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![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>
41 lines
1.5 KiB
C
41 lines
1.5 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 PLAYBACK_H
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#define PLAYBACK_H
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#include <sound/pcm.h>
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#include "driver.h"
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/*
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* When the TonePort is used with jack in full duplex mode and the outputs are
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* not connected, the software monitor produces an ugly noise since everything
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* written to the output buffer (i.e., the input signal) will be repeated in
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* the next period (sounds like a delay effect). As a workaround, the output
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* buffer is cleared after the data have been read, but there must be a better
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* solution. Until one is found, this workaround can be used to fix the
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* problem.
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*/
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#define USE_CLEAR_BUFFER_WORKAROUND 1
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extern struct snd_pcm_ops snd_line6_playback_ops;
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extern int line6_create_audio_out_urbs(struct snd_line6_pcm *line6pcm);
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extern void line6_free_playback_buffer(struct snd_line6_pcm *line6pcm);
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extern int line6_submit_audio_out_all_urbs(struct snd_line6_pcm *line6pcm);
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extern void line6_unlink_audio_out_urbs(struct snd_line6_pcm *line6pcm);
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extern void line6_unlink_wait_clear_audio_out_urbs(struct snd_line6_pcm
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*line6pcm);
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extern void line6_wait_clear_audio_out_urbs(struct snd_line6_pcm *line6pcm);
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extern int snd_line6_playback_trigger(struct snd_line6_pcm *line6pcm, int cmd);
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#endif
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