![Markus Grabner](/assets/img/avatar_default.png)
There are several features of the Line6 USB driver which require PCM data to be exchanged with the device: *) PCM playback and capture via ALSA *) software monitoring (for devices without hardware monitoring) *) optional impulse response measurement However, from the device's point of view, there is just a single capture and playback stream, which must be shared between these subsystems. It is therefore necessary to maintain the state of the subsystems with respect to PCM usage. We define several constants of the form LINE6_BIT_PCM_<subsystem>_<direction>_<resource> with the following meanings: *) <subsystem> is one of -) ALSA: PCM playback and capture via ALSA -) MONITOR: software monitoring -) IMPULSE: optional impulse response measurement *) <direction> is one of -) PLAYBACK: audio output (from host to device) -) CAPTURE: audio input (from device to host) *) <resource> is one of -) BUFFER: buffer required by PCM data stream -) STREAM: actual PCM data stream The subsystems call line6_pcm_acquire() to acquire the (shared) resources needed for a particular operation (e.g., allocate the buffer for ALSA playback or start the capture stream for software monitoring). When a resource is no longer needed, it is released by calling line6_pcm_release(). Buffer allocation and stream startup are handled separately to allow the ALSA kernel driver to perform them at appropriate places (since the callback which starts a PCM stream is not allowed to sleep). Signed-off-by: Markus Grabner <grabner@icg.tugraz.at> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
36 lines
1.2 KiB
C
36 lines
1.2 KiB
C
/*
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* Line6 Linux USB driver - 0.9.1beta
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*
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* Copyright (C) 2004-2010 Markus Grabner (grabner@icg.tugraz.at)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2.
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*
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*/
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#ifndef CAPTURE_H
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#define CAPTURE_H
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#include <sound/pcm.h>
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#include "driver.h"
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#include "pcm.h"
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extern struct snd_pcm_ops snd_line6_capture_ops;
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extern void line6_capture_copy(struct snd_line6_pcm *line6pcm, char *fbuf,
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int fsize);
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extern void line6_capture_check_period(struct snd_line6_pcm *line6pcm,
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int length);
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extern int line6_create_audio_in_urbs(struct snd_line6_pcm *line6pcm);
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extern void line6_free_capture_buffer(struct snd_line6_pcm *line6pcm);
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extern int line6_submit_audio_in_all_urbs(struct snd_line6_pcm *line6pcm);
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extern void line6_unlink_audio_in_urbs(struct snd_line6_pcm *line6pcm);
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extern void line6_unlink_wait_clear_audio_in_urbs(struct snd_line6_pcm
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*line6pcm);
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extern void line6_wait_clear_audio_in_urbs(struct snd_line6_pcm *line6pcm);
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extern int snd_line6_capture_trigger(struct snd_line6_pcm *line6pcm, int cmd);
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#endif
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