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Makes libossaudio use sndio instead of the kernel mixer(4) interface.

Programs will see the device handled by sndiod (instead of the first
one) and will always get access at least the sndiod master level
control. If present, hardware master input and output volumes are
exposed as well.

feedback from landry and sthen, "do it" deraadt

/*	$OpenBSD: ossaudio.c,v 1.21 2020/04/02 19:57:10 ratchov Exp $	*/
/*	$NetBSD: ossaudio.c,v 1.14 2001/05/10 01:53:48 augustss Exp $	*/

/*-
 * Copyright (c) 1997 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This is an OSS (Linux) sound API emulator.
 * It provides the essentials of the API.
 */

#include <stdarg.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <poll.h>
#include <sndio.h>
#include <stdlib.h>
#include <stdio.h>
#include "soundcard.h"

#ifdef DEBUG
#define DPRINTF(...) do { fprintf(stderr, __VA_ARGS__); } while (0)
#else
#define DPRINTF(...) do {} while (0)
#endif

#define GET_DEV(com) ((com) & 0xff)
#define INTARG (*(int*)argp)

struct control {
	struct control *next;
	int type;		/* one of SOUND_MIXER_xxx */
	int chan;		/* 0 -> left, 1 -> right, -1 -> mono */
	int addr;		/* sioctl control id */
	int value;		/* current value */
	int max;
};

static int mixer_ioctl(int, unsigned long, void *);

static int initialized;
static struct control *controls;
static struct sioctl_hdl *hdl;
static char *dev_name = SIO_DEVANY;
static struct pollfd *pfds;

int
_oss_ioctl(int fd, unsigned long com, ...)
{
	va_list ap;
	void *argp;

	va_start(ap, com);
	argp = va_arg(ap, void *);
	va_end(ap);
	if (IOCGROUP(com) == 'P')
		return ENOTTY;
	else if (IOCGROUP(com) == 'M')
		return mixer_ioctl(fd, com, argp);
	else
		return (ioctl)(fd, com, argp);
}

/*
 * new control
 */
static void
mixer_ondesc(void *unused, struct sioctl_desc *d, int val)
{
	struct control *i, **pi;
	int type;

	if (d == NULL)
		return;

	/*
	 * delete existing control with the same address
	 */
	for (pi = &controls; (i = *pi) != NULL; pi = &i->next) {
		if (d->addr == i->addr) {
			*pi = i->next;
			free(i);
			break;
		}
	}

	/*
	 * we support only numeric "level" controls, first 2 channels
	 */
	if (d->type != SIOCTL_NUM || d->node0.unit >= 2 ||
	    strcmp(d->func, "level") != 0)
		return;

	/*
	 * We expose top-level input.level and output.level as OSS
	 * volume and microphone knobs. By default sndiod exposes
	 * the underlying hardware knobs as hw/input.level and
	 * hw/output.level that we map to OSS gain controls. This
	 * ensures useful knobs are exposed no matter if sndiod
	 * is running or not.
	 */ 
	if (d->group[0] == 0) {
		if (strcmp(d->node0.name, "output") == 0)
			type = SOUND_MIXER_VOLUME;
		else if (strcmp(d->node0.name, "input") == 0)
			type = SOUND_MIXER_MIC;
		else
			return;
	} else if (strcmp(d->group, "hw") == 0) {
		if (strcmp(d->node0.name, "output") == 0)
			type = SOUND_MIXER_OGAIN;
		else if (strcmp(d->node0.name, "input") == 0)
			type = SOUND_MIXER_IGAIN;
		else
			return;
	} else
		return;

	i = malloc(sizeof(struct control));
	if (i == NULL) {
		DPRINTF("%s: cannot allocate control\n", __func__);		
		return;
	}

	i->addr = d->addr;
	i->chan = d->node0.unit;
	i->max = d->maxval;
	i->value = val;
	i->type = type;
	i->next = controls;
	controls = i;
	DPRINTF("%s: %d: used as %d, chan = %d, value = %d\n", __func__,
	    i->addr, i->type, i->chan, i->value);
}

/*
 * control value changed
 */
static void
mixer_onval(void *unused, unsigned int addr, unsigned int value)
{
	struct control *c;

	for (c = controls; ; c = c->next) {
		if (c == NULL) {
			DPRINTF("%s: %d: change ignored\n", __func__, addr);
			return;
		}
		if (c->addr == addr)
			break;
	}

