1/**
2 * \file pcm/pcm_empty.c
3 * \ingroup PCM_Plugins
4 * \brief PCM Null Plugin Interface
5 * \author Jaroslav Kysela <perex@perex.cz>
6 * \date 2006
7 */
8/*
9 *  PCM - Null plugin
10 *  Copyright (c) 2006 by Jaroslav Kysela <perex@perex.cz>
11 *
12 *
13 *   This library is free software; you can redistribute it and/or modify
14 *   it under the terms of the GNU Lesser General Public License as
15 *   published by the Free Software Foundation; either version 2.1 of
16 *   the License, or (at your option) any later version.
17 *
18 *   This program is distributed in the hope that it will be useful,
19 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
20 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
21 *   GNU Lesser General Public License for more details.
22 *
23 *   You should have received a copy of the GNU Lesser General Public
24 *   License along with this library; if not, write to the Free Software
25 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
26 *
27 */
28
29#include "pcm_local.h"
30#include "pcm_plugin.h"
31
32#ifndef PIC
33/* entry for static linking */
34const char *_snd_module_pcm_empty = "";
35#endif
36
37/*! \page pcm_plugins
38
39\section pcm_plugins_null Plugin: Null
40
41This plugin discards contents of a PCM stream or creates a stream with zero
42samples.
43
44Note: This implementation uses devices /dev/null (playback, must be writable)
45and /dev/full (capture, must be readable).
46
47\code
48pcm.name {
49        type null               # Null PCM
50}
51\endcode
52
53\subsection pcm_plugins_null_funcref Function reference
54
55<UL>
56  <LI>_snd_pcm_empty_open()
57</UL>
58
59*/
60
61/**
62 * \brief Creates a new Empty PCM
63 * \param pcmp Returns created PCM handle
64 * \param name Name of PCM
65 * \param root Root configuration node
66 * \param conf Configuration node with empty PCM description
67 * \param stream Stream type
68 * \param mode Stream mode
69 * \retval zero on success otherwise a negative error code
70 * \warning Using of this function might be dangerous in the sense
71 *          of compatibility reasons. The prototype might be freely
72 *          changed in future.
73 */
74int _snd_pcm_empty_open(snd_pcm_t **pcmp, const char *name ATTRIBUTE_UNUSED,
75		        snd_config_t *root, snd_config_t *conf,
76		        snd_pcm_stream_t stream, int mode)
77{
78	snd_config_t *slave = NULL, *sconf;
79	snd_config_iterator_t i, next;
80	int err;
81
82	snd_config_for_each(i, next, conf) {
83		snd_config_t *n = snd_config_iterator_entry(i);
84		const char *id;
85		if (snd_config_get_id(n, &id) < 0)
86			continue;
87		if (snd_pcm_conf_generic_id(id))
88			continue;
89		if (strcmp(id, "slave") == 0) {
90			slave = n;
91			continue;
92		}
93		SNDERR("Unknown field %s", id);
94		return -EINVAL;
95	}
96	if (!slave) {
97		SNDERR("slave is not defined");
98		return -EINVAL;
99	}
100	err = snd_pcm_slave_conf(root, slave, &sconf, 0);
101	if (err < 0)
102		return err;
103	err = snd_pcm_open_named_slave(pcmp, name, root, sconf, stream,
104				       mode, conf);
105	snd_config_delete(sconf);
106	return err;
107}
108#ifndef DOC_HIDDEN
109SND_DLSYM_BUILD_VERSION(_snd_pcm_empty_open, SND_PCM_DLSYM_VERSION);
110#endif
111