sound/core/oss/io.c

Source file repositories/reference/linux-study-clean/sound/core/oss/io.c

File Facts

System
Linux kernel
Corpus path
sound/core/oss/io.c
Extension
.c
Size
3700 bytes
Lines
127
Domain
Driver Families
Bucket
sound/core
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: LGPL-2.0+
/*
 *  PCM I/O Plug-In Interface
 *  Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz>
 */
  
#include <linux/time.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include "pcm_plugin.h"

#define pcm_write(plug,buf,count) snd_pcm_oss_write3(plug,buf,count,1)
#define pcm_writev(plug,vec,count) snd_pcm_oss_writev3(plug,vec,count)
#define pcm_read(plug,buf,count) snd_pcm_oss_read3(plug,buf,count,1)
#define pcm_readv(plug,vec,count) snd_pcm_oss_readv3(plug,vec,count)

/*
 *  Basic io plugin
 */
 
static snd_pcm_sframes_t io_playback_transfer(struct snd_pcm_plugin *plugin,
				    const struct snd_pcm_plugin_channel *src_channels,
				    struct snd_pcm_plugin_channel *dst_channels,
				    snd_pcm_uframes_t frames)
{
	if (snd_BUG_ON(!plugin))
		return -ENXIO;
	if (snd_BUG_ON(!src_channels))
		return -ENXIO;
	if (plugin->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED) {
		return pcm_write(plugin->plug, src_channels->area.addr, frames);
	} else {
		int channel, channels = plugin->dst_format.channels;
		void **bufs = (void**)plugin->extra_data;
		if (snd_BUG_ON(!bufs))
			return -ENXIO;
		for (channel = 0; channel < channels; channel++) {
			if (src_channels[channel].enabled)
				bufs[channel] = src_channels[channel].area.addr;
			else
				bufs[channel] = NULL;
		}
		return pcm_writev(plugin->plug, bufs, frames);
	}
}
 
static snd_pcm_sframes_t io_capture_transfer(struct snd_pcm_plugin *plugin,
				   const struct snd_pcm_plugin_channel *src_channels,
				   struct snd_pcm_plugin_channel *dst_channels,
				   snd_pcm_uframes_t frames)
{
	if (snd_BUG_ON(!plugin))
		return -ENXIO;
	if (snd_BUG_ON(!dst_channels))
		return -ENXIO;
	if (plugin->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED) {
		return pcm_read(plugin->plug, dst_channels->area.addr, frames);
	} else {
		int channel, channels = plugin->dst_format.channels;
		void **bufs = (void**)plugin->extra_data;
		if (snd_BUG_ON(!bufs))
			return -ENXIO;
		for (channel = 0; channel < channels; channel++) {
			if (dst_channels[channel].enabled)
				bufs[channel] = dst_channels[channel].area.addr;
			else
				bufs[channel] = NULL;
		}
		return pcm_readv(plugin->plug, bufs, frames);
	}
	return 0;
}
 
static snd_pcm_sframes_t io_src_channels(struct snd_pcm_plugin *plugin,
			     snd_pcm_uframes_t frames,
			     struct snd_pcm_plugin_channel **channels)
{
	int err;
	unsigned int channel;
	struct snd_pcm_plugin_channel *v;
	err = snd_pcm_plugin_client_channels(plugin, frames, &v);
	if (err < 0)
		return err;
	*channels = v;
	if (plugin->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED) {
		for (channel = 0; channel < plugin->src_format.channels; ++channel, ++v)
			v->wanted = 1;
	}
	return frames;

Annotation

Implementation Notes