jelson@circlemud.org>
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*
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* echo.c: Example of how to use both the 'read' and 'write' callbacks.
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*
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* This example creates a single device, /dev/echo. If you write
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* something to /dev/echo (e.g., "echo HI THERE > /dev/echo"), it gets
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* stored. Then, when you read (e.g. "cat /dev/echo"), you get back
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* whatever you wrote most recently.
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*
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* $Id$
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include "fusd.h"
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#define MIN(x, y) ((x) < (y) ? (x) : (y))
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/* EXAMPLE START echo.c */
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char *data = NULL;
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int data_length = 0;
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ssize_t echo_read(struct fusd_file_info *file, char *user_buffer,
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size_t user_length, loff_t *offset)
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{
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/* if the user has read past the end of the data, return EOF */
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if (*offset >= data_length)
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return 0;
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/* only return as much data as we have */
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user_length = MIN(user_length, data_length - *offset);
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/* copy data to user starting from the first byte they haven't seen */
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memcpy(user_buffer, data + *offset, user_length);
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*offset += user_length;
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/* tell them how much data they got */
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return user_length;
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}
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ssize_t echo_write(struct fusd_file_info *file, const char *user_buffer,
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size_t user_length, loff_t *offset)
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{
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/* free the old data, if any */
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if (data != NULL) {
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free(data);
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data = NULL;
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data_length = 0;
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}
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/* allocate space for new data; return error if that fails */
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if ((data = malloc(user_length)) == NULL)
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return -ENOMEM;
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/* make a copy of user's data; tell the user we copied everything */
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memcpy(data, user_buffer, user_length);
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data_length = user_length;
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return user_length;
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}
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/* EXAMPLE STOP */
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int do_open_or_close(struct fusd_file_info *file)
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{
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return 0; /* opens and closes always succeed */
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}
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struct fusd_file_operations echo_fops = {
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open: do_open_or_close,
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read: echo_read,
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write: echo_write,
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close: do_open_or_close
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};
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int main(int argc, char *argv[])
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{
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if (fusd_register("/dev/echo", "misc", "echo", 0666, NULL, &echo_fops) < 0) {
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perror("register of /dev/echo failed");
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exit(1);
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}
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fprintf(stderr, "calling fusd_run...\n");
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fusd_run();
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return 0;
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}
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