cregit-Linux how code gets into the kernel

Release 4.8 sound/drivers/pcm-indirect2.h

Directory: sound/drivers
 * Helper functions for indirect PCM data transfer to a simple FIFO in
 * hardware (small, no possibility to read "hardware io position",
 * updating position done by interrupt, ...)
 *  Copyright (c) by 2007  Joachim Foerster <>
 *  Based on "pcm-indirect.h" (alsa-driver-1.0.13) by
 *  Copyright (c) by Takashi Iwai <>
 *                   Jaroslav Kysela <>
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   GNU General Public License for more details.
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.



/* struct snd_pcm_substream, struct snd_pcm_runtime, snd_pcm_uframes_t */
#include <sound/pcm.h>

/* Debug options for code which may be removed completely in a final version */

/* turn on some "statistics" about the
                                   * process of copying bytes from the
                                   * intermediate buffer to the hardware
                                   * fifo and the other way round

struct snd_pcm_indirect2 {
unsigned int hw_buffer_size;  /* Byte size of hardware buffer */
int hw_ready;		      /* playback: 1 = hw fifo has room left,
                                       * 0 = hw fifo is full
unsigned int min_multiple;
int min_periods;	      /* counts number of min. periods until
                                       * min_multiple is reached
int min_period_count;	      /* counts bytes to count number of
                                       * min. periods

unsigned int sw_buffer_size;  /* Byte size of software buffer */

	/* sw_data: position in intermediate buffer, where we will read (or
         *          write) from/to next time (to transfer data to/from HW)
unsigned int sw_data;         /* Offset to next dst (or src) in sw
                                       * ring buffer
	/* easiest case (playback):
         * sw_data is nearly the same as ~ runtime->control->appl_ptr, with the
         * exception that sw_data is "behind" by the number if bytes ALSA wrote
         * to the intermediate buffer last time.
         * A call to ack() callback synchronizes both indirectly.

	/* We have no real sw_io pointer here. Usually sw_io is pointing to the
         * current playback/capture position _inside_ the hardware. Devices
         * with plain FIFOs often have no possibility to publish this position.
         * So we say: if sw_data is updated, that means bytes were copied to
         * the hardware, we increase sw_io by that amount, because there have
         * to be as much bytes which were played. So sw_io will stay behind
         * sw_data all the time and has to converge to sw_data at the end of
         * playback.
unsigned int sw_io;           /* Current software pointer in bytes */

	/* sw_ready: number of bytes ALSA copied to the intermediate buffer, so
         * it represents the number of bytes which wait for transfer to the HW
int sw_ready;		  /* Bytes ready to be transferred to/from hw */

	/* appl_ptr: last known position of ALSA (where ALSA is going to write
         * next time into the intermediate buffer
snd_pcm_uframes_t appl_ptr;   /* Last seen appl_ptr */

unsigned int bytes2hw;
int check_alignment;

unsigned int zeros2hw;
unsigned int mul_elapsed;
unsigned int mul_elapsed_real;
unsigned long firstbytetime;
unsigned long lastbytetime;
unsigned long firstzerotime;
unsigned int byte_sizes[64];
unsigned int zero_sizes[64];
unsigned int min_adds[8];
unsigned int mul_adds[8];
unsigned int zero_times[3750];	/* = 15s */
unsigned int zero_times_saved;
unsigned int zero_times_notsaved;
unsigned int irq_occured;
unsigned int pointer_calls;
unsigned int lastdifftime;

typedef size_t (*snd_pcm_indirect2_copy_t) (struct snd_pcm_substream *substream,
					   struct snd_pcm_indirect2 *rec,
					   size_t bytes);

typedef size_t (*snd_pcm_indirect2_zero_t) (struct snd_pcm_substream *substream,
					   struct snd_pcm_indirect2 *rec);

void snd_pcm_indirect2_stat(struct snd_pcm_substream *substream,
				   struct snd_pcm_indirect2 *rec);

snd_pcm_indirect2_pointer(struct snd_pcm_substream *substream,
			  struct snd_pcm_indirect2 *rec);
snd_pcm_indirect2_playback_interrupt(struct snd_pcm_substream *substream,
				     struct snd_pcm_indirect2 *rec,
				     snd_pcm_indirect2_copy_t copy,
				     snd_pcm_indirect2_zero_t zero);
snd_pcm_indirect2_capture_interrupt(struct snd_pcm_substream *substream,
				    struct snd_pcm_indirect2 *rec,
				    snd_pcm_indirect2_copy_t copy,
				    snd_pcm_indirect2_zero_t null);

#endif /* __SOUND_PCM_INDIRECT2_H */

Overall Contributors

joachim foersterjoachim foerster282100.00%1100.00%
Directory: sound/drivers
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