	DPRINTF("%s: %d: changed to %d\n", __func__, addr, value);
	c->value = value;
}

static int
mixer_init(void)
{
	if (initialized)
		return hdl != NULL;

	initialized = 1;

	hdl = sioctl_open(dev_name, SIOCTL_READ | SIOCTL_WRITE, 0);
	if (hdl == NULL) {
		DPRINTF("%s: cannot open audio control device\n", __func__);
		return 0;
	}

	pfds = calloc(sioctl_nfds(hdl), sizeof(struct pollfd));
	if (pfds == NULL) {
		DPRINTF("%s: cannot allocate pfds\n", __func__);
		goto bad_close;
	}

	if (!sioctl_ondesc(hdl, mixer_ondesc, NULL)) {
		DPRINTF("%s: cannot get controls descriptions\n", __func__);
		goto bad_free;
	}

	if (!sioctl_onval(hdl, mixer_onval, NULL)) {
		DPRINTF("%s: cannot get controls values\n", __func__);
		goto bad_free;
	}

	return 1;

bad_free:
	free(pfds);
bad_close:
	sioctl_close(hdl);
	return 0;
}

static int
mixer_ioctl(int fd, unsigned long com, void *argp)
{
	struct control *c;
	struct mixer_info *omi;
	int idat = 0;
	int v, n;

	if (!mixer_init()) {
		DPRINTF("%s: not initialized\n", __func__);
		errno = EIO;
		return -1;
	}

	n = sioctl_pollfd(hdl, pfds, POLLIN);
	if (n > 0) {
		n = poll(pfds, n, 0);
		if (n == -1)
			return -1;
		if (n > 0)
			sioctl_revents(hdl, pfds);
	}

	switch (com) {
	case OSS_GETVERSION:
		idat = SOUND_VERSION;
		break;
	case SOUND_MIXER_INFO:
	case SOUND_OLD_MIXER_INFO:
		omi = argp;
		if (com == SOUND_MIXER_INFO)
			omi->modify_counter = 1;
		strlcpy(omi->id, dev_name, sizeof omi->id);
		strlcpy(omi->name, dev_name, sizeof omi->name);
		return 0;
	case SOUND_MIXER_READ_RECSRC:
	case SOUND_MIXER_READ_RECMASK:
		idat = 0;
		for (c = controls; c != NULL; c = c->next)
			idat |= 1 << c->type;
		idat &= (1 << SOUND_MIXER_MIC) | (1 << SOUND_MIXER_IGAIN);
		DPRINTF("%s: SOUND_MIXER_READ_RECSRC: %d\n", __func__, idat);
		break;
	case SOUND_MIXER_READ_DEVMASK:
		idat = 0;
		for (c = controls; c != NULL; c = c->next)
			idat |= 1 << c->type;
		DPRINTF("%s: SOUND_MIXER_READ_DEVMASK: %d\n", __func__, idat);
		break;
	case SOUND_MIXER_READ_STEREODEVS:
		idat = 0;
		for (c = controls; c != NULL; c = c->next) {
			if (c->chan == 1)
				idat |= 1 << c->type;
		}
		DPRINTF("%s: SOUND_MIXER_STEREODEVS: %d\n", __func__, idat);
		break;
	case SOUND_MIXER_READ_CAPS:
		idat = 0;
		DPRINTF("%s: SOUND_MIXER_READ_CAPS: %d\n", __func__, idat);
		break;
	case SOUND_MIXER_WRITE_RECSRC:
	case SOUND_MIXER_WRITE_R_RECSRC:
		DPRINTF("%s: SOUND_MIXER_WRITE_RECSRC\n", __func__);
		errno = EINVAL;
		return -1;
	default:
		if (MIXER_READ(SOUND_MIXER_FIRST) <= com &&
		    com < MIXER_READ(SOUND_MIXER_NRDEVICES)) {
		doread:
			idat = 0;
			n = GET_DEV(com);
			for (c = controls; c != NULL; c = c->next) {
				if (c->type != n)
					continue;
				v = (c->value * 100 + c->max / 2) / c->max;
				if (c->chan == 1)
					v <<= 8;
				idat |= v;
			}
			DPRINTF("%s: MIXER_READ: %d: 0x%04x\n",
			    __func__, n, idat);
			break;
		} else if ((MIXER_WRITE_R(SOUND_MIXER_FIRST) <= com &&
			   com < MIXER_WRITE_R(SOUND_MIXER_NRDEVICES)) ||
			   (MIXER_WRITE(SOUND_MIXER_FIRST) <= com &&
			   com < MIXER_WRITE(SOUND_MIXER_NRDEVICES))) {
			idat = INTARG;
			n = GET_DEV(com);
			for (c = controls; c != NULL; c = c->next) {
				if (c->type != n)
					continue;
				v = idat;
				if (c->chan == 1)
					v >>= 8;
				v &= 0xff;
				if (v > 100)
					v = 100;
				v = (v * c->max + 50) / 100;
				sioctl_setval(hdl, c->addr, v);
				DPRINTF("%s: MIXER_WRITE: %d: %d\n",
				    __func__, n, v);
			}
			if (MIXER_WRITE(SOUND_MIXER_FIRST) <= com &&
			   com < MIXER_WRITE(SOUND_MIXER_NRDEVICES))
				return 0;
			goto doread;
		} else {
			errno = EINVAL;
			return -1;
		}
	}

	INTARG = idat;
	return 0;
}